Friday, July 04, 2008

Reprisal -- Is the Witch Dead???

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

I am going to work to make these postings shorter and focus more on the products contained in the experimental dedicated web page that is only in the infancy of development, per Appendix in previous discussions. One important purpose of these discussions is to provide a much needed climate service for all users. The web link is

To keep us “vigilant” about the interannual variability component, I will leave the following links in. While there has been a bit more respectable warming of equatorial eastern Pacific Ocean SSTs (~ plus 3-4C anomalies at 50m depth) along with other measures suggestive of a possible eventual evolution toward an El-Nino, I think the interannual signal remains unclear. I will give attention in these postings should that change. Please remember that “ENSO neutral” does not at all imply there will be a lack of robust subseasonal events leading to global high impact weather situations. (note the initial projection) (link 18)

Full disk satellite imagery etc. indicates multiple regions of enhanced tropical convective forcing. These include the Eastern Hemisphere monsoon systems into the northwest Pacific Ocean, the Eastern Pacific Ocean ITCZ through the Americas and the western Indian Ocean. Complicated interactions with the extratropics have resulted in this pattern, and can only be understood with rigorous daily monitoring utilizing the WB (2007) GSDM. In any case, a strong MJO projection in octant 1 of ~2 standard deviations in WH (2004) phase space, with the very important interannual base state left in, has resulted. To me, this is still MJO #6 since boreal fall 2007.

Updated through 2 July, there is little circulation projection in the WB (2008) GWO phase space. However, this phase space depicts a dynamical evolution of the global atmosphere (not static!!! --- insert angry Rottweiler). For instance, as part of several attempts to increase westerly wind flow globally since late 2007, such has been the case since roughly mid May. Bands of zonal mean westerly wind flow anomalies have been propagating poleward off the equator with downward transport (by the baroclinic eddies), only to undergo frictional dissipation in the midlatitude storm tracks. Even though the latter has recently been most robust in the Southern Hemisphere given austral winter, for the Northern Hemisphere there has been zonal mean dissipation ~20 and 50N. Hence the global friction torque is ~minus 20 Hadleys, one of the lowest values since late 2007.

The point is that I expect to see global relative AAM decrease very soon (restatement from my last posting). Relative AAM tendency is probable to become strongly negative as the global mountain torque becomes negative and a poleward transport signal develops in both hemispheres (please see description and schematic on the web page). Hence the WB (2008) GWO is likely to orbit into octants 2-3 during the next 1-3 weeks. This will again be a situation where both the WH (2004) and WB (2008) phase spaces are similar, ~2-3. Evolutions such as this may rejuvenate our low AAM base state.

Referring to the MJO composites for ~250mb streamfunction (psi) and 2m air temperature, octants 2-3 suggest an increased probability of a northwestern USA trough with a ridge across the eastern states. The 2m air temperature patterns are the expected “cool west-warm east”. Keep in mind these are composite signals, hence relatively weak. The GWO composites are similar, but show a nice progression of coolness shifting into the central part of the country and heat returning to portions of the west (still warm for much of the east). I prefer the latter and suspect phases 3-4 of the GWO will be most probable by ~week 3 based on results discussed in our submitted paper to MWR. Most models are catching on to this notion for weeks 1-2.

The precipitation patterns should be well understood. After a fairly quiet few weeks (relatively speaking), intense to severe MCS activity for much of the Northern Plains into the Ohio Valley is a concern starting next week. This activity may become particularly intense in terms of flooding rainfall weeks 2-3 while drifting slowly southward (focus on Iowa and Missouri?).

Intense to severe tropical thunderstorm activity is probable to increase from the Indian Ocean into the monsoon systems and frontal bands of India and Asia during the next couple weeks while the west and northwest Pacific Ocean stays sporadic. In fact, tropical cyclone spin-ups for the latter threatening the Philippines and Southeast Asia cannot be ruled out. The East Pacific Ocean tropical cyclone hazard should wane during week-2.

The warm north tropical Atlantic Ocean basin defied my concerns related to tropical cyclone climatology expressed a week ago with the development of Tropical Storm Bertha (was not surprised). With upper tropospheric anomalous twin tropical anticyclones returning to Africa and the Indian Ocean from the Western Hemisphere during the next 1-2 weeks, additional strong African easterly waves are probable. 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.


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. 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. 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

Overlapping seasonally varying subseasonal composites for variables such as surface temperatures, precipitation 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 12-13 July.

Ed Berry

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