Because of my travel to the STISS (THORPEX) in Germany from 12/1-12/8, I will not be able to do a writing until the following week at the earliest. However, Klaus and I did post another weather-climate discussion on the ESRL/PSD MJO web page at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
Predictive insights are offerred in Section 2. Also, since I am involved with the Hydrometeorological Testbed project (HMT), I will be at ESRL/PSD during approximately January and March 2007 (~1 month each). During those times we plan on short postings to this blog at least every other day. By then we will know if we get GSDM Stage 3 or "something else". Right now uncertainty remains tremendously high.
Ed Berry
Thursday, November 30, 2006
Thursday, November 23, 2006
New World Atmosphere Winter Before El-Nino???
Please see past postings for web site links. In this writing I am going to post a version of a draft of Section 2 (Predictive Insights) which will appear in our next weather-climate discussion for the ESRL/PSD MJO web site.
Global tropical SSTs remain well above average across the Indian Ocean (IO) and from around the date line to the west coast of South America, with weekly mean magnitudes of 1-3C along the equatorial cold tongue. Warmth also persists across the North Atlantic, particularly from the Caribbean to the west coast of Africa. At depth the positive anomalies along the equatorial east Pacific extend to about 250m with values to around 5C at 125m at 120W meaning a deeper than normal thermocline assisted by the Kelvin wave currently propagating eastward along it. Anomalies south of Indonesia remain slighly below average while their spatial distribution decreases. During the past week equatorial SST tendencies have generally been positive with magnitudes ~.5-1.0C. Part of this SST distribution is from a well defined and currently strengthening warm phase of ENSO.
The following are links to ENSO discussions:
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
Per full disk satellite imagery two prominent areas of tropical convective forcing are evident. One is located over the warm SSTs around the equatorial date line with the other larger region centered on the IO (including central and southern Africa), with latest 3-day averaged OLRA ~minus 70-90 W/m**2. The recent Western Hemisphere tropical forcing linked to a convectively coupled Kelvin wave has lost coherence. From animations such as 150mb and 250mb daily mean vector wind anomalies, the IO forcing appears to be organizing into an MJO. There is now the quadrapole of upstream twin subtropical anticyclones (and low level westerlies) with downstream cyclonic anomalies, and these features are interacting with the extratropics through wave energy dispersion processes. In fact, the latest plot on the Wheeler diagram shows a projection well above 1 sigma and there is also a projection onto the coherent modes Hovmollers. Finally, a loose phase speed computation has a movement of roughly 5m/s or about 20 deg of longitude during a 5-day period from November 15-20.
The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. Since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~25-30N) while being replaced by easterlies. During early November an anomalous combined jet did extend across the North PacificOcean ~35N meaning a GSDM Stage 3 situation was briefly present, and this was about the time excessive rainfall across the Pacific Northwest commenced. Some of this westerly flow did make it to the surface augmenting deep tropical moisture transport from the date line region to the northwestern USA. Additionally, upper tropospheric divergent outflows from the African and IO convection through interactions with baroclinic wave packets led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking assisted with the dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm) until about a week ago.
Careful examination of the animations shows that a recent Rossby wave energy dispersion linked to the MJO arcing into the Southern Hemisphere extratropics contributed to the flare-up of the South Pacific tropical convection. This region of forcing has been expanding back to the west-northwest into northern Indonesia during the last few days. Moreover, convectively coupled Kelvin waves emanating from the MJO along with the expanding date line/South Pacific convection have allowed some filling in to occur meaning a band of tropical thunderstorm clusters across northern Indonesia linking the 2 regions. Twin upper tropospheric anticyclones supporting cross equatorial flow from the Southern Hemisphere are also present around the date line. The latter are supporting the linkage of a subtropical jet with the trough currently moving into the western USA.
Global relative AAM is about 1 sigma below the 1968-1997 reanalysis data climatology as of November 20th. Contributions to this low AAM are coming from the zonal mean easterly anomalies across the deep tropics and the Southern Hemisphere subtropical atmosphere as well as ~40N. The latter can be linked to the recent blocking episodes from Greenland to Kamchatka. Global relative AAM tendency reached a negative minimum of ~minus 20 Hadleys around November 16th only to be approaching plus 20 Hadleys on the 20th. Positive zonal mean tendencies of around 2 Hadleys were appearing from the equator to around 20N with weakly negative values across the Arctic (latest AAM plots here), with the former believed to be linked with South Pacific tropical convective flare-up discussed above. The contributions of the mountain and frictional torques to the global AAM budget were ~plus 10-15 Hadleys each. However, there were significant zonal mean variations. For instance, the mountain torque had magnitudes of ~2 Hadleys and a minus-plus-minus distribution from 30-90N.
GSDM Stage 4 has best described the weather-climate situation for roughly the past couple of weeks. However, given the MJO signal, careful interpretation of the AAM plots and critical daily monitoring, a transition to GSDM Stage 1 may be in progress. For instance, animations do show the recent Kamchatka blocking becoming "dislodged"and is tied to a Rossby wave energy dispersion from the IO convection. As shown by most models (but with large differences in the details) the trough which has been present across the Gulf of Alaska is about to deepen into the western USA (leading to a greater projection onto the negative phase of the PNA). Arctic air has been building up across Alaska and northwest Canada for the last several weeks, and this trough will have that airmass as a cold air source. The latter has been discussed as a possibility in previous postings.
However, where we go from here remains tremendously uncertain, especially given the seasonal cycle (and other issues such as high latitude blocking). There are also going to be impacts from tropical convective flare-ups until if and when "El-Nino kicks in". For instance, the positive AAM tendency we are now seeing I think is directly attributable to the current "MJO forced flare-up". A probable thought may be for MJO forcing to consolidate with the date line thunderstorm clusters leading to a large region of intense tropical rainfall extending from near the Philippines to the South Pacific centered ~150E by late week 2 or week 3. This region may then stall before shifting east-southeast toward the central Pacific/SPCZ by early January 2007. Thus perhaps GSDM Stage 1 with subtropical jets may be the case for the weather-climate situation through week 2, followed by GSDM Stage 2 for much of (mid-late?) December. Afterwards, GSDM Stage 3 may appear, which is "typical" during the warm phase of ENSO. In the USA outlooks that follow, confidence is below average for week 1, then as low as it gets for weeks 2-3.
