“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. There is little change in the spatial patterns from a week ago. The largest negative global tropical SST anomalies appear to be across the North Atlantic Ocean with magnitudes approaching 3C west of Africa. With varying amplitude, the latter have been persistent for at least the past 2-3 months. Slow warming of the convectively suppressed Indian Ocean continues, with totals approaching 30C.
Nino SSTs are generally near normal. Does this suggest La-Nina is “over”??? When thinking about this, please remember that ENSO is a global phenomenon involving the ocean-land-atmosphere dynamical system. ONI simply does not cut it!
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
As has been the case during much of this past boreal 2008-09 cold season that I will remember as the “La-Nina from Hell”, weather-climate signals are once again conflicting and incredibly complicated. From intense daily monitoring and on-going work to better understand the scientific issues, my comfort level is okay with all this. However, this medium of communication is very inefficient, stressing the importance of brevity. The astute and learned readers will see matters intentionally not discussed.
Not surprisingly, the moist tropical convective forcing with our strong MJO, ~2.5 sigma projection in octant 5 of WH (2004) phase space retaining ENSO, has significantly slowed its eastward propagation. This is consistent with late January and mid-March, the former (latter) after (before) initiation. Full-disk satellite imagery shows the moist convective MJO signal centered ~0/150E extending from near the Philippines into the South Pacific Ocean. Unquestionably and with at least a two-week forecast lead time (see 11 April discussion, for example), this MJO working with extratropical dynamical processes has been impacting the USA. For instance, Rossby wave energy dispersions (RWDs) from the Eastern Hemisphere upper tropospheric anomalous twin anticyclones has contributed to the current digging western USA trough, and there is a subtropical jet across the southern states. A loose superposition of the 250mb snr psi composite anomaly plots for phase 2 of the WB (2009) measure of the GWO and phase 5 for the WH (2004) MJO depicts the ongoing global circulation.
There continues to be little projection in WB (2009) GWO phase space. However, fast time scale processes such as the RWDs discussed above are a component of the GWO. In fact, 250mb circulation wind anomalies have been ~30-50m/s with these features. The weak projection is one ramification of the GWO being a global dynamical circulation measure, and that itself may be a quantification of conflicting weather-climate signals (in this case). However, excursions understood, there has been a clear shift of the GWO along the La-Nina attractor “upward” in phase space. That is, there have been stochastic dynamical processes working to add westerly wind flows to the subtropical atmospheres. This movement has been displaced toward octants 3-5 of GWO phase space, suggestive of a weakening La-Nina.
Updated through 22 April, tropospheric global relative AAM has spiked too slightly above the R1 data climatology. Above normal AAM has not been observed since at least early December 2008. I do think some additional increase is possible in the near term. The punch line is that we are not out of the “bear atmosphere” yet, analogous to the financial markets. Sparing details, there is already subtle evidence our La-Nina base state is attempting to reload. For example, with symmetry anomalous ridges dominate the extratropics of both hemispheres, characteristic of the all too familiar positive phase of the Branstator (2002) circumglobal teleconnection.
Per Wolter (personal communication), La-Nina impacts tend to be less severe during April. Just as stochastic (GWO) forcing gave us the on-going (cheap but strong) MJO which has contributed to the “blessed precipitation” across many previously dry areas across the country, the subtropical westerly wind flow anomalies may be “taken away”. I will be carefully monitoring all aspects of the global and zonal mean terms of the earth-atmosphere AAM budget UFN (components of the GWO). Stay tuned.
In the meantime, during weeks 1 and 2 tropical forcing should become well established across the Western Hemisphere, only to propagate back into what may be a very warm Indian Ocean by roughly weeks 3-4. For simplicity, the superposition of the snr plots discussed above is okay through roughly days 5-7. I think the notion of a 7-8-1-2 transition depicted by both the GWO and MJO 250mb snr psi (and other variables) composite anomaly plots is still the best forecast solution for ~weeks 2-3. During mid-late May the global circulation may be represented by superposition of GWO phases 2-3 with MJO phases 4-5 should Eastern Hemisphere tropical convective forcing intensify.
