Global tropical SSTs still remain above average, with the greatest anomalies across the Indo-Pacific region especially from the central equatorial Pacific to the west coast of South America. Magnitudes across the latter are ~plus 1-3C and extend to ~125m deep (up to 5C) per latest TAO buoy data. It appears that the oceanic Kelvin wave initiated around October 1st is about to reach the South American coast.
The warm-cool-warm SST distribution observed for the past several months has nearly disappeared suggesting our warm event may have already peaked (at least for this cold season). In any case, actual SSTs 29C (threshold for supporting sustained tropical convection) and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.
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/
Since my last posting about a week ago, the most important development in the global weather-climate system has been the evolution of a coherent eastward propagating convectively coupled mode from the Indian Ocean into Indonesia. Per full disk satellite imagery the centroid of this feature was ~0/110E, and was clearly detached from lingering convection across the western Indian Ocean and South Africa (tropical cyclones understood). Interestingly portions of Indonesia that have been convectively suppressed for the last several months are finally getting enhanced rainfall. The Wheeler phase space plot and other tools suggest a strong projection onto a MJO for this eastward moving coupled tropical convective system. My own loose calculations have this MJO moving east ~6-7m/s (5 deg long/day), having speed up a bit during the last few days. I have a concern this MJO may shift into the west central Pacific faster than typically observed.
Forcing from the extratropics has led to yet another separate flare-up ~150-160E over the warm SSTs while the western hemisphere is dynamically suppressed. I do think this MJO will shift into the west central Pacific (while also drifting southward – most numerical and statistical tools agree), possibly consolidating with SST boundary forced convection farther to the east. I suspect we will also see the onset of the Australian monsoon as well as other seasonal cycle behaviors during the next 1-2 weeks. At some point (weeks 3-4?) enhanced convection would be expected to become quite strong around the equatorial date line and South Pacific as the MJO enhances the warm ENSO signal.
The global circulation has responded accordingly including anomalous twin upper tropospheric (baroclinic structures) Indian Ocean anticyclones and down stream west Pacific cyclones. Zonal mean anomalous easterly flow continues across the global tropical atmosphere and global relative AAM is slightly below normal (reanalysis climatology). However, equatorial upper tropospheric westerly wind anomalies (~5-15m/s) are starting to appear over the central and east Pacific. I think we are evolving from GSDM Stage 4 to 1. Complicating things have been the ~15 day central Pacific tropical convective flare-ups and rapid processes across the northern extratropics involving the east-Asian topography (mountain torque term of the global AAM budget).
As the MJO shifts into the west Pacific and eventually enhances the warm ENSO signal, subtropical westerly flow should increase (this process may already be starting per above). Also, as this tropical forcing excites Rossby wave trains which subsequently interact with extratropical baroclinic wave packets, I would expect anticyclonic circulation anomalies to begin dominating the northern polar latitudes and possibly lead to a warming of the stratosphere. In fact, per animations of 150mb daily mean vector wind anomalies, there have already been “bursting anticyclones” across the northern high latitudes for at least the past 1-2 weeks (and stratospheric temperatures have been rising). This would lead to negative phases of things like the AO.
As more models are showing, an evolution from GSDM Stage 1-2 is probable during the next 1-3 weeks. This means after week 1, ridge amplification around 140W into Alaska (linking up with a SSW signal?) may occur during week 2 with a downstream trough in the Rockies (~110W). This pattern would be expected to shift ~10 degrees to the east during week 3. At this time surface temperature anomalies of at least minus 10C are present across much of Alaska, and all that may eventually be forced southward into the western USA. Thus a cold and wet regime for much of the Rockies and Plains may be probable weeks 2-3 which may allow a good snow pack to build across large portions of the country. Afterwards (late January into February), a combined extended anomalously strong North Pacific jet ~30-35N leading to split flow across North America typical of a warm ENSO may be most probable (GSDM Stage 3). That would increase the risk of high impact precipitation events for the USA west coast, particularly California.
Finally, I offer a few comments. The intense tropical convective forcing that we have been observing across the Indian Ocean for the past several months is not typical of a warm ENSO (especially when it dominates over and suppresses the central Pacific). Also, there has been this issue of 2 regions of tropical convective forcing (Indian Ocean and west of date line) since early 2002. I think there a global warming signal (cause is unclear) being communicated to the atmosphere through the anomalously warm tropical SSTs. We have also been seeing lots of forcing-response-feedback scenarios involving the global oceans and atmosphere for the past several years which have been difficult to understand let alone predict. The point is there have been more GSDM “Stage 4-like” responses observed, and I suspect going into the February-April 2007 period we may see more occurrences Stages "4-1" global circulation behaviors.