Week 1 (24-30 November 2006): GSDM Stage 1 with a moist subtropical jet is most probable. This situation generally favors an active weather regime for the Rockies and Plains, with a southwest-northeast storm track across the central USA. An important issue is how soon deep tropical moisture transport through the Gulf of Mexico can resume after the recent surges of cool dry air. Latest observations suggest low level moistening is occurring across the Gulf of Mexico. Most models do predict baroclinic development on the Plains by around the middle of next week, but with still serious phase and amplitude issues. They are "catching-up" to the changing tropical convective forcing and other processes. A thought to offer would be a slower and more amplified solution for trough development, and the models are now trending there. In any case, bitterly cold Arctic air is likely to penetrate into the Rockies and Plains by the end of this period while the Deep South warms up. Depending on the details, portions of the Rockies and Plains may have severe winter weather conditions while severe local storms become a concern for the locations such as the south central states to the Ohio Valley.
I also want to make special mention of the still on-going tropical cyclone risks across the central Pacific and possibly other regions. Satellite pictures show evidence of development trying to occur west-northwest of the equatorial date line. Locations such as the Philippines may be impacted later this period. Tropical cyclone Yani is already in progress across the South Pacific islands, and more development may follow. Finally, locations across the Indian Ocean may become at risk for tropical cyclone development as the MJO slowly moves east.
Week 2 (1 - 7 December 2006): Same as week 1, but with the usual synoptic variations in amplitude. Perhaps another episode of baroclinic development across the Rockies and Plains may occur toward the end of this period. I do not think the week 1 storm system will be the "last western/central USA" trough. In fact, the stronger and slower moving troughs may not be until the last half of December, particularly if a transition from GSDM Stage 1-2 occurs.
Week 3 (8 -14 December 2006): See week 2. We may have a period during weeks 4-6 of extremely cold air covering particularly the central USA should a mature GSDM Stage 2 evolve. That may allow a snow pack to build across locations such as the Upper Mississippi Valley and Great Lakes. Given the magnitude of our warm ENSO (and other factors) I would be surprised not to see an anomalously strong combined jet ~30-35N extend from East Asia into the western USA (with split flow across North America) by ~ the middle of January 2007, which would be GSDM Stage 3. This would significantly increased the probability of high impact weather (heavy precipitation, high winds, etc.) for the USA west coast perhaps affecting California the most (other regions for hazards and weather understood).
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
I will try to do another posting before my trip to the STISS (THORPEX) in Germany.
Ed Berry
Global tropical SSTs remain well above average across the Indian Ocean (IO) and from around the date line to the west coast of South America, with weekly mean magnitudes of 1-3C along the equatorial cold tongue. Warmth also persists across the North Atlantic, particularly from the Caribbean to the west coast of Africa. At depth the positive anomalies along the equatorial east Pacific extend to about 250m with values to around 5C at 125m at 120W meaning a deeper than normal thermocline assisted by the Kelvin wave currently propagating eastward along it. Anomalies south of Indonesia remain slighly below average while their spatial distribution decreases. During the past week equatorial SST tendencies have generally been positive with magnitudes ~.5-1.0C. Part of this SST distribution is from a well defined and currently strengthening warm phase of ENSO.
The following are links to ENSO discussions:
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
Per full disk satellite imagery two prominent areas of tropical convective forcing are evident. One is located over the warm SSTs around the equatorial date line with the other larger region centered on the IO (including central and southern Africa), with latest 3-day averaged OLRA ~minus 70-90 W/m**2. The recent Western Hemisphere tropical forcing linked to a convectively coupled Kelvin wave has lost coherence. From animations such as 150mb and 250mb daily mean vector wind anomalies, the IO forcing appears to be organizing into an MJO. There is now the quadrapole of upstream twin subtropical anticyclones (and low level westerlies) with downstream cyclonic anomalies, and these features are interacting with the extratropics through wave energy dispersion processes. In fact, the latest plot on the Wheeler diagram shows a projection well above 1 sigma and there is also a projection onto the coherent modes Hovmollers. Finally, a loose phase speed computation has a movement of roughly 5m/s or about 20 deg of longitude during a 5-day period from November 15-20.
The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. Since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~25-30N) while being replaced by easterlies. During early November an anomalous combined jet did extend across the North PacificOcean ~35N meaning a GSDM Stage 3 situation was briefly present, and this was about the time excessive rainfall across the Pacific Northwest commenced. Some of this westerly flow did make it to the surface augmenting deep tropical moisture transport from the date line region to the northwestern USA. Additionally, upper tropospheric divergent outflows from the African and IO convection through interactions with baroclinic wave packets led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking assisted with the dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm) until about a week ago.
Careful examination of the animations shows that a recent Rossby wave energy dispersion linked to the MJO arcing into the Southern Hemisphere extratropics contributed to the flare-up of the South Pacific tropical convection. This region of forcing has been expanding back to the west-northwest into northern Indonesia during the last few days. Moreover, convectively coupled Kelvin waves emanating from the MJO along with the expanding date line/South Pacific convection have allowed some filling in to occur meaning a band of tropical thunderstorm clusters across northern Indonesia linking the 2 regions. Twin upper tropospheric anticyclones supporting cross equatorial flow from the Southern Hemisphere are also present around the date line. The latter are supporting the linkage of a subtropical jet with the trough currently moving into the western USA.
Global relative AAM is about 1 sigma below the 1968-1997 reanalysis data climatology as of November 20th. Contributions to this low AAM are coming from the zonal mean easterly anomalies across the deep tropics and the Southern Hemisphere subtropical atmosphere as well as ~40N. The latter can be linked to the recent blocking episodes from Greenland to Kamchatka. Global relative AAM tendency reached a negative minimum of ~minus 20 Hadleys around November 16th only to be approaching plus 20 Hadleys on the 20th. Positive zonal mean tendencies of around 2 Hadleys were appearing from the equator to around 20N with weakly negative values across the Arctic (latest AAM plots here), with the former believed to be linked with South Pacific tropical convective flare-up discussed above. The contributions of the mountain and frictional torques to the global AAM budget were ~plus 10-15 Hadleys each. However, there were significant zonal mean variations. For instance, the mountain torque had magnitudes of ~2 Hadleys and a minus-plus-minus distribution from 30-90N.