For the USA, after the week-1 western trough, an extended north Pacific Ocean jet/split flow pattern of western troughs, closed cyclones/downstream southeast states ridge scenario is reasonable ~weeks 2-3 (already offered previously). The latter will be shifting slowly north with the seasonal cycle. Mid-late May heading into June could see a resumption of more full-latitude progressive western and central states troughs, focusing the emphasis for anomalous precipitation and severe local storms across the Northern Plains and Upper Mississippi Valley. Other weather impacts, nationally and internationally, should be understood.
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We are working to mainstream this effort. The support is very much appreciated!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
http://www.wmo.ch/pages/mediacentre/news/index_en.html
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes Rex the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 1-3 May.
Ed Berry
Friday, April 24, 2009
Friday, April 17, 2009
“Stochastic MJO” Hard Times/AAM Rally “for Real???”
“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. Recent intense to severe tropical thunderstorm clusters has led to substantial cooling across much of the Indian Ocean. Anomalies are ~minus 1-2C with totals roughly 28-29.5C. Warmest ocean waters globally are in the region of Indonesia into the west central Pacific having totals around 30C. SST anomalies across the Nino regions are relatively minimal, and the slope of the equatorial Pacific Ocean thermocline is close to normal. Yes, the negative phase of the PDO remains well defined.
While I still think the odds tilt toward at least a weak La-Nina return during the boreal 2009-10 cold season, several very serious weather-climate monitoring issues exist that careful attention must be paid to heading into and during boreal summer. There have already been behaviors involving the weather-climate dynamical system that I would not have expected ~4-6 weeks ago. The latter emphasizes the importance of the role of poorly understood non-linear stochastic forcing.
In yet another likely futile attempt, I want to work to keep these discussions shorter. The time saved can be used for other efforts such as on going work to mainstream weather-climate discussions utilizing the WB (2009) measure of the GWO on the ESRL/PSD GSDM web page. Please leave comments and/or email me if there are questions.
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
The GWO forced MJO continues to progress rapidly eastward (~8-10m/s; Kelvin wave issues understood) through the Eastern Hemisphere, having ~2.5 sigma projection in octant 4 of WH (2004) phase space through 16 April. Full disk satellite imagery and other diagnostic monitoring tools suggest the centroid of this strong MJO signal is ~0-5N/140E. My thought is that while there may be a “slow down period” across roughly the west central Pacific Ocean, the time scale of this MJO is probable to be similar to the late December 2008 into early February event. The latter was roughly 30 days, the fast end of the MJO time scale. Perhaps this is a characteristic of MJOs when stochastic extratropical dynamics are heavily involved with their initiation.
One of those serious monitoring issues I have is that our current MJO will lead to the development of a slower evolving behavior of tropical convective forcing initiating across the Indian Ocean during early May. This may eventually shift east as a MJO and contribute to a significant westerly wind burst across the equatorial west central Pacific during late May/early June. Stay tuned. In any case, the on-going MJO is already impacting the USA (to make that clear), and working with GWO processes, will continue to do so for at least the next several weeks. Only a few of those concerns can be discussed below.
Through 15 April the GWO projection is weak, less than 1 standard deviation in phase space but still tilted toward the La-Nina attractor. Clearly the MJO is dominating any subseasonal signal. However, the dynamical processes represented by the GWO continue to be very important. A research issue on the WB (endless) list of things to do is to more clearly bring out some of those processes. Remember that the WB (2009) measure of the GWO is a global dynamical circulation quantity.
For instance, tied to strong southwest Pacific tropical forcing and midlatitude mountains during the past few weeks, the eddies have worked hard essentially eliminating zonal easterly wind flow anomalies across the Northern Hemisphere subtropical atmosphere. In fact, there are even ~5m/s zonal mean westerly anomalies at 200mb around 25N, and there is an accompanying AAM transports signal. This is why many areas of the USA that had been experiencing severe drought have recently been receiving much needed precipitation.
