Atmospheric Insights

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

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)

Full disk satellite imagery shows multiple regions of enhanced tropical convection. Loosely, these are centered from the equatorial western Indian Ocean into the Eastern Hemisphere monsoon systems, the west central Pacific and in the region of the Americas. Hovmoller plots and other diagnostic tools show there has been a slow eastward shift of tropical convective forcing since early May. Per WH (2004) phase space plots, a MJO component of this forcing is present, currently in octant 8 ("Western Hemisphere and Africa").

The extratropics have contributed to the eastward shift of tropical convective forcing. Included are north-south mountain massifs, having broadly positive global mountain torque events of ~20 Hadleys late May, mid-June and most recently. The latter involved the Southern Hemisphere mountain ranges such as the Andes and those over Antarctica. The tropical forcing and stochastic mountain torque events are some of the subseasonal dynamics captured by the WB (2007, 08) GWO.

Complicated interactions of processes briefly mentioned above have worked to add westerly wind flow to the global atmosphere. For example, zonal mean westerly wind flow anomalies of ~5m/s have shifted off the equator into the Northern Hemisphere subtropical atmosphere. There was also a (very) slight transient reversal of upper tropospheric tropical circulation anomalies across the Eastern Hemisphere a few days ago (~24 June), with twin cyclones trying to evolve in the region of the Indian Ocean along with downstream anticyclones. Hence the WB (2007, 08) GWO orbited in phase space to octant 5 on 22 June, before collapsing. Including the westerly QBO phase of the stratosphere, global relative AAM through 26 June was near the R1 data climatology. However, I do expect to see relative AAM decrease (abruptly like the USA stock market???) during the next few weeks.

There is evidence of some tropical-extratropical coupling returning. The WH (2004) MJO and WB (2007, 08) GWO plots are starting to line up in phase space; ~ octants 8-1-2-3 are probable during the next few weeks. Support for this notion includes a negative global frictional torque (~10 Hadleys – GWO component) and a few predictions (ex., POAMA and ECMWF) of the WH (2004) RMM index to orbit to phase 3 by week-3. Physically this means a return to a La-Nina base state and/or a re-enforcement of a stationary low AAM regime that has been present for at least the past year. Seasonal implications are still unclear. The point is that the atmosphere is orbiting in phase space around what may still be the “La-Nina attractor”. This evolution is the foundation for subseasonal predictive information offered below.

In my last posting I suggested a western/northwestern USA trough for the upcoming week. Instead, the wicked ridge (from Hell) of the western USA is returning. Based on subseasonal composites currently being developed, similar to July 2007, anomalous summertime ridge conditions for the western states are probable during phases 3-4 of the GWO. Like that observed during boreal winter 2007-08, these same phases of the GWO favor a western USA trough during the cold season given wavelength considerations (still the season of the witch leading to the wicked ridge of the west?). Based on these composites and rigorous daily monitoring, I had indications of my poor assessment 2 days later. A dedicated web page effort where these subseasonal composites and other tools are available would have greatly facilitated an update.

As all models now show (the GFS has been playing catch-up), an amplified western USA ridge and eastern states trough is likely week-1. I do think this ridge will expand into the central states and Deep South ~week 2, before possibly re-amplifying west of Continental Divide weeks 3-4 allowing a trough in the region of the Mississippi Valley. Thus intense western heat may briefly expand into portions of the eastern USA week-2 after a cool week-1. There will be an active MCS storm track along the “southern edge of the westerlies” focused at times on the mid and upper Mississippi Valley states ~weeks 2-3. The "Desert Southwest monsoon" may get off to a robust start during the next couple of weeks, much like climatology suggests. Other ramifications should be understood.

Intense to severe tropical thunderstorm activity is probable to increase from the Indian Ocean into the monsoon and frontal rain band systems of India and Asia weeks 2-3 while the west and northwest Pacific Ocean is sporadic. The East Pacific Ocean tropical cyclone hazard should wane during week-2. I would have a greater concern for cyclones across the tropical Atlantic Ocean basin weeks 1-2 if it were August-September. Please see the latest official tropical cyclone forecasts for all basins.

