The Dog is Back – No Cookbooks!!!

“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 now updated daily, centered on the date shown. Please see product descriptions. Part-1 of WB (2008), where the GWO is formally introduced, is in press for publication in MWR. There is a link in the Appendix to download the manuscript.

The general spatial pattern of global SSTs, tropical and extratropical, has not significantly changed for the past several weeks. Warmest ocean waters have shifted south of the equator in the warm pool region, where totals in excess of 30C exist just northeast of New Guinea. Widespread SSTs ~29C and greater extend from the TNWP into southwest Pacific Ocean. However, anomaly magnitudes are not that large. Finally, the strongest equatorial trade wind surge in at least 6 months from the Dateline to Indonesia is weakening. Negative anomalies across the central Pacific are ~1C. An upwelling oceanic Kelvin wave impacting the subsurface of the central and eastern equatorial Pacific Ocean during the next few months would be expected. See links below.

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

Similar to about a month ago, the WB (2008) measure of the GWO has decoupled from the tropical convective forcing (stated loosely for our purposes), including the MJO component. Keeping a complicated story simple, dynamical processes tied to meridional momentum transports (both hemispheres), positive surface torques (including from the above mentioned trade surge) and the baroclinic eddies greatly reduced anomalous zonal mean easterly wind flow across the subtropical atmospheres.

This is why the extratropical eddies have been northeast-southwest tilted (northwest-southeast Southern Hemisphere) in a base state favorable for anticyclonic wave breaking and anomalous midlatitude ridges for at least the past 2-3 weeks. Furthermore, anomalous zonal mean westerly wind flow has been shifted well poleward across the Northern Hemisphere, ~10-15m/s @ 200mb/60-70N. A rapid evolution through phases 8-1-2 of the WB (2008) GWO snr 250mb psi composite anomalies best describes the extratropical circulation through at least week-1.

Eastern Hemisphere tropical convective forcing remains intense, extending from Southeast Asia across the equator ~130E into the warm southwest Pacific Ocean. There has been a strong MJO component, recently projecting ~2 sigma in WH (2004) phase space. Through 30 October the latter was located in phase 5, phase 4 with the important interannual signal left in. Phase 5 of the WH (2004) 250mb snr composite psi anomaly plots is fairly representative of current tropical circulation anomalies.

While there continues to be a preference for zonally oriented Rossby wave energy dispersions (RWDs) given the GWO, the MJO component of the tropical forcing has been unquestionably impacting the global extratropics including the USA. For instance, per animations of upper tropospheric daily mean vector wind anomalies, ~22 October RWDs from the twin subtropical west Pacific Ocean cyclones contributed to west coast ridge amplification and baroclinic storm development on the Plains. There is actually a weak signal supporting this notion from phase 4 of the WH (2004) MJO snr 250mb composite psi anomaly plots.

Yes, on average midlatitude signals from tropical forcing are weak especially this time of year; however, individual cases can be/are exceptions. For instance, linked to GWO dynamics briefly addressed above, wind speed anomaly magnitudes associated with the MJO forced RWD heading toward the USA west coast 7-10 days ago were ~40-50m/s at 250mb. This is an example why daily monitoring is critical, and why looking for classic cookbook responses like “pineapple expresses” do not work most of the time in the real atmosphere (the Rottweiler is very angry!). Finally, there is also the issue that the WB (2008) measure of the GWO is a dynamical global index while tools such as the WH (2004) measure of the MJO are empirical and equatorially confined. The former is needed to more completely understand tropical-extratropical interactions, and our recent paper gives some attention to that matter.

Cutting to the chase, the MJO component has been propagating east ~5 deg long/day since roughly mid October. This movement is slowing, and the tropical convection with it has lost some intensity. Additionally, tied to the GWO, tropical convection has already been increasing across the Western Hemisphere. Animations of upper tropospheric daily mean vector wind anomalies present a strong signal of a RWD/baroclinic wave packet from a central Pacific Ocean anticyclone all the way into Europe. GWO processes like these should contribute to subtropical transition bringing the anticyclones (cyclones) into the Western Hemisphere (Eastern Hemisphere). However, I think it more probable that the subtropical anticyclones will be stronger than the cyclones, and the latter short-lived.