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
Also, our latest weather-climate discussion was posted on November 29th at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability.
I hope to get an update out by late next week. As stated previously, while I am at ESRL/PSD (starting 1/8/07) we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see
http://www.esrl.noaa.gov/psd/programs/2007/hmt/).
Ed Berry
Friday, December 29, 2006
Tuesday, December 19, 2006
A Circulation Response Looms
Global tropical SSTs generally remain above average, with the greatest anomalies across the Indo-Pacific region especially from the central equatorial Pacific to the west coast of South America. Magnitudes across the latter are ~plus 1-3C and extend to 125m deep (up to 5C) per latest TAO buoy data as part of the warm ENSO signal. Interestingly, deep cool anomalies ~1-2C are appearing west of the date line and the 20C isotherm depth has shoaled to about 150W. The warm-cool-warm SST distribution observed for the past several months has become less distinct suggesting our warm event may have already peaked. In any case, actual SSTs 29C (threshold for supporting sustained tropical convection) and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.
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/
Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) a relatively fast dynamical signal (~15-20m/s) that was moving east through the Western Hemisphere has emerged into Africa and the Indian Ocean. An intense region of deep convection (3-day OLRA less than minus 70W/m**2) has resulted across the equatorial Indian Ocean centered ~70E (including TC Bondo across the South Indian Ocean) and is projecting onto a MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another burst of convection to persist ~0/160E while diurnal activity still continues across the Amazons of northern South America.
To sum up, we continue to see two primary regions of active forcing, Indian Ocean and west of the date line (suppression in between), being modulated by at least MJO-like variations, Kelvin waves and flare-ups with time scales varying anywhere from 5-35 days. The pattern of the 2 regions of active forcing has loosely been drifting east since October (~ 30deg), particularly the Indian Ocean enhancement-Indonesian suppression portion. The Indian Ocean has tended to dominate the central Pacific forcing, and all of these kinds of behaviors are not consistent with the composite tropical convective response to a developing warm ENSO.
A response to the multiple regions of tropical forcing has been for zonal mean easterly wind anomalies to increase throughout much of the equatorial atmosphere since roughly the start of this month (magnitudes approaching 10m/s at 200mb starting about December 13th). Anomalous twin upper tropospheric anticyclones located around 60E, 180 and 60W (per 150mb 12/19/06 daily mean vector wind anomalies) are supporting these easterlies and are also part of the tropical-extratropical circulation response. These easterlies are beginning to propagate poleward off the equator while zonal mean westerly wind anomalies remain across the subtropical and midlatitude atmospheres. Based on the ESRL/PSD reanalysis data AAM plots, as of December 16th the global tendency had reached about minus 15 Hadleys with contributions not only from the equatorial zonal mean easterlies but also weakly from the global mountain and frictional torques (see plots for details). I think GSDM Stage 4 best describes the current weather-climate situation.
My thoughts remain that sometime during weeks 2-3, going along with the seasonal cycle, a consolidation of the tropical forcing may occur centered ~150-160E as it shifts south. Heading into the first week of January we may see a large region of strong tropical thunderstorm activity extend from the South Pacific to just east of Indonesia. This may maintain an increased risk for tropical cyclones across the South Indian Ocean as well as the South Pacific to the east coast of Australia. Afterwards, this whole region may shift southeast along the SPCZ while the ITCZ and much of Brasil are active. I would also expect to the Indian Ocean and Indonesia to remain periodically active. In fact, at some point, say February-March, much of the East Indian Ocean and Indonesia may become quite active while the central Pacific starts to shut down. What is left of the dynamical warm ENSO signal may be centered near the Americas.
I think we are transitioning to GSDM Stage 1 as I type. Uncertainty for any predictive insight remains extremely high. However, after Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a GSDM Stage 2 situation did not evolve. That would suggest ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. The Pacific Northwest may still see bouts of precipitation as the troughs come inland. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO. At that point the precipitation emphasis would be along the USA west coast as well as the Deep South. While the latter may verify for a January-March seasonal mean, I could see the February-March period going back to GSDM Stages 4-1.
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
Also, our latest weather-climate discussion was posted on November 29th at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability. I hope to get an update out by late next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see
http://www.esrl.noaa.gov/psd/programs/2007/hmt/).