Other severe/high impact weather continues internationally. I trust the expertise of the appropriate weather centers to alert the public of additional weather hazards worldwide.

Appendix

An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at

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

This phase plot is being re-done, as is the web site. Stay tuned. We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous to the WH (2004) “convention”. In addition, the GWO plot does not have the ENSO signal removed.

Please see the revised description of the GSDM per above link -- which will be revised again (work in progress)!!!. Also, I encourage the readers to study the annotated MJO and GWO phase space plots to help relate the global variations explained by those techniques to “weather”.

Links to CPC and PSD ENSO discussions:

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

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

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, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. This web page effort would hopefully include an objective predictive scheme for the GWO, including hindcasts.

The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, the first of a two-part paper has been submitted to MWR where WB formally introduces the GWO. A pdf version can be downloaded from the following link

http://www.cdc.noaa.gov/map/clim/wb08_final.pdf

Overlapping seasonally varying subseasonal composites for variables such as surface temperatures and streamfunction anomalies are planned on being posted on the web site mentioned above 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. Relying on the numerical models alone is a cookbook!

Given shift work and travel, updates are extremely difficult. I hope to post another discussion the weekend of 4-6 July.

Ed Berry

Friday, June 20, 2008

ENSO Neutral with Lingering La-Nina Circulation?

“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”

Global tropical SST anomalies are relatively weak. Exceptions include the cool anomalies in the region of the equatorial date line, and warmth across the equatorial East Pacific as well as the central and eastern tropical Atlantic Oceans (from arguably an Atlantic El-Nino that matured during boreal spring). Anomaly magnitudes for the latter are ~1-2C. Warmest SSTs are still from the central Indian Ocean into the tropical Northwest Pacific basin with totals ~28-30C. Outside the tropics, the warm and cool horseshoe anomalies across the entire Pacific Ocean basin having the spatial pattern typical of El-Viejo remain well defined (I am well aware of the PDO “fans”).

Subsurface anomalies and everything else that can be argued about all understood, I offer the following. Remembering that ENSO is only a component of an interannual signal involving the global coupled ocean-land-atmosphere dynamical system, I think it is more likely to see some rejuvenation La-Nina than an evolution toward El-Nino going into boreal winter 2008-09. However, uncertainty is very high. Stay tuned. The following are links to additional SST related information.

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

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

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).

In general, subseasonal signals as given by the WH (2004) MJO and WB (2007, 08) GWO phase space plots are weak. In fact, the WH (2004) projection is near zero, even with the interannual component left in. While generally true that subseasonal signals are currently fairly weak, there is still information to be gained from careful thought and diagnostic monitoring, as well as having an understanding of how the phase space plots are derived. Also, I disagree with any notions (official or otherwise) that useful predictive probability statements of any possible high impact weather (etc.) cannot be made in these “weak” situations (my Rottweiler is growling -- wanted to work him in!).

Full disk satellite imagery and other tools loosely suggest 2 regions of enhanced tropical convective forcing across the Eastern Hemisphere. One region is centered on the Indian Ocean from the equator into the monsoon systems with the other focused on the west central Pacific Ocean ~0/145E. The former has been slowly weakening with the latter intensifying, including Typhoon Fengshen hammering the Philippines. West Pacific tropical cyclone development was offered as a possibility in my posting about 2 weeks ago.

I feel comfortable defending the notion that Rossby wave energy dispersions (RWDs) tied to the Indian Ocean forcing interacting with the extratropics (and vice-versa) led to the west central Pacific Ocean signal. For example, there was enhancement of the upper tropospheric twin tropical cyclones near the date line leading to intensified divergence across the west Pacific Ocean. In addition, equatorial westerly wind anomalies of ~25m/s at times have also occurred with the twin cyclones. These westerly anomalies are shifting poleward (in a manner too complicated to discuss here) and are/will impact the extratropics in the near future (more said below).