Speculating, per MJO issues discussed above along with the GWO, maybe this “AAM rally will have legs”. Stay tuned. I continue to find it very interesting what has seemingly been a recent close relationship between the AAM and DJIA time series!
Eastern Hemisphere subtropical transition (first order baroclinic mode) is well underway involving upper tropospheric anomalous twin Indian Ocean (west Pacific) anticyclones (cyclones). Loosely, a superposition of the 250mb psi snr composite anomaly plots for MJO phases 4-5 with GWO 1-3 depict the global circulation. Current Rossby wave energy dispersion (RWD) from the Indian Ocean anticyclones into the North Pacific is one of the signals the models have been catching up to the last few days. That is probable to lead to another western USA trough/eastern states ridge during week-2, a notion offered in my 11 April posting. Afterward, weeks 3-4 may see another GWO/MJO 7-8-1-2 transition suggesting an extension of the East Asian jet across the Pacific collapsing to more strong/energetic split flow western and central states troughs/closed lows. The latter would be during the first part of May, and the storm track is likely to be shifted a bit farther north than recently observed.
Weather ramifications are well understood. For the USA, after a break next week, a resumption of an active storm track pattern focusing on the western and central states appears probable. Precipitation opportunities for many drought regions should continue. Hopefully the Gulf of Mexico will recover from yet another possible late season Tehuantepecker next week.
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 24-26 April.
Ed Berry
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. Recent intense to severe tropical thunderstorm clusters has led to substantial cooling across much of the Indian Ocean. Anomalies are ~minus 1-2C with totals roughly 28-29.5C. Warmest ocean waters globally are in the region of Indonesia into the west central Pacific having totals around 30C. SST anomalies across the Nino regions are relatively minimal, and the slope of the equatorial Pacific Ocean thermocline is close to normal. Yes, the negative phase of the PDO remains well defined.
While I still think the odds tilt toward at least a weak La-Nina return during the boreal 2009-10 cold season, several very serious weather-climate monitoring issues exist that careful attention must be paid to heading into and during boreal summer. There have already been behaviors involving the weather-climate dynamical system that I would not have expected ~4-6 weeks ago. The latter emphasizes the importance of the role of poorly understood non-linear stochastic forcing.
In yet another likely futile attempt, I want to work to keep these discussions shorter. The time saved can be used for other efforts such as on going work to mainstream weather-climate discussions utilizing the WB (2009) measure of the GWO on the ESRL/PSD GSDM web page. Please leave comments and/or email me if there are questions.
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
The GWO forced MJO continues to progress rapidly eastward (~8-10m/s; Kelvin wave issues understood) through the Eastern Hemisphere, having ~2.5 sigma projection in octant 4 of WH (2004) phase space through 16 April. Full disk satellite imagery and other diagnostic monitoring tools suggest the centroid of this strong MJO signal is ~0-5N/140E. My thought is that while there may be a “slow down period” across roughly the west central Pacific Ocean, the time scale of this MJO is probable to be similar to the late December 2008 into early February event. The latter was roughly 30 days, the fast end of the MJO time scale. Perhaps this is a characteristic of MJOs when stochastic extratropical dynamics are heavily involved with their initiation.
One of those serious monitoring issues I have is that our current MJO will lead to the development of a slower evolving behavior of tropical convective forcing initiating across the Indian Ocean during early May. This may eventually shift east as a MJO and contribute to a significant westerly wind burst across the equatorial west central Pacific during late May/early June. Stay tuned. In any case, the on-going MJO is already impacting the USA (to make that clear), and working with GWO processes, will continue to do so for at least the next several weeks. Only a few of those concerns can be discussed below.
Through 15 April the GWO projection is weak, less than 1 standard deviation in phase space but still tilted toward the La-Nina attractor. Clearly the MJO is dominating any subseasonal signal. However, the dynamical processes represented by the GWO continue to be very important. A research issue on the WB (endless) list of things to do is to more clearly bring out some of those processes. Remember that the WB (2009) measure of the GWO is a global dynamical circulation quantity.