GSDM Stage 4 has best described the weather-climate situation for roughly the past couple of weeks. However, given the MJO signal, careful interpretation of the AAM plots and critical daily monitoring, a transition to GSDM Stage 1 may be in progress. For instance, animations do show the recent Kamchatka blocking becoming "dislodged"and is tied to a Rossby wave energy dispersion from the IO convection. As shown by most models (but with large differences in the details) the trough which has been present across the Gulf of Alaska is about to deepen into the western USA (leading to a greater projection onto the negative phase of the PNA). Arctic air has been building up across Alaska and northwest Canada for the last several weeks, and this trough will have that airmass as a cold air source. The latter has been discussed as a possibility in previous postings.
However, where we go from here remains tremendously uncertain, especially given the seasonal cycle (and other issues such as high latitude blocking). There are also going to be impacts from tropical convective flare-ups until if and when "El-Nino kicks in". For instance, the positive AAM tendency we are now seeing I think is directly attributable to the current "MJO forced flare-up". A probable thought may be for MJO forcing to consolidate with the date line thunderstorm clusters leading to a large region of intense tropical rainfall extending from near the Philippines to the South Pacific centered ~150E by late week 2 or week 3. This region may then stall before shifting east-southeast toward the central Pacific/SPCZ by early January 2007. Thus perhaps GSDM Stage 1 with subtropical jets may be the case for the weather-climate situation through week 2, followed by GSDM Stage 2 for much of (mid-late?) December. Afterwards, GSDM Stage 3 may appear, which is "typical" during the warm phase of ENSO. In the USA outlooks that follow, confidence is below average for week 1, then as low as it gets for weeks 2-3.
Week 1 (24-30 November 2006): GSDM Stage 1 with a moist subtropical jet is most probable. This situation generally favors an active weather regime for the Rockies and Plains, with a southwest-northeast storm track across the central USA. An important issue is how soon deep tropical moisture transport through the Gulf of Mexico can resume after the recent surges of cool dry air. Latest observations suggest low level moistening is occurring across the Gulf of Mexico. Most models do predict baroclinic development on the Plains by around the middle of next week, but with still serious phase and amplitude issues. They are "catching-up" to the changing tropical convective forcing and other processes. A thought to offer would be a slower and more amplified solution for trough development, and the models are now trending there. In any case, bitterly cold Arctic air is likely to penetrate into the Rockies and Plains by the end of this period while the Deep South warms up. Depending on the details, portions of the Rockies and Plains may have severe winter weather conditions while severe local storms become a concern for the locations such as the south central states to the Ohio Valley.
I also want to make special mention of the still on-going tropical cyclone risks across the central Pacific and possibly other regions. Satellite pictures show evidence of development trying to occur west-northwest of the equatorial date line. Locations such as the Philippines may be impacted later this period. Tropical cyclone Yani is already in progress across the South Pacific islands, and more development may follow. Finally, locations across the Indian Ocean may become at risk for tropical cyclone development as the MJO slowly moves east.
Week 2 (1 - 7 December 2006): Same as week 1, but with the usual synoptic variations in amplitude. Perhaps another episode of baroclinic development across the Rockies and Plains may occur toward the end of this period. I do not think the week 1 storm system will be the "last western/central USA" trough. In fact, the stronger and slower moving troughs may not be until the last half of December, particularly if a transition from GSDM Stage 1-2 occurs.
Week 3 (8 -14 December 2006): See week 2. We may have a period during weeks 4-6 of extremely cold air covering particularly the central USA should a mature GSDM Stage 2 evolve. That may allow a snow pack to build across locations such as the Upper Mississippi Valley and Great Lakes. Given the magnitude of our warm ENSO (and other factors) I would be surprised not to see an anomalously strong combined jet ~30-35N extend from East Asia into the western USA (with split flow across North America) by ~ the middle of January 2007, which would be GSDM Stage 3. This would significantly increased the probability of high impact weather (heavy precipitation, high winds, etc.) for the USA west coast perhaps affecting California the most (other regions for hazards and weather understood).
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
I will try to do another posting before my trip to the STISS (THORPEX) in Germany.
Ed Berry
Thursday, November 16, 2006
The Fist of El-Nino Continues (The Devil of the Tropics???)
Please see past postings for web site links. Also, I need to get very serious about paring down the length. Hopefully that will eventually translate to more frequent but short discussions
The overall spatial distribution of global tropical SSTS still has warm anomalies across the Indian Ocean (IO) and central/eastern tropical Pacific (~plus 1-3C) with cool (but weakening) values across southern Indonesia. Warm anomalies also persist across the Atlantic. Actual SSTS of 30C and higher remain present around the date line with 29C and warmer across the Indian Ocean. The positive SST anomalies along the equatorial cold tongue extend to depths of roughly 150m with magnitudes ~plus 4C meaning a deeper than normal thermocline. Part of this SST distribution is from a well defined warm ENSO signal although there are other contributions.
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
Loosely 3 regions of tropical convective forcing are present. Per full disk satellite imagery (and other monitoring tools) these areas are centered on the Americas, from Africa into the Indian Ocean and finally across the Southwest Pacific between the Polynesian Islands and Australia. There are indications the convection across the Indian Ocean may be evolving into a coherent eastward propagating feature, possibly an MJO. The tropical forcing across the South Pacific has shown a rapid increase during the last couple of days, likely a response to the warm SSTs (and interactions with the southern extratropics). The latter appears to be shifting to the west-northwest along the South Pacific Convergence Zone (SPCZ). The signal across the Western Hemisphere is at least partly a convectively coupled Kelvin wave.
The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. For instance, since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~30N) while being replaced by easterlies. Some of this poleward propagating westerly flow has made it to the surface (ex., the North Pacific Ocean) augmenting deep tropical moisture transport from the date line region to the USA Pacific Northwest where excessive rainfall has been occurring. Additionally, upper tropospheric divergent outflows from the African and Indian Ocean convection through interactions with baroclinic wave packets have led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking have assisted with the recent dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm).
