Wednesday, March 02, 2016

Atmospheric River Forecasts

Alex Tardy, SOO at NWS San Diego, posted some forecasts of atmospheric rivers (ARs) to the MAP weather chat-list maintained by SUNY, Albany. These are very interesting and I've explored a bit more. the graphics are from the Plymouth State Weather Center - see
These graphics illustrate yet again how far ahead of the NWS the universities and private sector are wrt providing interactive and diverse products derived from the NWS model forecasts.
 The forecast above is from the NWS GFS forecast and shows predicted Integrated Vapor Transport (IVT) over the eastern Pacific valid at 00 UTC next Tuesday, March 8th. The forecast below is derived from the GEFS ensembles and shows a Hovmoller diagram of the forecast probability of IVT > 150 kg/ms. The probabilities are derived along the inland string of dots shown in the right panel. (Note - to find these products at the Plymouth State url click on the "Research" tab at upper-right and then click on "Atmospheric River Portal".)

Above and below are zooms to our area of interest (from about 25 N to 35 N). These forecasts indicate that a weakening AR sneaks across northern Baja and brings moisture and precipitation to southeastern Arizona. 

Finally, graphic below shows the NWS plumes product for QPF at TUS. The ensemble members don't quite forecast a 100% chance of measurable precipitation at this time (i.e., from the 00 UTC forecasts last evening). Two members (of twenty-one) remain dry through the forecast period shown. However, prospects for some rain are certainly looking up, although amounts in the GEFS forecasts vary wildly at this time.

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