Deep in the “Strange Brew” of La-Nina and SSW; Several Rounds of USA High Impact Weather are Likely Weeks 1-3

“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

Map room issues continue and are being worked on.

Please see links below for SSTs. Strengthening trades during the last week has renewed cooling of SSTs across all Nino regions. TAO buoy data show 5-day averaged anomalies ~minus 1-1.5C along the equatorial Pacific Ocean cold tongue, with the 29C total SST isotherm back to near 160E. Our downwelling oceanic Kelvin wave (~150m depth) may be loosing some coherence as it propagates into the east Pacific. SSTs have also cooled across the west central and Southwest Pacific Ocean with totals generally less than 30C. The latter is likely a response to the recent strong tropical convective flare-up ~10S/160E about a week ago.

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/forecasts/sstlim/Seas.html (note the initial projection)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

The global weather-climate situation is extremely complicated. While I do feel comfortable with any diagnosis I can offer, this medium of communication is not a good facilitator. From my viewpoint of the global ocean-land-atmosphere dynamical system, La-Nina is well entrenched. Tropical convective forcing has consolidated nicely ~0/130-140E extending from the East Indian Ocean into the SPCZ. WH (2004) MJO phase space plots show greater than 2 sigma projections in octant 5 without ENSO and approaching a nearly 3 standard deviation anomaly with it. However, this empirical technique reflects what I think is a resurgence of our quasi-stationary La-Nina base state. I do not think we have an eastward propagating signal like that observed during early-mid January. Phase 5 of the WH (2004) measure of the MJO OLRA snr composite plot nicely depicts the current situation of tropical rainfall.

The wind and convective signals are loosely getting back into sync, as are the tropics and extratropics. A “messy” Eastern Hemisphere subtropical transition to anomalous upper tropospheric East Indian Ocean (central Pacific) twin anticyclones (cyclones) continues. The latter is the zonally asymmetric component of tropical wind anomalies characteristic of a cold event.

However, similar to a year ago and not cleanly observed during this “encore”, there is now respectable interhemispheric meridional symmetry of zonally symmetric zonal mean zonal wind anomalies. These include ~5m/s 200mb zonal mean easterly wind flow anomalies throughout the Northern Hemisphere subtropical atmosphere, and easterly anomalies in excess of 10m/s ~75N (more said below). Reflective of a poleward shifted zonal mean polar jet; 200mb westerly wind flow anomalies of roughly 5m/s exist at 45N.

Also similar to the 2007-08 strong El-Viejo, the Northern Hemisphere midlatitude circulation is characterized by anomalous ridges suggesting a positive phase of a Branstator (2002) circumglobal teleconnection. Phase 3 of the GWO 250mb psi snr composite anomaly plot depicts this situation. Along with phase 4 for the MJO depicting tropical anomalies, a superposition of these composites is broadly representative of the global circulation. This response may continue for the next several weeks.

Updated through 3 February, global relative AAM is ~1.5-2 sigma below the R1 data climatology, an upward trend from its low of ~minus 2.5 sigma a couple of weeks ago (bear atmosphere rally?!). Including contributions from the surface torques, relative AAM tendency has increased to ~plus 15 Hadleys the last week or so. However, the WB (2009) measure of the GWO remains locked in octants 3-4 of phase space, strongly shifted toward the La-Nina attractor comparable to that observed during the 2007-08 boreal winter/spring. I do think a slow orbit is probable during the next few weeks, tilted toward La-Nina.

The record breaking (data going back to 1978) major sudden stratospheric warming (SSW) continues. See links in the Appendix for details. The zonal wave number 2 pattern of Northern Hemisphere higher latitude anomalous continental cyclones (~100E ad 100W) and ocean ridges bridging the pole has propagated down to at least 200mb. Surface weather across large portions of the Northern Hemisphere is already being impacted. A synoptic response has been for the European blocking (which played a role in the recent UK snowstorm) to retrograde into central Atlantic Ocean. The latter does not (yet) project strongly on the negative phase of the NAO, and serves as another example why it is important to understand the dynamics of teleconnections (the Rottweiler is always watching!).