Updated through 28 October, the global frictional torque is ~minus 10 Hadleys, due to midlatitude frictional dissipation and weakening trades. Although this negative response is similar to around mid September, roughly 50 days ago, the physical processes responsible then and now are not. That said, per reasons discussed in WB (2008) and the current situation with the tropical convective forcing, both the GWO and the MJO should couple in ~octants 7-8-1 of phase space approximately mid-late November. In some sense, the global circulation at that time may be a superimposition of the circulation anomalies depicted by the corresponding GWO and MJO snr 250mb composite psi anomaly plots.

Again, timing is simply noise and my confidence is lowered because of seasonal cycle issues. Further, this is only “scientific speculation” until we develop better tools. All one can say physically is the following. As the tropical forcing shifts into the western Pacific Ocean during the next 1-2 weeks, a sequence of events involving first a positive global mountain torque followed by equatorward momentum transport would be probable. Subsequently, an extended North Pacific jet, then finally (in the GWO composite sense) a zonally oriented RWD/baroclinic wave packet collapsing the jet leading to a western USA trough.

However, I think this reasoning is scientifically defensible and provides additional predictive information to evaluate numerical models should they “catch on”. As discussed a week ago, the latter suggests more strong troughs to impact the western USA leading to an active storm track on the Plains weeks 3-4. A cold regime may follow during December focusing on the central states (while extending from perhaps the Pacific Northwest into the Great Lakes and northeast states).

In general, the character of the global circulation remains La-Nina. At some point during the upcoming boreal winter a quasi-stationary state residing in octants 3-5 of GWO phase space may evolve. Weather ramifications for all the above should be understood from the snr composites.

Internationally, intense thunderstorm activity should continue weeks 1-2 from particularly the TNWP/portions of Indonesia into the SPCZ. In fact, severe tropical thunderstorm flare-ups including cyclones are a concern on both sides of the equator. Locations impacted may include the Philippines/South China Sea and the Polynesian Islands. There are already Western Hemisphere flare-ups including increasing diurnal thunderstorm activity across tropical South America. Locations around the Americas including Brasil should see an increase in rainfall ~weeks 2-3 (maybe longer). Africa into the equatorial Indian Ocean are probable to be suppressed until ~ later week-2 and week-3. Regardless of the details, I would be surprised not to see much of the Indian Ocean into Indonesia strongly convectively active going into December.

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide. For instance, much of Western Europe has recently been active, and Arctic air is rapidly building from North America into Asia.

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 (2008)), 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

We hope additional overlapping seasonally varying global and zonal mean subseasonal composites for variables such as surface air temperature, precipitation, geopotential height, winds and streamfunction anomalies can be posted on the ESRL/PSD GSDM web site. Part-2 of our 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 complete discussion the weekend of 8-9 November.

Ed Berry

Update – Bear Atmosphere Stimulus???

“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

This discussion will be limited given time constraints. The 91-day signal to noise ratio (snr) anomaly composites are now updated daily, centered on the date shown. Please see product descriptions. Part-1 of WB (2008), where the GWO is formally introduced, is in press for publication in MWR. Please see link in Appendix.

SSTs have cooled across the equatorial Indian Ocean as a response to intense rainfall. Significant cooling has also been occurring in the region of the equatorial Dateline to Indonesia, as a result of a strong trade wind surge. For instance, the 29C isotherm has shifted back to ~160E. The latter may be the initiation of a coupled ocean-atmosphere response toward La-Nina, which has been the character of the global circulation for the past several weeks and longer. Stay tuned, and see links below.

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 large amplitude subseasonal event, the strongest since at least last May, involving multiple time scales is in progress. Since the start of this month, the WB (2008) measure of the GWO has done a good 2 sigma orbit in phase space, reaching octant 4 about a week ago. As I type the GWO (updated through 22 October) is collapsing toward octants 8-1. The WH (2004) measure of the MJO (through 23 October) has ~2 sigma projection in octant 4 of phase space. However, that projection increases to roughly 2.5 standard deviations in octant 3 retaining the ENSO signal (more realistic).

Per full disk satellite imagery and animations of upper tropospheric daily mean vector wind anomalies, phases 3-4 of both the GWO and MJO snr composite 250mb psi anomalies nicely depict the global circulation. There is strong meridional symmetry of zonal mean zonal wind anomalies, including anomalous midlatitude ridges.

The eastward shift of tropical convection from the Indian Ocean into Indonesia, working dynamically with coupled processes involving the surface torques, poleward AAM transports and extratropical eddies have attempted to shift the atmosphere away from the La-Nina attractor. In fact, global relative AAM recently spiked to a slightly positive anomaly. However, there has been a greater removal of anomalous zonal mean easterly wind flow from the subtropical atmospheres than actually adding westerlies. Having my reasons, analogous to recent failed financial stimuli to save the on-going collapsing global stock markets, the same may be true for the atmosphere.