For instance, tied to strong southwest Pacific tropical forcing and midlatitude mountains during the past few weeks, the eddies have worked hard essentially eliminating zonal easterly wind flow anomalies across the Northern Hemisphere subtropical atmosphere. In fact, there are even ~5m/s zonal mean westerly anomalies at 200mb around 25N, and there is an accompanying AAM transports signal. This is why many areas of the USA that had been experiencing severe drought have recently been receiving much needed precipitation.
Speculating, per MJO issues discussed above along with the GWO, maybe this “AAM rally will have legs”. Stay tuned. I continue to find it very interesting what has seemingly been a recent close relationship between the AAM and DJIA time series!
Eastern Hemisphere subtropical transition (first order baroclinic mode) is well underway involving upper tropospheric anomalous twin Indian Ocean (west Pacific) anticyclones (cyclones). Loosely, a superposition of the 250mb psi snr composite anomaly plots for MJO phases 4-5 with GWO 1-3 depict the global circulation. Current Rossby wave energy dispersion (RWD) from the Indian Ocean anticyclones into the North Pacific is one of the signals the models have been catching up to the last few days. That is probable to lead to another western USA trough/eastern states ridge during week-2, a notion offered in my 11 April posting. Afterward, weeks 3-4 may see another GWO/MJO 7-8-1-2 transition suggesting an extension of the East Asian jet across the Pacific collapsing to more strong/energetic split flow western and central states troughs/closed lows. The latter would be during the first part of May, and the storm track is likely to be shifted a bit farther north than recently observed.
Weather ramifications are well understood. For the USA, after a break next week, a resumption of an active storm track pattern focusing on the western and central states appears probable. Precipitation opportunities for many drought regions should continue. Hopefully the Gulf of Mexico will recover from yet another possible late season Tehuantepecker next week.
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
http://www.wmo.ch/pages/mediacentre/news/index_en.html
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 24-26 April.
Ed Berry
Saturday, April 11, 2009
Strong MJO and Transitioning Toward ENSO Neutral: End of Story – Correct???
“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. Very warm SSTs continue across the
Flanked by weak warm anomalies ~plus 0.5C, similarly cool SSTs are present around 140-170W across the equatorial Pacific. Totals have warmed to ~26-28C over much of Nino 3 region; however, the 29C isotherm is still well to the west ~165E on the equator. Substantial warmth is still present at depth along the equatorial thermocline west of 160W at ~100-200m per latest 5-day averaged TAO buoy data. Magnitudes are around plus 2-4C.
Worth repeating from a week ago, only a few scientific matters can be discussed in this forum. Several very serious weather-climate monitoring issues exist that careful attention must be paid to heading into boreal summer. These include warming of the west
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
The most robust subseasonal signal continues to be the (pseudo) MJO. Per WH (2004) technique, through 10 April ~2.5 sigma projection in octant 2 of phase space was observed, approaching 3 standard deviations emerging into octant 3 retaining the ENSO signal (more realistic; constructively interfering with La-Nina). Full disk satellite imagery shows intense tropical forcing centered ~5N/90E, and subtropical transition to upper tropospheric twin Indian Ocean (west
Sparing other details about what appears to be a real “text book” MJO, the reader may ask, “why am I complaining about it?” As was discussed in my 4 April posting, driven by stochastic dynamical processes explained by the WB (2009) measure of the GWO, this MJO grew out of the noise in the region of
My point is that I am confident the area of enhanced tropical rainfall centered west of
As suggested above, our La-Nina base state is “reloading”, at least in terms of the zonal mean and the return of the expected asymmetric zonal wave number 1 pattern of tropical circulation anomalies. For instance, persistent anomalous easterly wind flows through out the global subtropical atmospheres (near 15-20S and 25-30N) is beginning to shift equatorward linking up with the deep tropical anomalous easterlies. Phase 3 of the MJO ~250mb snr psi composite anomaly plot reasonably depicts current tropical circulation anomalies. Global relative AAM, updated through 8 April, has been hovering ~1 sigma below the R1 data climatology. Holding it up, so to type, has been yet another one of those complicated feedbacks having details impossible to write about here.