In any case, arguably GWO processes starting December 2008 contributed to the SSW, and now the SSW is feeding back to the GWO. For instance, the polar latitude strongly anomalous upper tropospheric zonal mean easterly wind flow is helping to keep global AAM low, in a sense constructively interfering with La-Nina. Furthermore, AAM eddy transports from both the subtropics and high latitudes may be contributing to the anomalous westerly wind flow ~45N. Regardless of the details, working with what may be a maturing quasi-stationary La-Nina base state, tropospheric impacts from the SSW will continue for the next several weeks. Stratospheric time scales are very slow.

Regionally, the central Pacific Ocean ridge-expanding western USA states trough is probable to continue through the next 2-3 weeks. Blocking retrogression through Canada, perhaps bridging the Atlantic and Pacific Ocean ridges, is likely to keep an active storm track over much of the central and southern lower 48 states (in contrast to the poleward displaced zonal mean polar jet). There may be a period of anomalous cold and wet for much of the country, including an elevated risk of high impact weather (all types; should be understood), particularly ~week-2.

Somewhat typical of a La-Nina, much of the Arctic air (surface temperatures well under minus 50F across Siberia) is displaced toward Asia. However, some of this air will “bleed” back into the USA the next few weeks, ending the current respite from the cold winter for locations such as the Upper Mississippi Valley. Speculating farther, while March-June 2009 may have weather similarities to that period during 2008, the seasonal northward migration of the polar jet may be delayed. Including impacts from the severe tropical thunderstorm activity centered on Indonesia and northern Australia, I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide.

Appendix

The formal announcement including an additional expanded outline for the 24 February 2009 one-day (~830am-530pm MST) workshop on the WB (2009) GWO has been released through various mailing lists, and is available on the ESRL/PSD GSDM web link. Let me know if you have not seen it. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”.

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

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 awaiting publication in MWR. A pdf of an in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.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, and unscientific!

Discussions will be very difficult to publish the next few weeks given shift work and preparations for the GWO workshop. I will attempt to post “something” ~13-15 February.

Ed Berry

Update: La-Nina + Major SSW = Where the Atmosphere has Never Gone Before?

“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

Some map room plots are still missing due to on-going upgrades. These issues are being worked on.

This will again be short! Please see links below for SSTs. Local and relatively shallow warming of equatorial Pacific Ocean SSTs has occurred west of South America, similar to a year ago. Anomalies are ~plus 1-2C. Tropical-extratropical interactions linked to the recent strong MJO and seasonal issues may be contributing. Our respectable downwelling oceanic Kelvin wave ~150m depth has propagated to about 150W. Any future impacts from the latter are unclear. Stay tuned. The warmest SSTs globally persist across the southwest Pacific, with totals ~30C in the region of New Guinea.

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 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

La-Nina is reloading. Tropical convective forcing has returned to the Eastern Hemisphere with some consolidation ~0/120E while a somewhat separate region persists across the warm southwest Pacific Ocean. The MJO signal has weakened. There is little projection in WH (2004) phase space removing interannual component, but ~1.5 sigma in octant 3 (through 28 January) retaining it, reflecting the resurgence of La-Nina. Monitoring will tell if another eastward propagating signal of tropical forcing evolves. Other options include two areas such as a quasi-stationary Indonesian region concurrently with episodic southwest and west central Pacific strong to severe tropical convection.

Global relative AAM is approaching negative anomaly magnitudes comparable to the 2007-08 strong La-Nina. Updated through 26 January, AAM was ~2.5 sigma below the R1 data climatology forcing the WB (2009) measure of the GWO deeply (~2 sigma) into octants 2-3 of phase space. Zonal mean easterly wind flow anomalies have become quite strong throughout the equatorial and subtropical atmospheres, ~5-10m/s at 200mb, and up to 15m /s across Northern Hemisphere polar latitudes. The latter is a response to a sudden stratospheric warming (SSW; more said below). A loose superposition of phase 3 for both the 250mb snr psi composite anomaly plots of the MJO and GWO generally represent the global circulation, and that should continue for at least the next 2-3 weeks. This means our familiar pattern of anomalous midlatitude ridges including the central Pacific Ocean favoring a trough in the region of western North America.