Ed Berry
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/
Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) a relatively fast dynamical signal (~15-20m/s) that was moving east through the Western Hemisphere has emerged into Africa and the Indian Ocean. An intense region of deep convection (3-day OLRA less than minus 70W/m**2) has resulted across the equatorial Indian Ocean centered ~70E (including TC Bondo across the South Indian Ocean) and is projecting onto a MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another burst of convection to persist ~0/160E while diurnal activity still continues across the Amazons of northern South America.
To sum up, we continue to see two primary regions of active forcing, Indian Ocean and west of the date line (suppression in between), being modulated by at least MJO-like variations, Kelvin waves and flare-ups with time scales varying anywhere from 5-35 days. The pattern of the 2 regions of active forcing has loosely been drifting east since October (~ 30deg), particularly the Indian Ocean enhancement-Indonesian suppression portion. The Indian Ocean has tended to dominate the central Pacific forcing, and all of these kinds of behaviors are not consistent with the composite tropical convective response to a developing warm ENSO.
A response to the multiple regions of tropical forcing has been for zonal mean easterly wind anomalies to increase throughout much of the equatorial atmosphere since roughly the start of this month (magnitudes approaching 10m/s at 200mb starting about December 13th). Anomalous twin upper tropospheric anticyclones located around 60E, 180 and 60W (per 150mb 12/19/06 daily mean vector wind anomalies) are supporting these easterlies and are also part of the tropical-extratropical circulation response. These easterlies are beginning to propagate poleward off the equator while zonal mean westerly wind anomalies remain across the subtropical and midlatitude atmospheres. Based on the ESRL/PSD reanalysis data AAM plots, as of December 16th the global tendency had reached about minus 15 Hadleys with contributions not only from the equatorial zonal mean easterlies but also weakly from the global mountain and frictional torques (see plots for details). I think GSDM Stage 4 best describes the current weather-climate situation.
My thoughts remain that sometime during weeks 2-3, going along with the seasonal cycle, a consolidation of the tropical forcing may occur centered ~150-160E as it shifts south. Heading into the first week of January we may see a large region of strong tropical thunderstorm activity extend from the South Pacific to just east of Indonesia. This may maintain an increased risk for tropical cyclones across the South Indian Ocean as well as the South Pacific to the east coast of Australia. Afterwards, this whole region may shift southeast along the SPCZ while the ITCZ and much of Brasil are active. I would also expect to the Indian Ocean and Indonesia to remain periodically active. In fact, at some point, say February-March, much of the East Indian Ocean and Indonesia may become quite active while the central Pacific starts to shut down. What is left of the dynamical warm ENSO signal may be centered near the Americas.
I think we are transitioning to GSDM Stage 1 as I type. Uncertainty for any predictive insight remains extremely high. However, after Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a GSDM Stage 2 situation did not evolve. That would suggest ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. The Pacific Northwest may still see bouts of precipitation as the troughs come inland. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO. At that point the precipitation emphasis would be along the USA west coast as well as the Deep South. While the latter may verify for a January-March seasonal mean, I could see the February-March period going back to GSDM Stages 4-1.
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
Also, our latest weather-climate discussion was posted on November 29th at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability. I hope to get an update out by late next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see
http://www.esrl.noaa.gov/psd/programs/2007/hmt/).
Ed Berry
Friday, December 15, 2006
Only a Matter of Time? Will There be Winter?
Global tropical SSTs generally remain above average. The greatest anomalies are across the Indo-Pacific region with magnitudes ~plus 1-3C especially along the equatorial cold tongue. The latter is associated with the basin wide warm ENSO, with the warm anomalies (up to 5C) extending to 150m deep per latest TAO buoy data. Interestingly, deep cool anomalies ~1-2C are appearing west of the date line and the 20C isotherm depth has shoaled to about 160W. Also, the warm-cool-warm SST distribution has become less distinct during the past several weeks. Perhaps our warm event may have already peaked. In any case, actual SSTs 29C and higher extend from the South Pacific into eastern Indonesia and over portions of the Indian Ocean.
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/
Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) relatively fast dynamical signals moving through the Western Hemisphere are starting to emerge into Africa and the Indian Ocean. A fairly intense flare-up has occurred ~0/60E during the last week and may be evolving into a weak MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another intense burst of convection to occur ~0/160E while intense diurnal activity persists across the Amazons of northern South America. At least 2 and arguably 3 significant regions (counting South America) of tropical forcing are impacting the extratropics. In fact, extratropical responses and feedbacks linked to some of this activity may have contributed to recent very poor week-2 500mb ACC skill scores for the NCEP GFS ensemble mean for North America (less than minus 0.3). Since early October the enhanced-suppressed-enhanced distribution of tropical forcing across the Indo-Pacific region has shifted roughly 40 degrees to the east, which may reflect a slow ENSO signal.