GSDM Stage 4 best describes the current weather-climate situation. Where we go from here remains very uncertain. Yesterday I thought a slow transition from GSDM Stage 4-1 was most probable during the next 1-3 weeks. However, I am now concerned about the recent very rapid increase of convection across the South Pacific (daily monitoring is critical!). Respect needs to be given to the warm SSTs in that region. My own thought would be to “expect” a convectively coupled feature to shift east from the Indian Ocean into the west central Pacific during the next 1-3 weeks, possibly consolidating with a convectively coupled Rossby wave around ~120-140E north of the equator. The latter may evolve from the South Pacific.
Thus I think GSDM Stage 1 is probable by week 2, but may give way to Stage 2 by/during early December. One option with this scenario would be for an eastward shift of existing circulation anomalies, meaning full latitude troughs with Arctic air to impact the western USA sometime during week 2. By week 3 these troughs may shift toward the Plains while a ridge amplifies off the North American coast into Alaska. This would suggest an active regime for the Plains (all impacts should be understood) week 2 followed by perhaps much colder than normal temperatures for much of the country starting early December (centered on the Plains/Upper Mississippi Valley). Locations such as the Pacific Northwest may get a break from excessive precipitation by that time. We will see what happens; including if/when GSDM Stage 3 makes its appearance (extended low latitude North Pacific combined jet with split flow across North America – “typical” of a warm ENSO).
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
The overall spatial distribution of global tropical SSTS still has warm anomalies across the Indian Ocean (IO) and central/eastern tropical Pacific (~plus 1-3C) with cool (but weakening) values across southern Indonesia. Warm anomalies also persist across the Atlantic. Actual SSTS of 30C and higher remain present around the date line with 29C and warmer across the Indian Ocean. The positive SST anomalies along the equatorial cold tongue extend to depths of roughly 150m with magnitudes ~plus 4C meaning a deeper than normal thermocline. Part of this SST distribution is from a well defined warm ENSO signal although there are other contributions.
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
Loosely 3 regions of tropical convective forcing are present. Per full disk satellite imagery (and other monitoring tools) these areas are centered on the Americas, from Africa into the Indian Ocean and finally across the Southwest Pacific between the Polynesian Islands and Australia. There are indications the convection across the Indian Ocean may be evolving into a coherent eastward propagating feature, possibly an MJO. The tropical forcing across the South Pacific has shown a rapid increase during the last couple of days, likely a response to the warm SSTs (and interactions with the southern extratropics). The latter appears to be shifting to the west-northwest along the South Pacific Convergence Zone (SPCZ). The signal across the Western Hemisphere is at least partly a convectively coupled Kelvin wave.
The extratropics have been strongly impacted by this complex tropical forcing, with subsequent feedbacks. For instance, since late October zonal mean westerly wind anomalies (~5-15m/s at 200mb) have propagated from the tropical into the subtropical atmospheres (to ~30N) while being replaced by easterlies. Some of this poleward propagating westerly flow has made it to the surface (ex., the North Pacific Ocean) augmenting deep tropical moisture transport from the date line region to the USA Pacific Northwest where excessive rainfall has been occurring. Additionally, upper tropospheric divergent outflows from the African and Indian Ocean convection through interactions with baroclinic wave packets have led to the current blocking structure near Kamchatka. Per animations of 150mb and 250mb daily mean vector wind anomalies from ESRL/PSD, feedbacks from this blocking have assisted with the recent dynamic suppression of convection along and to the north of the equatorial date line (where SSTs are warm).
GSDM Stage 4 best describes the current weather-climate situation. Where we go from here remains very uncertain. Yesterday I thought a slow transition from GSDM Stage 4-1 was most probable during the next 1-3 weeks. However, I am now concerned about the recent very rapid increase of convection across the South Pacific (daily monitoring is critical!). Respect needs to be given to the warm SSTs in that region. My own thought would be to “expect” a convectively coupled feature to shift east from the Indian Ocean into the west central Pacific during the next 1-3 weeks, possibly consolidating with a convectively coupled Rossby wave around ~120-140E north of the equator. The latter may evolve from the South Pacific.
Thus I think GSDM Stage 1 is probable by week 2, but may give way to Stage 2 by/during early December. One option with this scenario would be for an eastward shift of existing circulation anomalies, meaning full latitude troughs with Arctic air to impact the western USA sometime during week 2. By week 3 these troughs may shift toward the Plains while a ridge amplifies off the North American coast into Alaska. This would suggest an active regime for the Plains (all impacts should be understood) week 2 followed by perhaps much colder than normal temperatures for much of the country starting early December (centered on the Plains/Upper Mississippi Valley). Locations such as the Pacific Northwest may get a break from excessive precipitation by that time. We will see what happens; including if/when GSDM Stage 3 makes its appearance (extended low latitude North Pacific combined jet with split flow across North America – “typical” of a warm ENSO).
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
Thursday, November 09, 2006
War Resumes Between Good and Evil
Please see past postings for web site links. Also, I need to get very serious about paring down the length. Hopefully that will translate to more frequent but short discussions.
The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~date line-South America with cool readings around Indonesia particularly south of the equator (see November 3rd posting for details). The warmest SSTs are still found along the equatorial date line with readings near 31C having ~2C anomalies. Equatorial SST and SST anomaly tendencies over the last week were ~minus 0.5-1.0C from around 140E-South America with some positive values across the Indian Ocean. Additionally, SST animations suggest there has been about a 10 degree eastward shift of the warm-cool-warm pattern discussed above during the last 2-3 months (seasonal cycle understood).
What is also interesting is the above average SSTs across the extratropical North Pacific Ocean basin. Granted, the latter have a secondary role to tropical SSTs (and different ocean-atmosphere dynamical processes – I need to keep down the length!). However, warm North Pacific SSTs is not consistent with a warm ENSO (in the composite sense), again keeping in mind the seasonal cycle. The latter could quickly change should GSDM Stage 3 evolve meaning a strong North Pacific jet with attendant East Asian cold air surges, etc., (which does not look probable for at least the next few weeks).