Forced by (unpredictable) dynamical processes responsible for the strong west coast ridge a couple of weeks ago (see 23 January posting), a major SSW is in progress. In fact, data records going back to 1978 (see new stratosphere monitoring link in the Appendix) suggest this SSW is the strongest given this time of year. A well pronounced zonal wave number two circulation structure in the stratosphere is present, with lobes of the polar vortex across the Arctic latitudes of North America and Asia. Interacting with the La-Nina base state, the troposphere is already being impacted, and that will continue for at least the next several weeks. Large anomalies of zonal mean easterly wind flow is propagating downward into the upper troposphere of the Northern Hemisphere high latitudes as I type.

Synoptically, a possible regional-scale response is for tropospheric blocking initially across Scandinavia to retrograde through the North Atlantic and Canada then into the North Pacific Ocean during the next few weeks. The NCEP GEFS and other ensembles are starting to capture this scenario. That suggests the storm track should shift south across the lower 48 states of the USA later week-2 and perhaps continue most of February. Additional feedbacks (not discussed) from the South Pacific Ocean tropical forcing may also contribute to bringing the storm track farther south. Areas that have been anomalously dry this winter may get much needed precipitation. In fact, there may be some weather similarities to February 2008 across the USA next month. I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide.

Appendix

The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists. An extended outline was sent today, 30 January, which should also be avialable from the ESRL/PSD GSDM web link. Let me know if you have not seen it. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”.

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from thefollowing link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.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! I plan on posting at least an abbreviated discussion on ~7 February 2009.

Ed Berry

Reloading La-Nina, but with a SSW twist???

“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

Many map room plots are missing due to on-going upgrades. These issues are being worked on.

This will be short! Some warming of SSTs has occurred across the far west central equatorial Pacific Ocean (totals ~30C) as well as the west of South America. The latter may be a similar occurrence to a year ago. Overall, global SSTs remain “steady state” including ~minus 1C anomalies (warmed slightly) across all Nino regions.

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 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

The global ocean-land-atmosphere dynamical system is recovering from the recent strong perturbation on La-Nina. Importantly, linked to MJO convection across the South Pacific Ocean at the time, there was large amplitude meridionally directed Rossby wave energy dispersion (RWD) across the North Pacific Ocean (with Southern Hemisphere symmetry). The RWD forced the westward shifted PNA ridge that was responsible for the severe cold outbreak centered on the Upper Mississippi Valley last week. Several diagnostics (including EP fluxes) indicate that tropospheric wave energy from this RWD has propagated into the stratosphere and a sudden stratospheric warming (SSW) may have been initiated. More said below.

The MJO signal is centered on Africa, and interactions with extratropical wave energy propagations are intensifying deep convection across the equatorial Indian Ocean. Zonal mean easterly wind flow anomalies (~5m/s at 200mb) have returned to the tropical and subtropical atmospheres. Updated through 21 January, global relative AAM is already ~2sigma below the R1 data climatology, the lowest since early October 2008. I do expect a further decline (like our recent financial markets!).

Summing up, a coupled GWO/MJO evolution from octants 7-8 the last week or so into at least 3-4 in phase space is likely the few weeks, constructively interfering with La-Nina. The global circulation shown by ~phase 3 of the 250mb snr psi composite anomaly plots for the GWO and MJO appears probable by week-2. This means our familiar pattern of anomalous midlatitude ridges, including the central Pacific Ocean ridge and a downstream trough in the region of western North America.

Regionally, the on-going discontinuous PNA retrogression is similar to that observed early December 2008. This is being forced by the current weakened La-Nina base state including residual Indonesian tropical forcing. As La-Nina reloads the next few weeks, troughing is likely to return to the Gulf of Alaska then extend into western North America. In contrast to the high confidence outlooks for the USA issued November 2008 for December, it is unclear how far southeast these next series of troughs may extend into the western USA. Should the storm track remain anomalously shifted poleward, dryness may intensify over portions of (for example) the central and southern Plains. Typical of a La-Nina base state, the Northern Hemisphere polar vortex retracted during late December, and that has been the case until very recently.