Global relative AAM (only updated through 16 June; data issues again) remains a good 1 sigma below the R1 data climatology. A recent spike in the global mountain torque (~plus 25 Hadleys) having the largest contribution from East Asia is why the WB (2007, 08) GWO shows a circuit toward octal 5. This positive mountain torque event also contributed to the intensification of the west central Pacific Ocean tropical convection discussed above (and added westerly wind flow anomalies to the atmosphere). Animations of mean sea-level pressure anomalies suggest this component of the global mountain torque is decreasing.

Continuing, while the recent computed AAM tendency may be relatively large (3-day average), the calculated AAM tendency is near zero. Reasons include a negative Coriolis torque and fairly weak zonal mean AAM transports. In any case, the WB (2007, 08) GWO is more likely shifted toward octant 3 but having fairly fast orbits in phase space.

As discussed above, there is evidence of westerly wind flow anomalies shifting into the subtropical atmospheres, flanked by poleward propagation of zonal mean easterly wind flow anomalies through the midlatitudes. Thus animations of daily mean upper tropospheric vector wind anomalies do suggest a return of a circumglobal teleconnection of midlatitude ridges. Midlatitude RWDs are generally zonally oriented, anchored by twin tropical/subtropical anticyclones in the region of the Indian Ocean and cyclones around the date line. Overall, with robust zonal mean westerly wind flow anomalies present at the higher latitudes (~15-20m/s at 200mb ~60S), once again there is some meridional symmetry of zonally symmetric zonal mean circulation anomalies.

So, where does the atmosphere go from here? First, I think there will be a tropical convective forcing signal propagating fairly quickly through the Western Hemisphere during the next 1-3 weeks. In fact, a zonal wave number 2 structure of tropical circulation anomalies may again emerge. The Eastern Hemisphere monsoon systems may have a break, but perhaps only briefly for various reasons.

The RWDs are one of the mechanisms bringing anomalous subtropical westerly wind flow into the midlatitudes. Cutting to the chase for the PNA sector (remembering boreal summer), a strengthening of the jet across the North Pacific Ocean collapsing into an anomalous northwestern/western USA trough by around week-2 I think is probable. At some point ~weeks 3-4 that trough (made up of synoptic events) is likely to shift east. Numerical models have been trending toward the latter for week-2.

A source of uncertainty but critical for the severe storms/flood ravaged areas centered on Iowa is how far south will the jet extend going into July? My own feeling is enough for rounds of intense-severe MCS activity starting week-2 (week-1 understood). Other locations across the central Plains into the Mississippi Valley are probable for at least climatology MCS activity. Areas that have been dry will hopefully receive beneficial rainfall. While portions of the northwestern states tilt toward cooler than normal, intense heat initially across the Desert Southwest and southern Plains may expand into the Deep South, Ohio Valley and portions of the East Coast weeks 2-4.

Per above, the monsoon systems of India and Southeast Asia may have lessened rainfall intensity ~weeks 1-2 compared to the last couple weeks while the west central and northwest Pacific Ocean remains active at least week-1. Intense to severe thunderstorm activity including additional tropical cyclones is a concern for the latter including the Philippines. By weeks 2-3 rainfall may become quite intense from the East Pacific Ocean ITCZ all the way into equatorial Africa. Please see the latest statements from the JTWC and TPC for tropical cyclone concerns. There may be an increased risk for tropical cyclone development across the East Pacific starting week2 and perhaps the Atlantic basin by weeks 3-4.

Other severe/high impact weather continues internationally. I trust the expertise of the appropriate weather centers to alert the public of additional weather hazards worldwide.

Appendix

An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at

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

Please see the revised description of the GSDM per above link. Also, I encourage the readers to study the annotated MJO and GWO phase space plots to help relate the global variations explained by those techniques to “weather”.

