Thursday, January 14, 2021

Models Indicating Chances For Precipitation Next Week

The lights of LA, above from Lick Observatory, this morning. At bottom, some sunrise color from Bondurant, Wyoming ( a bit southeast of Jackson).

Forecast models have changed quite a bit at longer time frames during past 36 hours or so. The GEFS plumes (above from 06 UTC last night) are now indicating chances for a rainfall event at the airport around next Tuesday and Wednesday. Yesterday morning the models were dry for the Southwest out through 15 days - so this is quite a change in the forecasts.

The 500 mb forecast (above from 06 UTC GFS) valid at 18 UTC on next Thursday indicates a sharp short-wave over western Arizona and northwestern Mexico. The blocking ridge has both shifted westward over Alaska, and also been undercut by a strong southern stream. These two streams merge  on the backside of the Arizona short wave.

This feature has gotten far enough south to bring a strong influx of subtropical moisture northward into Arizona (the first system forecast to do this in many months). 

The same GFS run forecasts a very substantial precipitation event for Arizona (below, showing precipitation forecast through 18 UTC on Friday the 22nd). If these forecasts actually verify, we would see the most significant rainfall event here in Tucson since late July. We now have something to keep an eye on - finally.

No comments:

Post a Comment