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
The point I want to emphasize in this writing is our two regions of tropical convective forcing is back. One region extends from equatorial Africa into the central Indian Ocean with the other centered ~0/160E. Yes, there are those who will invoke the Indian Ocean Dipole (IOD) notions and offer this situation is not all that unusual for a warm ENSO. While there is truth to these concepts, from my monitoring of trying to understand the dynamics of ocean-atmosphere forcing-response-feedbacks involving many scales of motion making use of the GSDM framework, the current weather-climate situation is much more complicated. From looking at animations of daily mean 150mb and 250mb vector wind anomalies I can clearly see the extratropics interacting with both regions of tropical forcing while helping to maintain them. We need to also remember this current warm ENSO evolved in a very random (and unpredictable) manner.
There is evidence from various tools (ex., Hovmoller plots of 250mb meridional wind anomalies in the 10-40N/S latitude bands) that subtropical wave trains are currently present in both hemispheres. I also have a suspicion that the tropical forcing over Africa into the Indian Ocean is trying to evolve into another MJO (the Wheeler phase space plot supports this). We will see. Global relative AAM tendency as of November 6th was ~minus 20 Hadleys as zonal mean westerly wind anomalies propagate poleward to ~30N/S while being replaced by zonal mean easterly wind anomalies throughout the deep tropics (magnitudes ~5-15m/s at 200mb). GSDM Stage 4 still best describes our current weather-climate situation, and may go into Stage 1 during the next 1-3 weeks. Again, forecast uncertainty is about as high as it can get.
As we progress into the upcoming boreal winter, to me it will be interesting to watch how far east the above discussed SST anomaly pattern progresses. I do think there will continue to be 2 regions of tropical forcing (on average). We may also observe a fair frequency of GSDM Stages 4-1 as opposed to a persistent GSDM Stage 2-3 during January-February. Whatever the case, while a “simple” seasonal mean (DJF, for example) pattern of temperature and precipitation anomalies may emerge which many might attribute to warm ENSO, the variability may be anything but simple with a great deal of global high impact weather with contributions coming from other complex processes not well understood (which is one reason why no 2 warm and cold events are alike beyond the composite/statistical senses).
To summarize, I think we have 1) a warm event (plus a global warming signal, with cause still unclear(?)), 2) an increasing role of the Indian Ocean SSTs, 3) the possibility of a re-emerging MJO signal, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, 6) increasing blocking at the higher latitudes which I can link to both regions of tropical forcing and 7) the always present seasonal cycle issues.
Amplification is occurring throughout much of the subtropics and extratropics from Asia-North America as I type. A residual of the once extended strong North Pacific jet (anomalies are ~30-40m/s ~40N east of the date line at 250mb) is likely to penetrate into much of the country during week 1. The models do show this; however, it is still unclear where and when any amplifying trough will occur. There is likely to be high impact weather for at least the Pacific Northwest (heavy rain) and Deep South/Ohio Valley (severe local storms, etc.) , and perhaps the Upper Mississippi Valley and Great Lakes for winter weather. Disciplined monitoring will be needed including the models as they “catch on”.
During weeks 2-3 a more “classic” GSDM Stage 1 (with subtropical jets) may be probable particularly if at least a “MJO-like” feature develops. That would be favorable for full-latitude troughs to penetrate into western North America having an Arctic cold air source. We should all know “what that means” by now.
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~date line-South America with cool readings around Indonesia particularly south of the equator (see November 3rd posting for details). The warmest SSTs are still found along the equatorial date line with readings near 31C having ~2C anomalies. Equatorial SST and SST anomaly tendencies over the last week were ~minus 0.5-1.0C from around 140E-South America with some positive values across the Indian Ocean. Additionally, SST animations suggest there has been about a 10 degree eastward shift of the warm-cool-warm pattern discussed above during the last 2-3 months (seasonal cycle understood).
What is also interesting is the above average SSTs across the extratropical North Pacific Ocean basin. Granted, the latter have a secondary role to tropical SSTs (and different ocean-atmosphere dynamical processes – I need to keep down the length!). However, warm North Pacific SSTs is not consistent with a warm ENSO (in the composite sense), again keeping in mind the seasonal cycle. The latter could quickly change should GSDM Stage 3 evolve meaning a strong North Pacific jet with attendant East Asian cold air surges, etc., (which does not look probable for at least the next few weeks).
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
The point I want to emphasize in this writing is our two regions of tropical convective forcing is back. One region extends from equatorial Africa into the central Indian Ocean with the other centered ~0/160E. Yes, there are those who will invoke the Indian Ocean Dipole (IOD) notions and offer this situation is not all that unusual for a warm ENSO. While there is truth to these concepts, from my monitoring of trying to understand the dynamics of ocean-atmosphere forcing-response-feedbacks involving many scales of motion making use of the GSDM framework, the current weather-climate situation is much more complicated. From looking at animations of daily mean 150mb and 250mb vector wind anomalies I can clearly see the extratropics interacting with both regions of tropical forcing while helping to maintain them. We need to also remember this current warm ENSO evolved in a very random (and unpredictable) manner.
There is evidence from various tools (ex., Hovmoller plots of 250mb meridional wind anomalies in the 10-40N/S latitude bands) that subtropical wave trains are currently present in both hemispheres. I also have a suspicion that the tropical forcing over Africa into the Indian Ocean is trying to evolve into another MJO (the Wheeler phase space plot supports this). We will see. Global relative AAM tendency as of November 6th was ~minus 20 Hadleys as zonal mean westerly wind anomalies propagate poleward to ~30N/S while being replaced by zonal mean easterly wind anomalies throughout the deep tropics (magnitudes ~5-15m/s at 200mb). GSDM Stage 4 still best describes our current weather-climate situation, and may go into Stage 1 during the next 1-3 weeks. Again, forecast uncertainty is about as high as it can get.