Links to CPC and PSD ENSO discussions:

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, the first of a two-part paper has been submitted to MWR where WB formally introduces the GWO, including the "correct" rendition of the GWO phase space plot. A pdf version can be downloaded from the following link

http://www.cdc.noaa.gov/map/clim/wb08_final.pdf

Overlapping seasonally varying subseasonal composites for variables such as surface temperatures and streamfunction anomalies are planned on being presented in part-2. 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 frame work to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process. Relying on the numerical models alone is a cookbook!

Given shift work and travel, updates are extremely difficult. I hope to post another discussion the weekend of 28-29 June.

Ed Berry

Saturday, June 14, 2008

Update on Postponed

As typed a week ago, my schedule precludes me from posting a complete discussion today. I will try to do that next weekend (21-22 June).

Briefly, the return of tropical convective forcing to the Eastern Hemisphere has rejuvenated our La-Nina base state (as was discussed past couple of postings). Global relative AAM updated through 12 June was ~1 sigma below the R1 data climatology. Full-disk satellite imagery shows intense-severe tropical thunderstorm activity focused on the Bay of Bengal, enhancing the Indian and Asian monsoon systems, with arguably a separate area concentrated ~5N/155E.

There is some possibility we may be seeing (the return of Nemesis?) 2 regions of tropical forcing. This spatial pattern is why the recent projection onto the WH (2004) MJO index has weakened. Interactions with the extratropics have contributed to this possible west central Pacific Ocean signal. My suspicion is there will be a signal having a MJO component that shifts into the tropical northwest Pacific Ocean and Western Hemisphere during the next 2-4 weeks.

Interspersed with MJOs #5 and 6, since ~mid April there have loosely been ~20-30 day variations of clustered positive global mountain torque events (roughly 15-20 Hadleys), with the most recent around 1 June. These have contributed to GWO circuits of varying amplitude. Through 12 June the GWO had orbited back down to octal 2 in phase space. While there are mixed signals between the tropics and extratropics, strong interactions explained by the dynamics of the GWO are occurring.

I feel quite comfortable (all things considered) from animations and other tools about where the global circulation is at including zonal mean to regional scale linkages. For instance, the large anomalous upper tropospheric cyclonic gyre ~30N/160W is linked to RWDs involving tropical-extratropical interactions. As the Eastern Hemisphere tropical forcing shifts east, for this time of year the North Pacific Ocean jet may extend forcing the anomalous gyre at least into the USA Pacific Northwest during weeks 2-3. The GWO would likely orbit to ~phase 5 before collapsing. Stay tuned.

The flood ravaged Upper Mississippi Valley (Revelation 2?) should get a respite from the intense rain and severe local storms week-1 while portions of the dry Southern Plains receive needed rainfall. However, intense-severe MCS activity appears probable to return to Northern Plains and Upper Mississippi Valley starting week-2 and perhaps especially weeks 3-4. After anomalously cool temperature conditions weeks 1-2 for portions of the Northern Plains into the eastern states, that situation may reverse weeks 3-4 with the hottest temperatures from possibly the Southern Plains into the Ohio Valley. Additional information is available from the following links.

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

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

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).

Appendix

An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at

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

Links to CPC and PSD ENSO discussions:

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

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

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

The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, a two-part paper is in ACTIVE preparation by WB that will formally introduce the GWO along with subseasonal composites for variables such as surface temperatures. In fact, part-1 was submitted this week, and maybe we can provide a pdf version on-line sometime soon. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships.

Given shift work and travel, updates are extremely difficult. I am planning on posting a discussion next weekend, 21-22 June.

Ed Berry

Saturday, June 07, 2008

MJO # 6 (not 666) -- A Witch Doctor?

There is little overall change in the spatial pattern of global SSTs since my last discussion. Anomalous horseshoes of warmth and coolness remain across the Pacific Ocean basin, particularly the Northern Hemisphere. In fact, SST totals greater than 27C extend to 20N at the date line. Other details can be viewed from the links below.

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

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

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).