There is no change to my speculative outlooks from past discussions. My confidence would be higher if I was doing this writing a month from now given seasonal cycle issues. For example, meridionally directed Rossby wave energy dispersions (RWDs) forced by west Pacific Ocean tropical convection is more likely to impact North America during boreal winter than autumn.

Observational evidence suggests a quasi-stationary component of the tropical forcing (~90-130E per OLR time sections)/global circulation anomalies may be emerging. However, going along with the GWO (keeping in mind rapid variations), I do think it is probable there will a signal of tropical forcing propagating first into the west central Pacific, then Western Hemisphere by roughly week-3, perhaps sooner (noise understood). Hence an evolution of anomalies shown by phases 3-5 of both the MJO and GWO composites of snr 250mb psi anomalies is probable weeks 1-2. A “jump” to phases 7-8-1 circulation anomalies shown by particularly the GWO composites may be reasonable weeks 3-4. The latter suggests anomalously strong troughs to impact the western USA leading to an active southwest flow storm track on the Plains. A cold regime, characteristic of ~GWO phase 3 focusing on the middle of the country, may evolve during December.

Internationally, intense to severe thunderstorm clusters will continue to impact the Bay of Bengal into Indonesia week-1, shifting slightly east week-2. Locations from Southeast Asia through the Philippines as well as portions of the southwest Pacific Ocean may experience intense rainfall weeks 2-3. The tropical cyclone hazard is unclear; however, I think it is unlikely to observe a westerly wind event of the same magnitude as the current trade surge west of the Dateline. The tropical Americas including portions of Brasil may experience a significant increase in rainfall perhaps by late week-2.

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide. There has been an increase during the last week, including locations such as Honduras and Morocco.

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 (2008)), 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

We hope additional overlapping seasonally varying global and zonal mean subseasonal composites for variables such as surface air temperature, precipitation, geopotential height, winds and streamfunction anomalies can be posted on the ESRL/PSD GSDM web site. Part-2 of our 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 complete discussion the weekend of 31 October-2 November.

Ed Berry

Atmosphere Spiraling into Recession?

“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 now updated daily, centered on the date shown. Please see product descriptions. Part-1 of WB (2008), where the GWO is formally introduced, is in press for publication in MWR. Please see link in Appendix.

Responding to anomalous convection, SSTs have cooled across portions of the equatorial Indian Ocean. Anomaly magnitudes are loosely slightly under 0C with totals less than 28C. However, a well defined axis of positive SST anomalies, ~1-2C, extends from the Arabian Sea east-southeast to around New Guinea. Shifting south with the seasonal cycle, the warmest SSTs globally are centered on 0-5S/150-160E, with totals in excess of 30C. Our anomalous horseshoes of SST warmth and coolness continue to radiate from the TNWP and equatorial Dateline regions, respectably, projecting on what some consider being a negative phase of the PDO. Links below provide additional SST details.

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

Weather-climate signals have become significant, and the global circulation has evolved to exhibiting a strong La-Nina behavior. I can only give a few dynamical reasons in the interest of brevity. First, I will address this situation from the “GWO perspective”, and then bring in the roles of the tropical convective forcing.

From an AAM budget viewpoint, there apparently exists a balance of forces wanting to add and remove global and zonal mean wind flow anomalies in what may become a quasi-stationary La-Nina situation. For instance, around 25S and 30N zonal mean negative AAM anomalies approaching 2 atmospheric momentum units (AMUs; through 16 October) flanked by somewhat weaker positive anomalies on their poleward flanks are present. This means there are poleward shifted zonal mean jets in both hemispheres in a circulation base state favorable of anomalous midlatitude ridges and anticyclonic wave breaking (AWB) baroclinic development.

When viewing animations of daily mean upper tropospheric vector wind anomalies, for at least the past week the synoptic eddies have generally been NE-SW (NW-SE Southern Hemisphere) tilted. This orientation has been favorable for fluxing AAM out of the subtropical into the midlatitude atmospheres. First across the Southern Hemisphere earlier this month and then over the Northern Hemisphere during the last 7-10 days, zonal mean subtropical AAM sinks and midlatitude sources have been well pronounced. Finally, having a global signal of ~plus 10 Hadleys, a well defined interhemispheric dipole of positive (negative) zonal mean frictional torque in the subtropical (midlatitude) atmospheres has been present for at least the past 10 days. The latter suggests anomalous surface easterlies in the subtropics with frictional dissipation in the storm track regions.