However, unusual for La-Nina, and essentially not observed during the 2007-08 cold event, a serious monitoring issue the next 30-40 days will be if a possible SSW disrupts the polar vortex. Depending on timing of behaviors, including the possibility of another MJO coming out from the Indian Ocean into the west Pacific ~weeks 3-5, there may be significant weather impacts on the USA which are currently unclear. Stay tuned. I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide.

Appendix

The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists, and is available on the ESRL/PSD GSDM web link (cited above). Let me know if you have not seen it. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”.

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

The following is a link to information about the stratosphere and other nice monitoring tools:

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from thefollowing link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.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! I plan on posting at least an abbreviated discussion on ~30 January 2009.

Ed Berry

Update: Rogue “MJO Wave”, then “La-Nina Reloaded”

“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

The 91-day signal to noise ratio (snr) anomaly composites are being updated daily. There are still map room issues that are being worked on. WB (2009), part-1 of a 2 part paper where the GWO is formally introduced, is in press for MWR publication. There is a link in the Appendix to download the manuscript.

The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists. It can also be obtained from the GSDM web page per above link. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”. The workshop is open all interested; private, government, etc..

This posting is significantly abbreviated due to upcoming travel. In fact, I would like that to be a trend, particularly if a real-time web page with "maps and figures", as a component of the GSDM site, can evolve.

Global SSTs remain relatively steady state, as would be expected since their anomalies are generally slowly evolving. Slight warming has been occurring across the convectively suppressed South Indian Ocean, while a downwelling Kelvin wave continues its slow propagation into the Western Hemisphere equatorial Pacific Ocean. The latter, forced by weakened trades and actual surface westerlies, is ~150m deep having anomalies roughly plus 2-3C per latest 5-day averaged TAO buoy data. Subsequent impacts, if any, are unclear.

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 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

A much stronger than expected MJO signal is propagating through the Western Hemisphere, located in octant 7 of WH (2004) phase space with and without the interannual retained. For this case, the ~2.5 sigma projection without ENSO is realistic (there are reasons). Satellite imagery and other tools suggest the MJO dynamical signal is centered on the Americas, with an eastward propagation phase speed of ~20-25m/s. These do progress significantly faster across the Western Hemisphere. I expect the MJO to easily re-emerge into the Indian Ocean during week-2.

While arguably unpredictable with appreciable lead-time, I am not surprised by this “rogue MJO”, and I do think scientifically defensible attribution can be offered (perhaps as one of the cases for the GWO workshop). In fact, concerns of this possibility including weather impacts were expressed in discussions last (boreal) fall. The gist is red noise dynamical processes captured by the WB (2009) measure of the GWO, working with the annual cycle, likely forced the coherent eastward propagating convective signal (south of the equator) projecting on a MJO.

The circulation response has included subtropical transition of upper tropospheric anomalous anticyclones (cyclones) to cyclones (anticyclones) across the Indian Ocean (west Pacific Ocean), and extension the East Asian jet (EAJ) forcing a large positive phase (shifted west) of the Pacific North American teleconnection (PNA). Phases 6-7 of the MJO 250mb snr psi composite anomaly plots depict the global tropical and even extratropical circulation. The recent severe USA cold Arctic outbreak that focused on the northern and central Plains-Northeast is directly linked to all the above.

The GWO (R1 data AAM plots updated through 15 January) has shown little variation and projection since early this month, shifted slightly toward La-Nina in phase space, suggestive of the on-going interannual component. However, just as the MJO destructively perturbed La-Nina, rapid constructive interference is very likely the next 1-3 weeks as it's signal returns to the Eastern Hemisphere. The surface torques are collectively becoming negative contributing to an already ~minus 20-30 Hadley AAM tendency. A sink-source zonal mean AAM poleward transport signal has also appeared across the subtropical and midlatitude atmospheres of the Northern Hemisphere. Hence the GWO has spiked into octant 1 of phase space. I do think a relatively synchronized GWO/MJO 7-8-1 transition is starting, and all that should lead to a global circulation depicted by phases 2-3 of the 250mb snr psi composite anomaly plots. As is typical during these types of regime transitions (on our list to quantify), all global numerical weather prediction models have been struggling badly the last several days.