Global relative AAM tendency has spiked to ~plus 20 Hadleys, forcing the WB (2009) measure of the GWO toward octant 4 of phase space while shifted toward the La-Nina attractor. Carefully studying various animations suggests that it is reasonable to submit that what was first a strong positive East Asian ~20 March then global mountain torque ~1 April had a contribution from the past southwest Pacific tropical forcing. Working with other extratropical processes, the linkage was established via Rossby wave energy dispersions (RWDs) from the south Pacific forcing. These were phased properly to favor anomalously high mean sea level pressures on the eastern sides of major mountain massifs including East Asia and the
A synoptic response for the
Broadly, where do we go from here? My feeling is that the tropics and extratropics will start to sync up better during the next few weeks, meaning that global AAM tendency is likely to become negative “soon” as both surface torques may contribute. I also feel there will be lingering La-Nina circulation anomalies, particularly in the zonal mean, well into boreal summer. Anomalously strong zonal mean easterly wind flows across the Southern Hemisphere subtropical atmosphere this upcoming austral winter may provide a clue of what to expect for the Northern Hemisphere 2009-10 cold season.
Repeating one of my standard excuses, any subseasonal outlook this time of year has higher uncertainty, and our current situation is adding to it. That typed, my offering that the ~250mb psi snr composite anomaly plots for GWO phases 4-5 for week-1 last weekend worked out okay. Per above, there has been extension of the jet across the north Pacific Ocean but poleward shifted in our La-Nina situation, leading to the current
Synoptically for the USA, and most numerical models are doing a reasonable job into days 5-7, another western states split flow closed low is likely next week. Afterward (roughly week-2), this split flow should consolidate while the “northern branch ridge” retrogrades. Hence there is likely to be a period of an east
Other weather ramifications, nationally and internationally, should be understood. For instance, more western
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
http://www.wmo.ch/pages/mediacentre/news/index_en.html
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 17-19 April.
Ed Berry
Saturday, April 04, 2009
No Respect Given to “Cheap MJOs”; Is There Hope from this La-Nina Hell???
“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. For the first time perhaps in more than a year, the warmest SSTs globally during the past week have been centered in the equatorial and North Indian Ocean (~5-10N/60-90E). Totals have been in excess of 30C with anomalies generally greater than plus 1C. Persistent convective suppression (until recently; discussed below) and possibly the seasonal cycle are contributing. Anomalously warm SST “pockets” have also been developing northwest of Australia and eastern Indonesia. Intense-severe tropical convective forcing focused around 10-20S/180-160W has cooled the South Pacific Ocean.
Finally, recent weak surface westerly wind flow anomalies have continued to moderate the cool Nino SSTs. SST anomalies ~minus 0.5-1C are still hanging around 140-160W in the equatorial East Pacific, with even shallow positive anomalies of similar magnitude appearing west of South America. Substantial warmth is present at depth along the equatorial thermocline west of 160W at ~100-200m per latest 5-day averaged TAO buoy data. Magnitudes are around plus 2-4C.
While only a few scientific matters can be discussed in this forum, there are several very serious weather-climate monitoring issues that attention must be paid to heading into boreal summer. These include warming of the west Pacific Ocean should westerly wind bursts (WWBs) start to occur on the equator, while atmospheric dynamical processes stubbornly try to maintain La-Nina. In the following, I am again challenged to write about exceptionally complicated and somewhat conflicting signals.
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
On face value, the strongest subseasonal atmospheric signal is the MJO. Through 3 April phase space plots employing the WH (2004) MJO measure show approximately a 2.5 sigma projection in octant 1. This is real; however, it was forced by extratropical dynamics including fast subtropical wave trains (SWT)/baroclinic wave packets (BWP) that are considered by the WB (2009) measure of the GWO. I do not want to get into details, especially when they are still in the realm of research. The point is that this MJO is a wind driven event (loosely), and perhaps analogous to a cheap non-mesocyclone EF-1 tornado that occurs when a low LCL shallow rain shower crosses a surface boundary embedded in intense shear. What are the average warning lead times for those? In any case, for forecasting purposes, it is appropriate to “play this MJO card”, for the time being.
