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. (note the initial projection) (link 18).


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

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. 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:

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). .

The following is a link discussing recent global weather and related events.

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.

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

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