Overall, global relative AAM minus the QBO signal may have (for now) reached an equilibrium of ~1 standard deviation below the R1 data climatology due to offsetting dynamical feedback processes trying to keep the atmosphere rotating at the same rate as the earth. The combination of the surface torques and AAM transports has spiked the calculated tendency to ~plus 30 Hadleys. The computed AAM tendency, one of the components of the WB (2008) measure of the GWO, has peaked to ~plus 40 Hadleys. However, there may be some averaging issues for the latter. In any case, the GWO has orbited to at least a 2 sigma projection in octant 4 of phase space. I do think we are seeing another fast GWO variation involving phases 4-5 and 8-1, in the presence of the phase vector orbiting around octant 3 (La-Nina).

Phase 3 of the WB (2008) GWO 250mb snr streamfunction composite anomaly plots best represents the global atmosphere. Similar to what was often observed during JFM 2008, remarkable for October, there is currently a strong positive phase of the Branstator (2002) circumglobal teleconnection. The latter includes my familiar statement of interhemispheric meridional symmetry of zonally symmetric zonal mean zonal wind flow anomalies.

Full disk satellite imagery and other tools show strong Indian Ocean tropical convective forcing, centered ~0/80-90E. Latest three-day averaged OLRA per BMRC have been well under minus 50 W/m**2 for this region of severe tropical rainfall. Tropical cyclones (loosely) have been spinning off across the South Indian Ocean and Arabian Sea. Animations of upper tropospheric daily mean vector wind anomalies show subtropical transition to western Indian Ocean (western Pacific Ocean) anticyclones (cyclones). The WH (2004) MJO measure gives a slightly greater than 1 standard deviation projection in octant 3 of phase space, and a more representative strong 2 sigma Indian Ocean signal leaving the base state in. For various reasons, other flare-ups of intense thunderstorm clusters continue across the global tropics. Phase 3 of the 250mb snr streamfunction composite anomalies done on the WH (2004) measure of the MJO best represents the current tropical circulation.

Summarizing, with tropical-extratropical coupling, the GWO is still “calling the shots” and the MJO component is “going along for the ride”. Rossby wave energy dispersions (RWDs) continue to be zonally oriented, suggestive of dynamical processes involving the mountains (not discussed today) and AAM transports. Part of the positive global frictional torque is due to a strong trade wind surge (~10m/s anomalies) from the equatorial Dateline to roughly Indonesia. These surges have been stronger than any westerly wind events since at least late May 2008. While monitoring is so critical, I think this pattern will continue for the next few months, possibly longer. I have my reasons for thinking that at least the equatorial central Pacific Ocean SST anomalies are going to respond to the atmosphere (cool). Unless there are any “huge changes”, having periods of constructive and destructive interference, the global circulation may exhibit La-Nina characteristics well into 2009. The intensity is unclear.

Worth repeating from my last posting, regardless of what happens, any statement about the outcome of the 2008-09 boreal cold season must consider roles of subseasonal variability and global tropical SSTs. “ENSO neutral” is a completely inaccurate description about the current weather-climate situation, and may be “until further notice”.

Like a week ago, I feel fairly confident where atmosphere will go during the next several weeks, and there is little change in my thinking. My feeling is that the Eastern Hemisphere tropical convective forcing will shift east to roughly the 29C SST isotherm, meaning ~150-160E depending on the impacts from the current trade wind surge. Per above, there is already a well defined positive anomaly SST perturbation east and north of the tropical forcing. Using the MJO time scale of ~3-4 degrees of longitude shift per day, by ~week 3 rainfall may be particularly intense from Southeast Asia into the west central Pacific Ocean. Hence a loose evolution through a “superposition” shown by the snr composite anomalies for 250mb streamfunction and 2m air temperature for GWO and MJO phases 3-5 appears probable during the ~next 1-3 weeks. This suggests general ridge conditions shifting into the western states and troughs for the central and eastern USA.

I also think another “GWO/MJO 7-8-1” transition depicted by the snr plots roughly weeks 4-5 may be in the offing. Again, timing is white noise. Per above, it is looking more probable that should this kind of transition occur, it will be a perturbation that destructively interferes with a La-Nina base state. Weather ramifications may include a stormy period focusing on the western and central USA, perhaps including intense winter precipitation and thunderstorms, possibly making travel difficult around Thanksgiving. At this point I will also offer that a December rendition of the global circulation depicted by the GWO phase 3-5 snr 250mb composite streamfunction anomaly plots may increase the probability of anomalous cold focusing on the north central USA.