Nevertheless, somewhat similar to December 2008, this dynamical tropical convective signal literally grew out of the noise (no SSW this time), and that is one reason why the MJO snr composite anomaly plots for 250mb psi do not accurately depict the current tropics and extratropics very well. In other words, non-oscillatory decay time scale processes (stochastic) explained by the WB (2009) measure of the GWO as opposed to truly quasi-oscillatory subseasonal tropical convective variability resulted in what the "rest of the world" now considers to be a MJO. Typically, MJOs originate around the African/Indian Ocean regions, compared to Indonesia as was observed early March 2009 and late December 2008. I submit those who take the time to understand these kinds of issues scientifically will have a better understanding of subseasonal matters/global atmospheric dynamics including making predictions (on average), than those who just use numerical model forecasts as a stand alone.
Full disk satellite imagery and other diagnostic tools clearly indicate that the strongest tropical convective forcing has been focused across the South Pacific Ocean (~15S/165W) for about the past week or so. Other tropical forcing has been occurring in the regions of tropical South America and equatorial Africa. This spatial pattern of approximately 3 centers of enhanced rainfall is a characteristic of a Western Hemisphere MJO signal.
Tying back into the monitoring issues, Hovmoller plots of OLRA have shown a slow eastward shift of tropical forcing across the southern tropics (2.5-15S) since roughly November 2008 from ~120E to 165W. The recently observed South Pacific Ocean forcing appears to be the most intense in at least a year. Broad brushing details, on interannual time scales, perhaps we are observing the most significant perturbation on what has been an extremely stubborn La-Nina base state. A respectable WWB did occur south of equator (~10m/s anomalies), and there have been a few tropical cyclone spin-ups (including Lin). Is this an indication that there will be a resumption of REAL MJOs (or coherently eastward shifting modes) leading to WWBs on the equator? Stay tuned. Perhaps we are starting to observe a forcing-response-feedback process involving the weather-climate dynamical system, and (state dependent multiplicative?) noise events leading to “cheap MJOs” during La-Nina are part of that.
Tropical convective forcing appears to be waning across the South Pacific, while slowly increasing across the warm Indian Ocean. In fact, tropical convection may be getting concentrated in the region of 90-120E. Most forecast tools do suggest convection to continue intensifying in this region during the next 2-3 weeks. Albeit shifted poleward (~35N/35S), zonal mean upper tropospheric easterly wind flow anomalies have been strengthening again, recently ~5m/s at 250mb. Global relative AAM has decreased to near 1.5 sigma below the R1 data climatology (through 1 April), and there is improving meridional symmetry of interhemispheric zonal mean zonal wind anomalies including the easterlies. Bottom line, our La-Nina base state is re-intensifying, at least for now.
On a more regional scale, and I do think this is a feedback from the South Pacific signal, while the global mountain torque is nearly zero, the East Asian component is strongly positive, ~plus 30 Hadleys. If updated today, I suspect the latter is already collapsing. That has contributed to a positive AAM tendency of ~plus 20 Hadleys forcing the WB (2009) measure of the GWO to orbit into octants 3-4 of phase space (shifted toward La-Nina). From various animations I can already see evidence that the EAJ will extend (shifted somewhat south) as a response leading to split flow across North America by week-2. Most models do show this. However, I also think this jet will collapse leading to initially “cutoff lows” across the Desert Southwest, followed by stronger and energetic baroclinically amplifying progressive full latitude western and central USA troughs. The latter may be probable late week-2 into week-3. The models are likely to struggle with the latter.