There are a couple of observations I would like to share. First, per 5-day averaged TAO buoy data, equatorial subsurface anomalies are currently nearly opposite (through 6 June) compared to a year ago. That is, while the equatorial Pacific Ocean thermocline was relatively shallow a year ago, the opposite is now the case. Multiple MJO events since a year ago have contributed, leading to the ~1-3C anomalous warmth from roughly 200m depth west of the date line to 50m deep west of South America. Does this support the notion of transitioning to an equatorial Pacific Ocean warm event?

Continuing, as shown in the SSTA Hovmoller plot per following link,

there has been an approximate biennial character to warm and cold events since 2001-02. For example, note the periodicity of the ~1.5C anomalous warmth in relation to the date line.

However, that behavior appears to have changed since early 2007. Tied to the latest basin wide cooling, the above average warm pool SSTs have shifted to west of 140E on the equator. There are numerous other points that can be raised. Cutting to the chase, based on diagnostic monitoring utilizing various tools, a lot of work involving the coupled ocean-land-atmosphere dynamical system is going to have to be done to shift anomalously warm SSTs into the west central Pacific Ocean by boreal autumn. In the presence of extreme uncertainty (recall my posting last week), a “tilt” toward La-Nina may continue into 2009 (as part of the interannual component of the weather-climate system). Stay tuned.

Full disk satellite imagery shows intense to severe tropical thunderstorm activity extending from the Arabian Sea east-southeast into the extreme west central Pacific Ocean. Tropical rainfall has become generally sporadic elsewhere. The core of what is MJO #6 (since ~October 2007) is ~5-10N/100E, and is not only enhancing the monsoon systems, but also frontal activity across southeast China and eastern Australia. Water vapor imagery shows the polar and subtropical jets extending from this Eastern Hemisphere tropical convection leading to a central Pacific Ocean ridge and another one of those troughs across the western USA (more said below).

Updated through 6 June, WH (2004) phase space plots, particularly with the interannual component left in, indicate a nearly 2 standard deviation MJO projection in phase 3. This coherent evolution of MJO #6 was not captured very well by most statistical and dynamical predictive schemes. There are still predictions of quickly decaying this event, and I do not agree with that. Based on some thoughts of coupled dynamics involving the earth-atmosphere AAM budget, discussion was offered a week-ago that the tropical forcing would remain intact taking on the west-northwest to east southeast orientation across the Eastern Hemisphere discussed above. Those same processes led to a rapid increase of the surface trades (~5-10m/s anomalies) across the central and western Pacific Ocean (was expected), diminishing the tropical cyclone risk in that region. I did not offer a good statement of a decreased northwest Pacific Ocean tropical cyclone hazard a week ago.

I feel quite comfortable where I think the coupled global weather-climate system is at, and where it may be going. Keeping in mind seasonal cycle issues (boreal summer, austral winter), meridional symmetry of zonally symmetric zonal mean circulation anomalies continues. There is strong tropical-extratropical coupling leading now to a Branstator (2002) circumglobal teleconnection of midlatitude ridges. Some of the details of this situation were discussed last week. Even though the WB (2007, 08) GWO projection may appear weak, updated through 5 June there is still an orbit nearly in phase 3, and the above is consistent with a La-Nina base state. As stated previously, this type of circulation response to dynamical processes involving tropical convective forcing and midlatitude mountains has been observed frequently since January 2008 (“the season of the witch”).

Through 5 June, global relative AAM is ~minus 1 standard deviation below the R1 data climatology, with a near zero tendency. There are also relatively weak global signals of the surface torques and zonal mean AAM transports (for now). Hence why the WB (2007, 08) GWO projection is not that robust. However, the latter is a dynamical measure of the global circulation meaning that is it important to pay attention to its evolution. During the last couple of weeks there has been a clustered positive global mountain torque event peaking around 15 Hadleys just before 1 June. That has contributed to the most recent circuit in the WB (2007, 08) GWO phase space centered on octant 3, and a regional response of another anomalously strong North Pacific Ocean jet. Tied to this global mountain torque episode as well as processes linked to the MJO, poleward propagation of zonal mean easterly wind flow anomalies in the subtropical atmospheres (~10-20 N/S) and westerly anomalies in the midlatitudes (~30-40 N/S) has been occurring this past week.

