Friday, December 24, 2010

A Look Ahead To The End Of 2010

The area around Hawaii, and off to its west and southwest, continues to be very moist and acting as a nearly stationary source region for extensive moisture plumes. The top image shows the east Pacific PW product from CIMSS (at Univ. of Wisc. in Madison). Two intense systems that are strongly blocked in the western Pacific and east Asia are pulling a large stream of moisture back to the northwest toward Asia. The deep 500 mb trough south of Alaska has pulled a separate moisture stream north-northeastward to British Columbia. A very very interesting situation across all of the Pacific, and I don't have any real feel for how unusual all of this might be.
The bottom two panels show operational versions of the 500 mb forecasts valid at 168 hours (0000 UTC Friday December 31st) from the 0000 UTC model runs last evening. In an interesting reversal of the usual situation, the NWS GFS has a stronger system over the West and one that is centered further west than the similar trough forecast by the ECMWF. The GFS seems to have forecast stronger blocking west of, and over, Greenland, which is keeping the upstream features further west. This is a bit of a dilemma, since the ECMWF has usually been superior to the GFS at longer ranges. The GFS forecasts a fairly significant and widespread precipitaion event across much of the Southwest US centered out around 156 hours (all 12 of the GFS ensemble members have preciptation in the Southwest and southeastern Arizona for several periods, which is quite impressive for the GFS). Thus, the GFS forecasts a wet ending for 2010, while the ECMWF is more ambiguous. Guess I'll have to root for the GFS!
Hope that everyone who visits here has great Holiday weekend!

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