The long awaited PNA discontinuous retrogression will start week-1, responding to lingering Indonesian tropical forcing. The “western trough/southeast ridge pattern” should mature by ~ week-3 as Eastern Hemisphere tropical forcing intensifies, having USA weather ramifications similar to December 2008. Monitoring will tell if this situation “locks in”. Remember that while also stronger than expected, the 2008-09 La-Nina encore is still “pale” by comparison to a year ago (as is typical). In any case, keeping in mind climatology, I do have some concern of one or two significant/severe baroclinic winter storm developments focusing on the Plains roughly weeks 2-3. There should also be concerns that at least portions of the Plains during the next several months may have weather ramifications similar to late winter-spring 2008.

Intense to severe tropical thunderstorm activity is probable to shift from South America and South Africa week-1 into the equatorial/South Indian Ocean week-2 (a large change). The focus should be from the Indian Ocean into Australia and Indonesia by week-3. The lingering convection currently centered on Indonesia is a response to the La-Nina global circulation base state.

I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide, including official statements for tropical cyclones that are likely to impact regions such Madagascar week-1. Locations farther east including northern Australia will have an increased tropical cyclone risk weeks 2-4. Portions of particularly Western Europe may have several rounds of intense/severe wind and rain during the next couple of weeks.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

The following is a link to information about the stratosphere and other nice monitoring tools:

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

In addition to the subseasonal snr composite anomaly plots, we hope near real-time discussions with “weather maps” will 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! I plan on posting at least an abbreviated discussion on ~24 January 2009.

Ed Berry

The Devil Deals the Atmosphere; PNA Retrogression or Bust!!!

“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

The 91-day signal to noise ratio (snr) anomaly composites are being updated daily. There are still map room issues that are being worked on. WB (2009), part-1 of a 2 part paper where the GWO is formally introduced, is in press for MWR publication. There is a link in the Appendix to download the manuscript.

These discussions are a component of an experimental effort involving linking weather and climate. The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists. If you have not received this, please leave a comment with your email address, and I will forward. Hopefully we can place this information on the above GSDM web link ASAP.

The general spatial pattern of global SSTs and their anomalies persist (see links). Tied to recent variations of atmospheric and tropical forcing (more said below), a slight lessening of the cool Nino anomalies has occurred during the past week (~minus 1-2C per 5-day averaged TAO buoy data). In fact, there is a downwelling oceanic Kelvin wave ~100-200m deep crossing the Dateline. The very warm waters of the Southwest Pacific Ocean have cooled substantially with totals generally less than 30C.

In any case, in terms of the global ocean-land-atmosphere dynamical system, La-Nina is well established. The expected re-emergence became notable by about October 2008, atypical timing based on our limited sample size. Consistent with “encores”, our on-going La-Nina is weaker (but more robust than earlier anticipated by myself) than a year ago (per GWO, MEI, SSTs, etc.).

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 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

During the past 1-2 weeks the wind and convective signals did reasonably get back into sync. The result has been a perturbation destructively interfering with La-Nina. Behaviors similar to this were observed relatively frequently during the strong 2007-08 cold event. Unlike a year ago, however, the quasi-stationary component of the global circulation has been the most dominate.

In my last posting (3 January 2009; 38^th anniversary of the Great Plains Blizzard for those who remember!), I stated “there is no coherent MJO”. While not entirely inaccurate, I did underestimate what stochastic forcing represented by the WB (2009) measure of the GWO can do.

Recalling the rapid eastward flows of wave energy through the Eastern Hemisphere subtropical atmospheres per past postings, to keep things “short/simple”, I hypothesize that the seasonal/annual cycle became involved. In other words, the flow of wave energy forced tropical convection to propagate east-southeast into the warm southwest Pacific Ocean. The result was a fading in of a weak MJO signal. As I type, upper tropospheric cross-equatorial divergent outflow from this tropical forcing is leading to an extension of the East Asian jet (discussed below). The astute reader will recall discussions of this possibility were previously given. Yes, a real-time web site with maps and figures would help show these kind of behaviors!!!