Overall, any subseasonal outlook this time of year has higher uncertainty. Our current situation is adding to it. That “excuse” typed, I think the GWO snr plots of 250mb psi (and other variables) composite anomalies for phases 4-5 week-1 then 7-8-1 week-2 are probable. Phases 2-3 may become more persistent weeks 3-4, possibly linearly superimposing upon the MJO snr composite anomaly plots of 250mb psi for phases 4-5 (in the WB (2007) GSDM sense). The latter is essentially La-Nina. Will that situation persist afterward? Stay tuned.
After a bit of a respite next week, much of the Rockies and Plains may experience exceptionally active weather again week-2, perhaps including precipitation opportunities for the southern High Plains. Should we go back to a northward shifted but energetic storm track starting week-3, drought may intensify across the southern USA once again. Other weather ramifications, nationally and internationally, should be understood.
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
http://www.wmo.ch/pages/mediacentre/news/index_en.html
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 10-12 April.
Ed Berry
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml
Please see links below for global SST details. For the first time perhaps in more than a year, the warmest SSTs globally during the past week have been centered in the equatorial and North Indian Ocean (~5-10N/60-90E). Totals have been in excess of 30C with anomalies generally greater than plus 1C. Persistent convective suppression (until recently; discussed below) and possibly the seasonal cycle are contributing. Anomalously warm SST “pockets” have also been developing northwest of Australia and eastern Indonesia. Intense-severe tropical convective forcing focused around 10-20S/180-160W has cooled the South Pacific Ocean.
Finally, recent weak surface westerly wind flow anomalies have continued to moderate the cool Nino SSTs. SST anomalies ~minus 0.5-1C are still hanging around 140-160W in the equatorial East Pacific, with even shallow positive anomalies of similar magnitude appearing west of South America. Substantial warmth is present at depth along the equatorial thermocline west of 160W at ~100-200m per latest 5-day averaged TAO buoy data. Magnitudes are around plus 2-4C.
While only a few scientific matters can be discussed in this forum, there are several very serious weather-climate monitoring issues that attention must be paid to heading into boreal summer. These include warming of the west Pacific Ocean should westerly wind bursts (WWBs) start to occur on the equator, while atmospheric dynamical processes stubbornly try to maintain La-Nina. In the following, I am again challenged to write about exceptionally complicated and somewhat conflicting signals.
http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html
http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html
http://www.pmel.noaa.gov/tao/jsdisplay/
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
http://www.cdc.noaa.gov/map/images/sst/sst.long.time.io.gif
On face value, the strongest subseasonal atmospheric signal is the MJO. Through 3 April phase space plots employing the WH (2004) MJO measure show approximately a 2.5 sigma projection in octant 1. This is real; however, it was forced by extratropical dynamics including fast subtropical wave trains (SWT)/baroclinic wave packets (BWP) that are considered by the WB (2009) measure of the GWO. I do not want to get into details, especially when they are still in the realm of research. The point is that this MJO is a wind driven event (loosely), and perhaps analogous to a cheap non-mesocyclone EF-1 tornado that occurs when a low LCL shallow rain shower crosses a surface boundary embedded in intense shear. What are the average warning lead times for those? In any case, for forecasting purposes, it is appropriate to “play this MJO card”, for the time being.
Nevertheless, somewhat similar to December 2008, this dynamical tropical convective signal literally grew out of the noise (no SSW this time), and that is one reason why the MJO snr composite anomaly plots for 250mb psi do not accurately depict the current tropics and extratropics very well. In other words, non-oscillatory decay time scale processes (stochastic) explained by the WB (2009) measure of the GWO as opposed to truly quasi-oscillatory subseasonal tropical convective variability resulted in what the "rest of the world" now considers to be a MJO. Typically, MJOs originate around the African/Indian Ocean regions, compared to Indonesia as was observed early March 2009 and late December 2008. I submit those who take the time to understand these kinds of issues scientifically will have a better understanding of subseasonal matters/global atmospheric dynamics including making predictions (on average), than those who just use numerical model forecasts as a stand alone.
Full disk satellite imagery and other diagnostic tools clearly indicate that the strongest tropical convective forcing has been focused across the South Pacific Ocean (~15S/165W) for about the past week or so. Other tropical forcing has been occurring in the regions of tropical South America and equatorial Africa. This spatial pattern of approximately 3 centers of enhanced rainfall is a characteristic of a Western Hemisphere MJO signal.