As we progress into the upcoming boreal winter, to me it will be interesting to watch how far east the above discussed SST anomaly pattern progresses. I do think there will continue to be 2 regions of tropical forcing (on average). We may also observe a fair frequency of GSDM Stages 4-1 as opposed to a persistent GSDM Stage 2-3 during January-February. Whatever the case, while a “simple” seasonal mean (DJF, for example) pattern of temperature and precipitation anomalies may emerge which many might attribute to warm ENSO, the variability may be anything but simple with a great deal of global high impact weather with contributions coming from other complex processes not well understood (which is one reason why no 2 warm and cold events are alike beyond the composite/statistical senses).
To summarize, I think we have 1) a warm event (plus a global warming signal, with cause still unclear(?)), 2) an increasing role of the Indian Ocean SSTs, 3) the possibility of a re-emerging MJO signal, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, 6) increasing blocking at the higher latitudes which I can link to both regions of tropical forcing and 7) the always present seasonal cycle issues.
Amplification is occurring throughout much of the subtropics and extratropics from Asia-North America as I type. A residual of the once extended strong North Pacific jet (anomalies are ~30-40m/s ~40N east of the date line at 250mb) is likely to penetrate into much of the country during week 1. The models do show this; however, it is still unclear where and when any amplifying trough will occur. There is likely to be high impact weather for at least the Pacific Northwest (heavy rain) and Deep South/Ohio Valley (severe local storms, etc.) , and perhaps the Upper Mississippi Valley and Great Lakes for winter weather. Disciplined monitoring will be needed including the models as they “catch on”.
During weeks 2-3 a more “classic” GSDM Stage 1 (with subtropical jets) may be probable particularly if at least a “MJO-like” feature develops. That would be favorable for full-latitude troughs to penetrate into western North America having an Arctic cold air source. We should all know “what that means” by now.
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our recently accepted paper by MWR which discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM. Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
Saturday, November 04, 2006
SST Axis of Evil Continues
Please see past postings for web site links. I am going to discontinue inserting most of them in an effort for brevity. I also need to do the same with these postings.
The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~170E-South America with cool readings around Indonesia particularly south of the equator. There has been some warming of SSTs around Indonesia into the Bay of Bengal and Arabian Sea extending to just southeast of Asia, as well as northwest of Australia, with positive tendencies ~0.5-1.0C during the past week. The latter may be a direct result of solar input due to the strong convective suppression present there.
SST anomaly magnitudes as low as ~minus 2C remain just south of Indonesia on 3 November while ~plus 2C were observed just east of the equatorial date line and west of South America (keep in mind the seasonal cycle of SSTs). These positive SST anomalies are deep with plus 4C and greater observed at ~150m/165W per five-day averaged TAO buoy data ending 3 November. A recent surface westerly wind burst linked to the last MJO event appears to have initiated a down welling oceanic Kelvin wave currently approaching 160W along the equator.
The SST horse shoe pattern of cool surrounding warm anomalies (would be reversed for a cold event) across the tropical Indo-Pacific remains (axes of SST anomalies), and is best defined across the Southern Hemisphere with values ~minus 1-2C. Interestingly, there is anomalous SST warmth emanating from the Indian Ocean encasing the cool anomalies across both hemispheres including the extratropics.
Overall, the spatial coverage of above average global SSTs (tropics and extratropics) exceeds those which are cooler than normal. Much of the midlatitude South Pacific Ocean has below normal SSTs as a response to cooling from an intense baroclinic storm track since at least May 2006. It is my feeling that anomalous surface cross equatorial cool southerly flow from the deep southern extratropics into Indonesia starting around May 2006 linked to this storm track activity played a critical role to the evolution of our stochastically forced warm event. Please remember that in the tropics the SSTs generally force the atmosphere with the opposite for the extratropics (yes, everything understood).
SSTs of 30C and warmer cover much of the equatorial date line region while ~29-29.5C waters are present across the central Indian Ocean and around both sides of Central America. Weak positive SST anomalies cover most of the tropical Atlantic with actual temperatures ~28-29C. The warm ENSO conditions are here to stay for at least the next 3-6 months. It is now a matter of how the spatial patterns of the SSTs evolve, and no two warm events (or anything else that occurs in the coupled global ocean-atmosphere, etc. system) are alike. The predictability of these kinds of details on the seasonal time scale is noise, as are the weather impacts.
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
The dynamical signal with the MJO is all but gone. Per full disk satellite imagery and other tools enhanced tropical convective forcing remains most intense around 0/160E (OLRA~ minus 90W/m**2), with two other regions from Africa into the central Indian Ocean and the last from the Amazons and SACZ into the Atlantic ITCZ. The convection across the west central Pacific has been shifting west during the last week, weakly projecting onto a convectively coupled Rossby mode. Some consolidation of forcing is possible during the next couple of weeks north of Indonesia, and particular attention will need to be paid from the Bay of Bengal to the Philippines should this occur.
In general, as has been true since ~2002, it appears probable that we may have to deal with 2 regions of tropical convective forcing (and a weak, if any, MJO signal) again for this upcoming boreal winter, with the warm ENSO signal possibly dominating. I would expect to see coherent tropical convective forcing evolve and propagate east, but perhaps much faster than MJOs (Kelvin waves), and maybe other “MJO-like” behaviors (see our weather-climate discussions). Is the latter the result of a longer term trend such as global warming (what I termed as a “new world atmosphere” in past postings)?
Since about Halloween, tied to the past MJO, there has been fairly coherent poleward propagation of zonal mean zonal westerly wind anomalies with magnitudes up to 15m/s ~35N at 200mb during the past couple of days. Zonal mean upper tropospheric easterly wind anomalies have become dominate within 10 degrees of the equator during the past week (and also from ~45-60N). Global relative AAM has become slightly negative (~minus .5 sigma per operational data), with much of that coming from the global mountain torque of ~minus 15 Hadleys. I can attribute some of this as the result of anomalously low mean sea level pressures along the east slopes of north-south mountain ranges for both the tropics and extratropics impacted by the poleward propagation of the zonal mean anomalous westerlies discussed above. The reason is not only have these westerlies been propagating poleward, but also downward through the troposphere, eventually reaching the surface. There have also been complex interactions with much faster time scales such as the mid-latitude eddies that have subsequently impacted the tropical convection (which has also contributed to recent lowering of mean sea level pressures across the deep tropics).