Full disk satellite imagery and other tools illustrate a large region of intense to severe tropical rainfall centered ~10S/140E extending from Indonesia to the South Pacific islands. There is evidence some separation is occurring, with one region starting to focus on Indonesia and other ~15S/170E. If there is still any MJO signal, the latter region of enhanced convection would be part of it. Updated through 9 January, per WH (2004) MJO measure retaining ENSO, there was ~1 sigma projection in octant 5 of phase space. Regardless, I do think the Eastern Hemisphere tropical forcing will be dominant during the next several weeks.

In spite of the large global AAM tendency observed late December (calculated tendency ~plus 25 Hadleys), global relative AAM has remained below the R1 data climatology (through 8 January). That tells us the La-Nina base state is “holding” (for reasons). Forcing this large tendency included indirect contributions from zonal mean AAM flux convergence ~35N (with some interhemispheric symmetry) due to the midlatitude baroclinic eddies, and north-south mountains. Perhaps responding to complicated extratropical feedbacks from the South Pacific Ocean tropical forcing (ex., Rossby wave energy dispersions (RWDs) arcing through the North Atlantic Ocean; need maps to show!), even though the global mountain torque signal is decreasing, the East Asian component is ~plus 30 Hadleys. These processes are working to extend the East Asian jet (with an accompanying strong cold outbreak) which will amplify the evil ridge from Hell just off the North American coast next week; a.k.a. the positive phase of the PNA.

Cutting to the chase, I expect to see constructive interference involving various dynamical processes reloading La-Nina during the next several weeks. Many of the components are captured by the WB (2009) measure of the GWO. I am optimistic that the wind and convective signals will remain coupled.

Animations of upper tropospheric daily mean vector wind anomalies present a “distorted” and perturbed configuration of the La-Nina zonally asymmetric spatial pattern for the tropical circulation observed since at least October 2008. There are loose twin anticyclones centered on the Indian Ocean but the cyclones have shifted to 150W. However, divergence is also increasing across the Indian Ocean. I do think by later week-2 into week-3 much of the Indian Ocean into Australia and Indonesia will be strongly active, especially south of the equator. Hence it is likely the twin tropical cyclones will redevelop west of the Dateline.

Global relative AAM tendency is already becoming weakly negative. While there will be variations, that negative tendency may become quite large perhaps forcing AAM to ~2 sigma below the R1 data climatology later this month. Supportive of this notion is zonal mean easterly wind flow anomalies are returning to the subtropical atmospheres, and AAM is starting to flux poleward.

The GWO is slowly completing its 4^th orbit in phase space during the last 90 days. While there is currently little projection, per above a shift into octants 8-1 while settling into 2-3 of phase space is probable. The latter has been the 90-day trend, meaning a drift toward the La-Nina attractor. Phase 5 for both the MJO and GWO 250mb snr psi composite anomaly plots loosely depict the current tropical and extratropical circulations, respectively. Phases 8-1 then 2-3 of these plots are the most probable to depict the global circulation weeks 2-4. Synoptically, albeit apparently “delayed” by ~5-10 days (timing always has a noise contribution!), the wicked ridge of the west is likely to discontinuously retrograde perhaps to ~150-160W going into February. That would admit troughs into the western and central USA. During the last few days, week-2 numerical ensembles have been starting to latch-on to this proposed forecast solution.

One of the numerous issues not discussed is that the Northern Hemisphere polar vortex is currently retracted. As the Eastern Hemisphere tropical forcing intensifies, the polar vortex is likely to expand across central and east Asia. However, if not, the East Asian jet may retract so much such that troughs may eventually dig into the Gulf of Alaska ending any possible cold situation across USA. That almost did occur roughly 10 days ago. Having my reasons, I do not think a situation like the 1975-76 USA winter is likely.

Weather impacts per above across the country are already well known. Forced by the oncoming transient +PNA, models have been correctly predicting an Arctic outbreak initially focused Upper Mississippi Valley/Great Lakes starting early next week. That cold air will spread into the eastern states. Care must be taken not to underestimate the ramifications of this airmass given its source. Temperature and precipitation anomalies having similarities to much of December 2008 may then revisit the lower 48 states after ~20 January and persist well into February. That includes the most probable high impact weather from that type of regime.

Dryness is becoming an increasing concern for locations such as California and the southern/central High Plains. As the retrogression occurs starting week-2, it is quite possible the expanded North Pacific Ocean jet will impact most the USA west coast with welcome precipitation for California.