Tying back into the monitoring issues, Hovmoller plots of OLRA have shown a slow eastward shift of tropical forcing across the southern tropics (2.5-15S) since roughly November 2008 from ~120E to 165W. The recently observed South Pacific Ocean forcing appears to be the most intense in at least a year. Broad brushing details, on interannual time scales, perhaps we are observing the most significant perturbation on what has been an extremely stubborn La-Nina base state. A respectable WWB did occur south of equator (~10m/s anomalies), and there have been a few tropical cyclone spin-ups (including Lin). Is this an indication that there will be a resumption of REAL MJOs (or coherently eastward shifting modes) leading to WWBs on the equator? Stay tuned. Perhaps we are starting to observe a forcing-response-feedback process involving the weather-climate dynamical system, and (state dependent multiplicative?) noise events leading to “cheap MJOs” during La-Nina are part of that.
Tropical convective forcing appears to be waning across the South Pacific, while slowly increasing across the warm Indian Ocean. In fact, tropical convection may be getting concentrated in the region of 90-120E. Most forecast tools do suggest convection to continue intensifying in this region during the next 2-3 weeks. Albeit shifted poleward (~35N/35S), zonal mean upper tropospheric easterly wind flow anomalies have been strengthening again, recently ~5m/s at 250mb. Global relative AAM has decreased to near 1.5 sigma below the R1 data climatology (through 1 April), and there is improving meridional symmetry of interhemispheric zonal mean zonal wind anomalies including the easterlies. Bottom line, our La-Nina base state is re-intensifying, at least for now.
On a more regional scale, and I do think this is a feedback from the South Pacific signal, while the global mountain torque is nearly zero, the East Asian component is strongly positive, ~plus 30 Hadleys. If updated today, I suspect the latter is already collapsing. That has contributed to a positive AAM tendency of ~plus 20 Hadleys forcing the WB (2009) measure of the GWO to orbit into octants 3-4 of phase space (shifted toward La-Nina). From various animations I can already see evidence that the EAJ will extend (shifted somewhat south) as a response leading to split flow across North America by week-2. Most models do show this. However, I also think this jet will collapse leading to initially “cutoff lows” across the Desert Southwest, followed by stronger and energetic baroclinically amplifying progressive full latitude western and central USA troughs. The latter may be probable late week-2 into week-3. The models are likely to struggle with the latter.
Overall, any subseasonal outlook this time of year has higher uncertainty. Our current situation is adding to it. That “excuse” typed, I think the GWO snr plots of 250mb psi (and other variables) composite anomalies for phases 4-5 week-1 then 7-8-1 week-2 are probable. Phases 2-3 may become more persistent weeks 3-4, possibly linearly superimposing upon the MJO snr composite anomaly plots of 250mb psi for phases 4-5 (in the WB (2007) GSDM sense). The latter is essentially La-Nina. Will that situation persist afterward? Stay tuned.
After a bit of a respite next week, much of the Rockies and Plains may experience exceptionally active weather again week-2, perhaps including precipitation opportunities for the southern High Plains. Should we go back to a northward shifted but energetic storm track starting week-3, drought may intensify across the southern USA once again. Other weather ramifications, nationally and internationally, should be understood.
Appendix
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We appreciate all the support!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
http://www.cdc.noaa.gov/forecasts/clim/
The following are links to information about the stratosphere and other nice monitoring tools:
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html
http://code916.gsfc.nasa.gov/Data_services/met/ann_data.html (new stratosphere link!)
The following is a link to NCEP model verifications (surf around for lots more):
http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html
The following is a link discussing recent global weather and related events:
http://www.wmo.ch/pages/mediacentre/news/index_en.html
These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:
http://ams.allenpress.com/archive/1520-0493/preprint/2008/pdf/10.1175_2008MWR2686.1.pdf
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 10-12 April.
Ed Berry
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