Zonal mean easterly wind anomalies have been increasing throughout the equatorial and particularly northern subtropical atmospheres since about the start of this month (~5-10m/s at 200mb). Anomalous zonal mean westerly flow flanks these easterlies suggestive of subtropical jets across both hemispheres. GSDM Stage 4 best describes the current weather climate situation (not all AAM plots from ESRL/PSD are available). Where we go from here remains very unclear. As I have offered before, my thoughts are to expect some consolidation of the tropical forcing from the west central into the South Pacific going into January 2007 (as it shifts south).
Nearly all the numerical models are suggesting closed low development across the Desert Southwest by early next week to then eject northeast affecting much of the country. Thus while winter storm conditions are probable from the central Rockies into the portions of the Plains, the Deep South may receive heavy rainfall along with severe local storms. True Arctic air will be lacking with this system.
After Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a robust GSDM Stage 2 situation did not evolve (bypassing Stage 1). That would mean ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO.
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
Also, our latest weather-climate discussion was posted on November 29th at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability.
I will try to do at least a short posting next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see
http://www.esrl.noaa.gov/psd/programs/2007/hmt/).
Ed Berry
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/
Tropical convective forcing remains very complicated. Per full disk satellite imagery and monitoring tools (such as coherent modes and velocity potential Hovmollers) relatively fast dynamical signals moving through the Western Hemisphere are starting to emerge into Africa and the Indian Ocean. A fairly intense flare-up has occurred ~0/60E during the last week and may be evolving into a weak MJO per Wheeler phase plot. SST boundary forcing and Southern Hemisphere frontal activity has allowed another intense burst of convection to occur ~0/160E while intense diurnal activity persists across the Amazons of northern South America. At least 2 and arguably 3 significant regions (counting South America) of tropical forcing are impacting the extratropics. In fact, extratropical responses and feedbacks linked to some of this activity may have contributed to recent very poor week-2 500mb ACC skill scores for the NCEP GFS ensemble mean for North America (less than minus 0.3). Since early October the enhanced-suppressed-enhanced distribution of tropical forcing across the Indo-Pacific region has shifted roughly 40 degrees to the east, which may reflect a slow ENSO signal.
Zonal mean easterly wind anomalies have been increasing throughout the equatorial and particularly northern subtropical atmospheres since about the start of this month (~5-10m/s at 200mb). Anomalous zonal mean westerly flow flanks these easterlies suggestive of subtropical jets across both hemispheres. GSDM Stage 4 best describes the current weather climate situation (not all AAM plots from ESRL/PSD are available). Where we go from here remains very unclear. As I have offered before, my thoughts are to expect some consolidation of the tropical forcing from the west central into the South Pacific going into January 2007 (as it shifts south).
Nearly all the numerical models are suggesting closed low development across the Desert Southwest by early next week to then eject northeast affecting much of the country. Thus while winter storm conditions are probable from the central Rockies into the portions of the Plains, the Deep South may receive heavy rainfall along with severe local storms. True Arctic air will be lacking with this system.
After Christmas heading into the first couple of weeks in January 2007, I would almost be surprised if a robust GSDM Stage 2 situation did not evolve (bypassing Stage 1). That would mean ridge amplification just off the North American west coast into Alaska with a few digging synoptic troughs across the Rockies and Plains. Ramifications would include true Arctic air penetrating into the lower 48 states with lots of wintery precipitation to go along with it, especially for the eastern 2/3rds of the country. Afterwards the DREADED extended combined jet from Asia to the west coast of North America (with split flow across the continent) may appear which is typical of GSDM Stage 3 that is most probable during a mature global response to a warm ENSO.
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
Also, our latest weather-climate discussion was posted on November 29th at
http://www.cdc.noaa.gov/people/klaus.weickmann/disc112006/weather_climate_disco_01_December_2006b.html
In the beginning of Section 2 of that report we give a summary description of the Global-Synoptic-Dynamic Model (GSDM) of subseasonal variability.
I will try to do at least a short posting next week. As stated previously, while I am at ESRL/PSD we hope to post at least short writings on this Blog every other day in support of the Hydrometeorological Testbed Project (HMT -- please see
http://www.esrl.noaa.gov/psd/programs/2007/hmt/).
Ed Berry
Subscribe to:
Posts (Atom)