Intense to severe tropical thunderstorm activity will remain generally persistent from Indonesia into the northern Australia for at least the next several weeks. While the South Pacific Ocean will continue to be the “wild card”, some lessening of thunderstorm activity should occur week-1. Much of tropical South America and South Africa may become anomalously active week-1 and perhaps continue week-2. Per above, later week-2 and possibly well into February much of the central and eastern Indian Ocean through Indonesia and Australia may have significant convective enhancement, linked to our quasi-stationary La-Nina regime. I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide (ex., recent cold in Europe) including official statements for tropical cyclones (ex., Dondo) that are likely to impact regions such as around Australia and Madagascar during the next several weeks.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

The following is a link to information about the stratosphere and other nice monitoring tools:

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

In addition to the subseasonal snr composite anomaly plots, we hope near real-time discussions with “weather maps” will 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! I plan on posting at least an abbreviated discussion on 17 January 2009.

Ed Berry

La-Nina well Entrenched -- PNA Retrogression Likely ~Days 10-20

“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

The 91-day signal to noise ratio (snr) anomaly composites are being updated daily. There are still map room issues that are being worked on. WB (2009), part-1 of a 2 part paper where the GWO is formally introduced, is in press for MWR publication. There is a link in the Appendix to download the manuscript.

These discussions are a component of an experimental effort involving linking weather and climate. We are moving forward on plans for having a one-day workshop in Boulder on 24 February 2009 discussing the WB (2009) GWO. Our announcement is forthcoming; stay tuned.

The spatial pattern of global SSTs is unchanged (see links). There has been ~1C cooling across the southwest Pacific Ocean during the last week (due to intense frontal (SPCZ) rainfall) with slight warming across the Indian Ocean. In fact, significant warm anomalies (~2C/~29C totals) are present over the southwest Indian Ocean in the region of Madagascar.

Substantial negative SST anomalies (~1-2C per 5-day averaged TAO buoy data) are present along the equator (within 5 deg lat) from 160E to the coast of South America. These cold anomalies are deep, extending to ~200m depth east of 160W, with magnitudes ~minus 5C. This subsurface is similar to a year ago, meaning a steeper than normal oceanic thermocline that is typical of a mature basin wide cold event. While we expected a La-Nina encore as early as late September 2008, the magnitude of the cool SST anomalies across all Nino regions has exceeded my expectations. Again, this is a response to the global ocean-land-atmosphere dynamical system (the WB (2009) measure of the GWO attempts to represent some of this), and is not good news for (example) probable drought prone areas in this situation (such as USA southern and central High Plains).

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 18)

http://www.cdc.noaa.gov/map/images/sst/sst.long.time.gif

The issue of wind and tropical convective signals syncing up continues. Since October 2008 there have been 4 coherent episodes of when these signals “faded in and out” in terms of coupling. Taking into considering numerous time-scales involving complicated feedbacks that I will not discuss in an inefficient manner such as these blog writings, the periodicity has been ~30 days. After the large (~3 sigma) October and November GWO orbits in phase space involving octants 4-5 to 8-1 then 4-5, a weaker rendition occurred from roughly 8-18 December leading to the current variation. Updated through 1 January 2009, the WB (2009) measure of the GWO was in ~octant 4 of phase space. Each one of these orbits in GWO phase space has been seemingly spiraling toward octants 2-3, the La-Nina attractor for our purposes.

There is no coherent MJO, which has been the case since the truncated October 2008 spatial variation of tropical rainfall anomalies projecting onto this mode. Starting during November, a general consolidation ~0/120E of intense to severe tropical thunderstorm activity has been in progress. Updated through 1 January 2009, retaining the very important interannual and ENSO signals, the WH (2004) measure of the MJO had nearly a 2 sigma projection in octant 5 of phase space. This is, in reality, a quasi-stationary La-Nina mode of tropical forcing centered on Indonesia, and it does appear the wind signal is trying to get back in line. Phases 4-5 of both the GWO and MJO 250mb psi composite anomaly plots loosely depict the extratropical and tropical circulations, respectively.