The same issues for this boreal winter remain, and "outlooks/speculations" per my past discussions are unchanged. The anomalously warm west central Pacific Ocean always may be the “bail out” from keeping the global atmosphere spiraling “too low (AAM)” in GWO phase space. Our nemesis of 2 regions of tropical convective forcing may return, and/or episodic intense equatorial west Pacific Ocean westerly wind bursts may start. However, a tilt toward a La-Nina seasonal base state is appearing more probable.

Internationally, during the next 1-3 weeks, per above, intense to severe tropical thunderstorm activity is probable to shift east-northeast from the central Indian Ocean through Indonesia, Southeast Asia, then into the northwest and west central Pacific Ocean. Tropical cyclones may be left in the wake, particularly the Bay of Bengal ~week-2 then the TNWP (possibly impacting the Philippines) week-3. The southwest Pacific Ocean along the SPCZ may see enhanced convection weeks 3-4. The Western Hemisphere should be relatively quiet weeks 1-2. Hybrids are always a concern in any prone basin, especially in a base state that favors AWB.

Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide.

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 (2008)), 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

Overlapping seasonally varying subseasonal composites for variables such as surface temperature, precipitation, geopotential height and streamfunction anomalies are planned on being posted on the ESRL/PSD GSDM web site and presented in part-2 of our paper. 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! My next complete discussion is not likely until around the weekend of 31 October, 1-2 November. I may be able to post a short update ~24 October.

Ed Berry

Global Circulation Going Down with the Markets - Part Deux

“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 now updated daily, centered on the date shown. Please see product descriptions. Part-1 of WB (2008), where the GWO is formally introduced, has been accepted for publication in MWR. Please see link in Appendix.

SSTs have continued to warm across the Indian Ocean, with recent daily totals ~30C north of the equator around 60E. Anomalies, significant for these waters, are at least plus 0.5-1C. Large portions of the Arabian Sea and regions of the Bay of Bengal have anomaly magnitudes greater than 1C. The west central and southwest Pacific Ocean are the warmest globally, with totals ~30-31C, but only having anomalies ~0.5-1C. The warm Indian Ocean will support further intensification of tropical convection (discussed below) during the next few weeks. The relatively warm west central Pacific Ocean increases the odds for tropical forcing to propagate east into the warm pool region this coming boreal winter. Links below provide additional SST details.

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 characteristics of the global circulation have become solidly La-Nina. Global relative AAM, updated through 9 October removing the QBO signal, is nearly 2 standard deviations below the R1 data climatology. This is the lowest value since boreal spring. Zonal mean AAM anomalies are ~minus 2 AMUs near 25S and ~minus 1 AMU around 25N. The latter translates to 200mb zonal mean easterly wind flow anomalies of ~10m/s (~5m/s) ~25S (~25N). Relatively weak zonal mean westerly wind flow anomalies are on the poleward flanks, once again suggestive of anomalous midlatitude ridges and poleward shifted zonal mean polar jet streams.

Zonal mean AAM sinks are pronounced ~25S and 35N (keep in mind boreal autumn and austral spring issues) with flux convergence of AAM transport near 45N and 50S (latter shifting poleward). This is an important characteristic of a low AAM base state (GWO phases 2-3), having midlatitude synoptic eddies northeast-southwest tilted (southeast-northwest tilted Southern Hemisphere), favoring anticyclonic wave breaking. For instance, roughly a week ago, after a GWO phases 8-1 transition, a cyclonically wave breaking trough amplified into the western USA. As I type, the current western states mid/upper tropospheric trough/closed low is undergoing anticyclonic wave breaking baroclinic development. This kind of dynamical behavior is best seen in isentropic potential vorticity (IPV) space.

Full disk satellite imagery show tropical convective forcing intensifying across much of the Indian Ocean, centered just north of the equator ~80E. Other enhancement persists from the Americas into equatorial Africa. The meridionally oriented interhemispheric Rossby wave energy dispersions (RWDs) that were across the Western Hemisphere (see phases 8-1 of the MJO 250mb snr psi composite anomaly plots) about a week ago are currently propagating into the Eastern Hemisphere. A response is that upper tropospheric divergence is increasing over the anomalously warm Indian Ocean leading to an enhancement of tropical convection. This chain of events is not unusual when a MJO component re-emerges into the Indian Ocean, and the extratropics are generally involved.