In terms of the tropical forcing and AAM budget, GSDM Stage 4 may best describe the current situation. However, as shown by the ESRL/PSD animations of both 150mb and 250mb daily mean vector wind anomalies, with magnitudes of roughly 15-30m/s, twin tropical/subtropical cyclones cover much of the Indian Ocean while anticyclones rule over the central Pacific centered around the date line. Centered ~40N, a large anomalous cyclonic gyre covers much of the North Pacific Ocean basin supporting enhanced westerlies ~30-35N (consistent with the poleward propagation discussed above). In fact, a weekly average of 150mb vector wind anomalies ending 4 November suggests a coherent residual of Rossby wave energy dispersion linked to the west central Pacific tropical forcing arcing to a blocking pattern across the North Atlantic (which would project onto a reverse NAO and explain some of the current zonal mean anomalous higher latitude easterly flow). Thus in terms of the actual global circulation GSDM Stage 3 may apply (suggesting split flow across North America).
This kind of response can be expected from a warm ENSO, and may be a pre-cursor to the type of circulation pattern for this upcoming boreal winter. For the USA, during the past week we have seen precipitation increase along the west coast from northern California to Alberta (yes, Canada) while much of the rest of the country has turned warmer and dryer. Back to the GSDM, I would offer Stages 3-4 for the current situation.
To summarize, I think we have 1) a warm event (plus a global warming signal whose cause is unclear?), 2) an increasing role of the Indian Ocean SSTs, 3) the MJO signal which has become very weak, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, and 6) seasonal cycle issues.
As stated above, we may be seeing an early November rendition of an expanded East Asian Jet (EAJ). There are countless sensitivity issues discussed in past postings and weather-climate discussions. I also did not discuss how our GSDM Stage 3 (like?) circulation may have come about over the past week due to complexity. Short story is that in addition to the tropical forcing discussed above, tied to East Asian baroclinic wave packets, there was also a flare-up if convection around the Philippines (Tropical Northwest Pacific) that led to former Super Typhoon Cimarron. This forcing also added westerly flow. With that convection “gone” and at least some consolidation (see above) by around week 2, I think the North Pacific Jet will retract. This is just one of the sensitivity matters the current numerical models are struggling with in terms of predictions.
During this upcoming week, a split flow pattern should remain across the country. Most of the precipitation looks to occur along the west coast (mainly Pacific Northwest) and eventually across the Deep South. The latter will depend on just how much baroclinic development occurs along the southern westerlies. Whatever the case may be, a cold air source looks to be lacking.
For weeks 2-3, GSDM Stage 1 may evolve, meaning a full latitude trough with an Arctic cold air source (monitoring does show some recent build up – recall where the blocks are) would become increasingly probable for the western half of the country. There may also be an active subtropical jet tied to the warm ENSO. This would be a very active weather regime (including possible high-impact events such as blizzard conditions and severe local storms) for this time of year across a good part of the country (including a southwest flow storm track across the middle). I think the readers are familiar what the weather would be from all this.
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our MWR paper that discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM.
Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
The spatial distribution of global tropical SST anomalies has not changed significantly during the past week or so, still resembling a mature warm event. Positive anomalies remain across the western Indian Ocean and along the equator from ~170E-South America with cool readings around Indonesia particularly south of the equator. There has been some warming of SSTs around Indonesia into the Bay of Bengal and Arabian Sea extending to just southeast of Asia, as well as northwest of Australia, with positive tendencies ~0.5-1.0C during the past week. The latter may be a direct result of solar input due to the strong convective suppression present there.
SST anomaly magnitudes as low as ~minus 2C remain just south of Indonesia on 3 November while ~plus 2C were observed just east of the equatorial date line and west of South America (keep in mind the seasonal cycle of SSTs). These positive SST anomalies are deep with plus 4C and greater observed at ~150m/165W per five-day averaged TAO buoy data ending 3 November. A recent surface westerly wind burst linked to the last MJO event appears to have initiated a down welling oceanic Kelvin wave currently approaching 160W along the equator.
The SST horse shoe pattern of cool surrounding warm anomalies (would be reversed for a cold event) across the tropical Indo-Pacific remains (axes of SST anomalies), and is best defined across the Southern Hemisphere with values ~minus 1-2C. Interestingly, there is anomalous SST warmth emanating from the Indian Ocean encasing the cool anomalies across both hemispheres including the extratropics.
Overall, the spatial coverage of above average global SSTs (tropics and extratropics) exceeds those which are cooler than normal. Much of the midlatitude South Pacific Ocean has below normal SSTs as a response to cooling from an intense baroclinic storm track since at least May 2006. It is my feeling that anomalous surface cross equatorial cool southerly flow from the deep southern extratropics into Indonesia starting around May 2006 linked to this storm track activity played a critical role to the evolution of our stochastically forced warm event. Please remember that in the tropics the SSTs generally force the atmosphere with the opposite for the extratropics (yes, everything understood).
SSTs of 30C and warmer cover much of the equatorial date line region while ~29-29.5C waters are present across the central Indian Ocean and around both sides of Central America. Weak positive SST anomalies cover most of the tropical Atlantic with actual temperatures ~28-29C. The warm ENSO conditions are here to stay for at least the next 3-6 months. It is now a matter of how the spatial patterns of the SSTs evolve, and no two warm events (or anything else that occurs in the coupled global ocean-atmosphere, etc. system) are alike. The predictability of these kinds of details on the seasonal time scale is noise, as are the weather impacts.
The following are links to ENSO discussions.
http://www.cdc.noaa.gov/people/klaus.wolter/MEI
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html
Please also see the following CPC link (and others therein) for further ENSO, etc., insights, and remember that official USA information on anything related to ENSO comes from CPC.
http://www.cpc.ncep.noaa.gov/products/predictions/90day/
The dynamical signal with the MJO is all but gone. Per full disk satellite imagery and other tools enhanced tropical convective forcing remains most intense around 0/160E (OLRA~ minus 90W/m**2), with two other regions from Africa into the central Indian Ocean and the last from the Amazons and SACZ into the Atlantic ITCZ. The convection across the west central Pacific has been shifting west during the last week, weakly projecting onto a convectively coupled Rossby mode. Some consolidation of forcing is possible during the next couple of weeks north of Indonesia, and particular attention will need to be paid from the Bay of Bengal to the Philippines should this occur.