Per animations of upper tropospheric daily mean vector wind anomalies, the flow of wave energy tied to the ~8-18 December variation can be observed coherently propagating into the Eastern Hemisphere subtropical atmospheres just before Christmas. That led to strong meridionally directed Rossby Wave energy dispersions (RWDs) into the extratropical Northern and Southern Hemispheres leading to poleward shifting of anomalous zonal mean easterly wind flow (to ~45-60 N/S). Zonal mean equatorward flux convergence of AAM increased ~40N around this time (loosely) leading to an acceleration of westerly wind flow at that latitude. Synoptic responses have included strong North Atlantic Ocean blocking (an example of why the NAO is red noise) and a retracted Northern Hemisphere polar vortex. In fact, the latter may explain the recent anomalous cooling in the stratosphere.

Baroclinic wave energy associated with the ongoing GWO orbit is currently propagating into the Eastern Hemisphere, interacting with the circulation anomalies discussed in the previous paragraph. Similar to the November 2008 GWO orbit (~40 days ago), a positive global mountain-negative frictional torque index cycle variation is occurring (see AAM plots). The positive mountain torque has a large contribution from East Asia, ~20 Hadleys. Fighting the La-Nina base state, a poleward shifted extension of the East Asian/North Pacific Ocean jet is occurring as I type. All models have captured this jet, and correctly predict a positive phase of the PNA teleconnection by late week-1.

The last 2 paragraphs were written to show an example of a forcing-response-feedback loop linking global to zonal mean to regional-scale circulation anomalies. The WB (2009) measure of the GWO, lined up with the tropical forcing, is probable to orbit into octants 8-1 of phase space during the next 1-2 weeks. Observe that in spite of a ~30 Hadley calculated positive AAM tendency, global relative AAM is still below the R1 data climatology (after a 3 sigma decrease from November). Hence, perhaps similar to early-mid December, any ridge from Hell that may evolve along the USA west coast is likely to retrograde after day 10 as the North Pacific Ocean jet retracts. The ridge may shift back to ~150-160W by roughly week-3, and possibly allow cold troughs to dig along the west coast. Models already are, and will continue to play “catch-up” to this situation. My confidence is at least moderate with this notion, given our well defined La-Nina global circulation involving Eastern Hemisphere tropical forcing and strong meridional symmetry of zonal mean and regional circulation anomalies.

Phases 4-5 of the GWO snr 250mb psi composite anomaly plots are probable to depict the extratropics week-one followed by 8-1-2 by late week-two and week-three. Whether or not we lock-in to a superposition of GWO and MJO circulation anomalies shown by ~phases 2-3 of the 250mb snr psi (and temperature) composite anomaly plots for a JFM mean is still unclear. Regardless, a La-Nina situation of at least repeated progressive troughs into the western and central USA is probable. That may be along a northward shifted storm track favoring southwest flow across the Plains. Arctic air may focus from the northern and central Rockies into the Plains and Upper Mississippi Valley. Again, there will be variations due to feedbacks.

Weather ramifications including additional high impact weather should be well understood. In fact, the JFM 2009 seasonal mean outcome for temperature and precipitation is likely to have some similarities to JFM 2008. While anomalous wetness is probable from the Pacific Northwest into the Ohio Valley, significant/severe drought conditions may re-emerge for locations such as the central and southern High Plains (including western Kansas) by boreal spring. I had some optimism during fall the latter would not occur, and hopefully there will still be decent precipitation.

Intense to severe tropical thunderstorm activity is probable to persist from Indonesia into at least northern Australia “UFN” (centered ~120E), slowly shifting south. Locations around the SPCZ and tropical South America are likely to have some enhancement week-1, and anomalously intense rainfall may return to South Africa and particularly the South Indian Ocean weeks 2-3. The latter may merge with the quasi-stationary enhanced Indonesian/Australian convection. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide, including official statements for tropical cyclones that may impact regions such as around Australia and Madagascar during the next several weeks.

Appendix

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

The following is a link to information about the stratosphere and other nice monitoring tools:

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from the following link:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

In addition to the subseasonal snr composite anomaly plots, we hope near real-time discussions with “weather maps” will 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! I plan on posting a discussion the weekend of 10-11 January 2009.

Ed Berry