Animations of upper tropospheric daily mean vector wind anomalies continue to present the expected and improving circulation response consistent with the WB (2007, 08) GWO. Twin upper tropospheric tropical anticyclones are becoming established the Indian Ocean with cyclones in the region of the date line. Equatorial westerly wind flow anomalies (~25m/s at 150mb) are increasing east of the date line, part of the baroclinic response linked to the strengthening trades. Rossby wave energy dispersions (RWDs) continue strongly zonally oriented across the midlatitudes, leading to another western USA trough as I type.

I think the Eastern Hemisphere tropical convective forcing will coherently propagate east, with the centroid perhaps reaching the west central and northwest Pacific Ocean weeks 2-3. Last week I speculated a scenario suggestive of a slow evolution toward an equatorial Pacific Ocean warm event. While still in the cards, I am now less confident of that possibility. Again, monitoring within the WB (2007, 08) GWO dynamical weather-climate linkage framework is critical, and cook book techniques will not cut it! I am getting concerned that this latest MJO may be start of a process to rejuvenate a “weaker El-Viejo” which may persist into 2009.

Given the history of the last 5 MJOs, keeping in mind seasonal issues including the Indian/Asian monsoon systems, I think it is probable for a component of coupled tropical forcing to shift into the Western Hemisphere by weeks 3-4. The WB (2007, 08) GWO should circuit into phase 5, then collapse. Hence another strong event of meridional RWD amplification across the PNA sector typical of “WH (2004) MJO phase 8 plus La-Nina” is probable ~late week 2-week 3. The response regionally would be an anomalously deep north-south oriented trough across the western USA. Examples of the latter include ~1 December 2007 and recently ~22-23 May 2008. Both of these situations led to several periods of high impact weather across the Rockies and Plains, and were poorly predicted by the ensemble numerical models at least 11-14 days in advance.

While uncertainty is always there, I disagree with official forecasts stating there is currently not enough information to make probabilistic risk statements of temperature, precipitation, severe local storms, etc. beyond day 10. Relying on the models alone, not only for subseasonal predictions, but even much shorter time scales, is a cookbook and NOT meteorology (insert angry Rottweiler!). Once the work of the WB (2007, 08) GWO comes to maturity that will include tools such as overlapping statistical composites and an objective predictive scheme for the GWO (with hindcasts, etc.), a much more sophisticated evaluation of the numerical models will be possible.

Slowly shifting northwest with the seasonal cycle, ramifications of western USA troughs and a downstream eastern USA ridge are all too familiar. With variations in amplitude, this regional situation for the country appears likely to continue perhaps into early July. The “big event” discussed above may be the last week of this month or first week in July. Again, timing is a white noise deck of cards with the dealer being the Devil. Locations centered on Iowa may not have much relief from additional rounds of destructive severe local storms and flooding rainfall “until further notice”.

As discussed above, portions of the Arabian Sea into India/Indonesia and Southeast Asia/China are likely to be impacted by intense to severe thunderstorms during the next 1-2 weeks. During weeks 3-4 that area of enhanced rainfall may become focused from Southeast Asia into the Philippines and the west central Pacific Ocean. Enhanced rainfall may also appear across portions of Central and South America during weeks 3-4.

Please see the latest statements from the JTWC and TPC for tropical cyclone concerns. A late season tropical hazard may continue week-1 for the Arabian Sea and Bay of Bengal, shifting into the Northwest Pacific Ocean by week-3. The Western Hemisphere may have a less than climatological risk from tropical cyclones weeks 1-2. Other severe/high impact weather has been increasing internationally. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide.

Appendix

An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at

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

Links to CPC and PSD ENSO discussions: