“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 91-day signal to noise ratio anomaly composites are now updated daily, centered on the date shown (see product descriptions). There have been on-going map room issues causing missing data and unrepresentative plots.
The warmest SSTs globally persist across the Tropical Northwest Pacific Ocean (TNWP) with totals exceeding 30C east of the
Subsurface negative anomalies continue to shift east along the equatorial
Finally, it is my feeling that the JJA ONI of -0.1C based on Nino 3.4 does not scientifically completely represent the interannual component of the global weather-climate situation. The roles of other tropical ocean basins and their impacts on global circulation dynamics must be considered.
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
Full disk satellite imagery and other tools indicate there has been a slow coherent eastward shift of
The WH (2004) methodology gives roughly a 1 sigma projection in octant 4 of phase space, and nearly a 1.5 standard deviation shift in octant 3 leaving the base state in. Phase 4 of the composite streamfunction (psi) anomaly plots centered on 3 September nicely represent current tropical and even PNA circulation anomalies. I think the latter is true given a growing MJO signal. However, I also think the interannual component will remain significant.
Global relative AAM is still well below the R1 data climatology, more than 1 sigma (~1 Atmospheric Momentum Unit (AMU)), removing the stratospheric westerly phase of the QBO, through 3 September. Using this same measure (no QBO signal), relative AAM is still up about 2 AMUs compared to a year ago, meaning more subtropical westerly wind flow. However, Rossby wave trains interacting with the tropical convective forcing and midlatitude mountains (explained by the WB (2008) GWO) have led to a strong negative AAM tendency of roughly 15 Hadleys. Much of this negative AAM tendency is coming from the Southern Hemisphere. Hence the WB (2008) GWO continues to “hover” around octants 1-3 of phase space.
Constructively interfering with the MJO signal, phase 3 of the GWO composite psi anomaly plot is representative of the on-going “Branstator (2002)-like” positive phase of a circumglobal teleconnection. The subtropical sink-midlatitude source AAM transport signal, strong in the Southern Hemisphere and weak for the Northern Hemisphere, support this notion. Synoptically this means our global circulation base state favors stronger than normal subtropical and midlatitude ridges.
So, where does the global circulation go from here? First, I think there is some coupling between the GWO and the MJO. Secondly, and arguably not emphasized enough and stating redundantly, I think there is an eastward propagating Eastern Hemisphere MJO signal.
Most models suggest propagation into roughly octants 5-6 of WH (2004) phase space by late week 2 or 3. Given the cold Dateline SSTs and other reasons I have, I agree with the eastward shift, but possibly truncated. The enhanced tropical forcing is probable to propagate east-northeast, focusing on the warm TNWP by ~week 3. A weaker MJO signal should then continue into the
The WB (2008) GWO is likely to continue its 10-20 day periodicity orbiting from octants 8-1 to 4-5 in phase space, leaning toward low AAM, while “riding along” with the MJO signal. Phases 4-5 of the MJO psi (and temperature) composite anomaly plots appear reasonable for weeks 1-2. Phases 6-8 may be representative for ~weeks 3-4. Regardless of the white noise details and timing, 1) I am concerned another prolonged period of Western Hemisphere-Indian Ocean active convection is possible after week-two (MJO phases 8-1-2), and 2) at some point there is likely to be an anomalous extended North Pacific Ocean jet collapsing into a western USA trough, like that shown by phases 8-1 of the WB (2008) GWO. Keeping in mind issues of boreal autumn, the latter may be most probable the last 10 days of this month into early October. My confidence is still low in the outlooks that follow.
Per above, currently much of the
Again, possible impacts onto the
In general, heavy precipitation is likely for much of the country east of the
As already discussed, intense to severe tropical thunderstorm activity is likely to propagate east and northeast initially impacting Southeast Asia and Indonesia, then focusing on the Philippines by week-3. Portions of the equatorial
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 (high impact weather events are continuing).
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 introduce the GWO (WB (2008)). 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! I hope to do another discussion next weekend, ~13-14 September.