“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.
The general thought is “ENSO neutral conditions with some lingering effects of La-Nina circulation” for at least the next few months. While in the views of many there is some truth to a statement such as the latter, care must be taken not to overlook the always important details of the subseasonal dynamics (which do impact seasonal outcomes). For instance, one response has been the warming of the equatorial east Pacific Ocean during the last several months, perhaps reflective of a “~year (-1) of a Rasmussen and Carpenter (1982) warm event scenario”. Please see links below, and stay tuned.
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
Three-day averaged OLRA have exceeded minus 90 W/m**2 with the Indian Ocean severe thunderstorm clusters. The area of enhanced tropical rainfall is oriented northeast-southwest, not only enhancing the monsoon systems, but also frontal bands even across southeast
During the last couple of weeks there has been some attempt to rejuvenate our low AAM base state. Leaving the westerly QBO phase in, global relative AAM dipped to roughly 1 AMU below the R1 data climatology earlier this month. With the classic transition of Eastern Hemisphere tropical upper tropospheric circulation anomalies to Indian Ocean (west
These are only a handful of many reasons why global relative AAM tendency spiked to ~plus 20 Hadleys forcing the WB (2008) GWO into approximately octant 4 of phase space on 20 July. Both AAM tendency and the GWO are headed back down (through 21 July), and whether the rejuvenation discussed above is a longer term signal remains unclear (not to contradict other weather-climate signals).
Broadly, there continues to be good tropical-extratropical coupling, including interhemispheric meridional symmetry of zonal mean zonal wind anomalies favoring anomalous midlatitude ridges. Comparing recent daily mean 150mb vector wind anomalies to the MJO composites, phase 3 of 250mb psi is loosely representative (“apples and oranges” issues understood). For instance, there is a well defined Rossby wave energy dispersion (RWD) signal from the west Pacific Ocean cyclones that links up the trough-ridge-trough pattern across
The careful reader will also see these signals in the GWO composites. Avoiding more length and confusion, there is ~50 day period between the recent minima in the time series of the global frictional torque. This leads to the point that decay time scale processes explained by the WB (2008) GWO are currently at least as equally important as any MJO contribution. Hence my feeling (one reason) why the notions suggested by the phase 3-4 composites of the GWO may be representative for roughly weeks 2-3. We need to remember these composites are still centered on 1 July (should be updated soon), and that using these must be defended on sound scientific reasoning, not “shoe horned”. In any case, this thought is consistent with my discussion posted on 12 July.
For the North American sector, perhaps ~days 10-20 (roughly 2-13 August) ridge amplification off the west coast into
Intense to severe tropical thunderstorm activity should shift east and north through portions of
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.
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 temperature, precipitation, geopotential height 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, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook!
Given shift work and travel, updates are extremely difficult. I hope to do another discussion around the weekend of 2-3 August.