In general, as has been true since ~2002, it appears probable that we may have to deal with 2 regions of tropical convective forcing (and a weak, if any, MJO signal) again for this upcoming boreal winter, with the warm ENSO signal possibly dominating. I would expect to see coherent tropical convective forcing evolve and propagate east, but perhaps much faster than MJOs (Kelvin waves), and maybe other “MJO-like” behaviors (see our weather-climate discussions). Is the latter the result of a longer term trend such as global warming (what I termed as a “new world atmosphere” in past postings)?
Since about Halloween, tied to the past MJO, there has been fairly coherent poleward propagation of zonal mean zonal westerly wind anomalies with magnitudes up to 15m/s ~35N at 200mb during the past couple of days. Zonal mean upper tropospheric easterly wind anomalies have become dominate within 10 degrees of the equator during the past week (and also from ~45-60N). Global relative AAM has become slightly negative (~minus .5 sigma per operational data), with much of that coming from the global mountain torque of ~minus 15 Hadleys. I can attribute some of this as the result of anomalously low mean sea level pressures along the east slopes of north-south mountain ranges for both the tropics and extratropics impacted by the poleward propagation of the zonal mean anomalous westerlies discussed above. The reason is not only have these westerlies been propagating poleward, but also downward through the troposphere, eventually reaching the surface. There have also been complex interactions with much faster time scales such as the mid-latitude eddies that have subsequently impacted the tropical convection (which has also contributed to recent lowering of mean sea level pressures across the deep tropics).
In terms of the tropical forcing and AAM budget, GSDM Stage 4 may best describe the current situation. However, as shown by the ESRL/PSD animations of both 150mb and 250mb daily mean vector wind anomalies, with magnitudes of roughly 15-30m/s, twin tropical/subtropical cyclones cover much of the Indian Ocean while anticyclones rule over the central Pacific centered around the date line. Centered ~40N, a large anomalous cyclonic gyre covers much of the North Pacific Ocean basin supporting enhanced westerlies ~30-35N (consistent with the poleward propagation discussed above). In fact, a weekly average of 150mb vector wind anomalies ending 4 November suggests a coherent residual of Rossby wave energy dispersion linked to the west central Pacific tropical forcing arcing to a blocking pattern across the North Atlantic (which would project onto a reverse NAO and explain some of the current zonal mean anomalous higher latitude easterly flow). Thus in terms of the actual global circulation GSDM Stage 3 may apply (suggesting split flow across North America).
This kind of response can be expected from a warm ENSO, and may be a pre-cursor to the type of circulation pattern for this upcoming boreal winter. For the USA, during the past week we have seen precipitation increase along the west coast from northern California to Alberta (yes, Canada) while much of the rest of the country has turned warmer and dryer. Back to the GSDM, I would offer Stages 3-4 for the current situation.
To summarize, I think we have 1) a warm event (plus a global warming signal whose cause is unclear?), 2) an increasing role of the Indian Ocean SSTs, 3) the MJO signal which has become very weak, 4) 20-30 day tropical convective variability (not discussed), 5) some evidence of mountain-frictional torque index cycle variations (also not discussed – may be linked to (4)), fast RWDs, baroclinic wave packets and all sorts of other white noise, and 6) seasonal cycle issues.
As stated above, we may be seeing an early November rendition of an expanded East Asian Jet (EAJ). There are countless sensitivity issues discussed in past postings and weather-climate discussions. I also did not discuss how our GSDM Stage 3 (like?) circulation may have come about over the past week due to complexity. Short story is that in addition to the tropical forcing discussed above, tied to East Asian baroclinic wave packets, there was also a flare-up if convection around the Philippines (Tropical Northwest Pacific) that led to former Super Typhoon Cimarron. This forcing also added westerly flow. With that convection “gone” and at least some consolidation (see above) by around week 2, I think the North Pacific Jet will retract. This is just one of the sensitivity matters the current numerical models are struggling with in terms of predictions.
During this upcoming week, a split flow pattern should remain across the country. Most of the precipitation looks to occur along the west coast (mainly Pacific Northwest) and eventually across the Deep South. The latter will depend on just how much baroclinic development occurs along the southern westerlies. Whatever the case may be, a cold air source looks to be lacking.
For weeks 2-3, GSDM Stage 1 may evolve, meaning a full latitude trough with an Arctic cold air source (monitoring does show some recent build up – recall where the blocks are) would become increasingly probable for the western half of the country. There may also be an active subtropical jet tied to the warm ENSO. This would be a very active weather regime (including possible high-impact events such as blizzard conditions and severe local storms) for this time of year across a good part of the country (including a southwest flow storm track across the middle). I think the readers are familiar what the weather would be from all this.
Work is on-going to write another weather-climate discussion for the ESRL/PSD MJO web page. Since it would be ideal to have this discussion posted before attending the 4-8 December 2006 THORPEX meeting in Germany, it will be difficult for me to do these postings weekly. Please keep checking, and see the Appendix.
Appendix
The following is a link to our MWR paper that discusses the GSDM (Weickmann and Berry 2006, in press).
http://www.cdc.noaa.gov/MJO/Predictions/wb2006.pdf
From taking into consideration the interactions of 4 different subseasonal time scales, a sequence of maps depicting a coherent set of repeatable events has been derived for the Northern Hemisphere cold season from November-March. This set is broken up into 4 stages, referred to as GSDM (for Global Synoptic-Dynamic Model) Stages 1-4 in the text of my Blog. Figure 13 in our paper presents a schematic of the GSDM. Ideally it would be advantageous to post our weather-climate discussions with greater frequency to provide additional detail while having a more complete weather-climate record of attribution and prediction. In these discussions I adapt the GSDM for the warm season. Our list of work includes a seasonally adjusted rendition of the GSDM.
Our latest weather-climate discussion dated August 18th, 2006 (and updated September 9th), has been posted on the ESRL/PSD MJO web site at
http://www.cdc.noaa.gov/MJO/Forecasts/climate_discussions.html
Ed Berry
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