This will be a shorter discussion. There have been no significant changes to the global tropical and extratropical SSTs during the past week. Some warming to near climatology has occurred across the equatorial
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
While I am not by any means surprised, the Eastern Hemisphere moist tropical convective forcing discussed a week ago did “unexpectedly” propagate eastward into the very warm southwest
While some may suggest that this
I am thinking that the Western Hemisphere tropical forcing is “taking over”, and will lead to a rapid intensification of deep moist convection across the currently suppressed
There is a zonal wave number 2 baroclinic circulation response across the tropics, including anomalous twin upper tropospheric anticyclones at ~140E. RWDs from the latter arc nicely to the developing western
Summarizing the above, the WB (2007, 2008) Global Wind Oscillation (GWO) has orbited to phase 2 having a greater than 1 sigma projection. The MJO component has been “in step” with the GWO recently; however, whether or not that continues is unclear. I do think that more circuits around GWO phase 3 are probable for at least the next few weeks, particularly if our La-Nina base state becomes enhanced.
There are no major changes to my
As shown by the models for week-1, several synoptic events leading to potentially widespread and destructive high-impact weather are likely for the CONUS. Locations already hit hard by flooding and severe local storms may experience numerous rounds focusing on locations from Southern Plains to
However, after week-1, status quo appears probable to return for the lower 48 states meaning a northward shifted storm track. As tropical forcing increases across the Indian Ocean, retrogression of existing circulation anomalies is probable week-2 suggestive of troughs just off the
Severe weather internationally has remained relatively tame during the last week. I continue to leave it to the expertise of the appropriate weather centers internationally to alert the public of these risks.
Intense to severe thunderstorm activity should decrease week-1 across tropical South America while spreading into central Africa and the equatorial
The west central into the southwest
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
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:
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 preparation by WB that will formally introduce the GWO along with subseasonal composites. Given shift work and upcoming travel, updates remain extremely difficult. I am planning on posting another discussion next weekend, 12-13 April.