Removing the interannual component, the WH (2004) measure of the MJO (updated through 8 October) only shows a very weak projection in octant 2 of phase space. However, that projection increases to roughly 1.5 standard deviations in the same octant with the base state left in (used for this discussion). The WB (2008) GWO measure also shows approximately a 1.5 sigma projection in octants 2-3 of phase space. Hence, based on these measures, the former empirical/equatorially confined and the latter global/dynamical, the tropics and extratropics are becoming coupled. This situation has been expected to occur. MJO phase 2 of the 250mb snr psi composite anomaly plot best represents the current tropical circulation anomalies as does GWO phase 2 for the extratropics.

Summing up, the issues discussed in my 4 October posting remain and will not be repeated here. Since ~10 September the dynamics explained by the WB (2008) measure of the GWO have been dominating the global circulation. The RWD cited above was a response from the MJO component. Animations of daily mean anomalies of upper tropospheric vector wind currently show zonally oriented chains of midlatitude RWDs while a transition to twin tropical anticyclones (cyclones) occurs across the Indian Ocean (west Pacific Ocean). An important monitoring concern is how much SST cooling will occur in the region of the equatorial Dateline forced by enhanced trades over the next few weeks. Any statement about the outcome of the 2008-09 boreal cold season must consider roles of subseasonal atmospheric variability and global tropical SSTs, such as the above (yes, insert the angry Rottweiler!). I do not think statements like “ENSO-neutral conditions are expected to continue into early 2009” serves weather sensitive users well.

I feel fairly confident where the global atmosphere will go during the next several weeks; however, that is somewhat difficult to illustrate in the format of these discussions (and timing is white noise). Currently there is some interhemispheric meridional symmetry of zonally symmetric zonal mean wind anomalies, typical of a positive phase of the Branstator (2002) circumglobal teleconnection. GWO phases 2-3 of the 250mb snr psi composite anomaly plots illustrate that response. While a slow evolution shown by phases 3-5 of the 250mb snr psi composite anomaly plots for both GWO and MJO is probable during the next 2-4 weeks, faster embedded GWO variations tied to the surface torques are likely. For instance, an extended North Pacific Ocean jet outrunning the Eastern Hemisphere tropical forcing may occur during week-2, possibly collapsing into the western USA trough. Weather outcomes should be understood.

In the longer term, perhaps early November to around Thanksgiving, anomalous moist tropical convective forcing may shift into the west central Pacific Ocean leading to another transition shown by MJO/GWO phases 7-8-1 of the 250mb snr psi composite anomalies (see the corresponding 2m air temperature anomaly plots). At that point, this behavior may be a perturbation upon a La-Nina base state. Weather ramifications during that time may include another stormy period focusing on the western and central USA.

There is no change to my thoughts for boreal winter. The anomalously warm west central Pacific Ocean always concerns me, and that may be the “bail out” from keeping the global atmosphere spiraling “too low (AAM)” in GWO phase space. Stay tuned to see if our nemesis of 2 regions of tropical convective forcing returns and/or robust equatorial west Pacific Ocean westerly wind bursts starts to occur.

Internationally, while tropical forcing including the risk of cyclones winds down weeks 1-2 for the Western Hemisphere (hybrids understood), intense to severe thunderstorm activity is likely to increase/remain anomalously intense across Africa and the equatorial Indian Ocean this upcoming week. During weeks 2-3 locations throughout much of the central and eastern Indian Ocean, Indonesia and Southeast Asia may be strongly impacted with enhanced rainfall. Furthermore, tropical cyclogenesis across the Bay of Bengal may be greater than climatology during the next few weeks. High impact weather due to tropical convection may focus on the TNWP into the west central Pacific Ocean weeks 3-4. Please see the latest official tropical cyclone forecasts for all basins.

I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide. For instance, our current base state favors a poleward shifted storm track across the North Atlantic Ocean which may adversely impact much of Europe during the next few 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 (2008)), has been accepted for publication MWR. A pdf of the revised and accepted version can be downloaded from the
following link:

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

Overlapping seasonally varying subseasonal composites for variables such as surface temperature, precipitation, geopotential height and streamfunction anomalies are planned on being posted on the ESRL/PSD GSDM web site and presented in part-2 of our paper. 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 should be able to do a discussion next weekend, ~18-19 October.

Ed Berry