Tuesday, January 12, 2016

Weather Systems For Western US Shift Northward

After a wet start to January, the primary storm track across the north Pacific has been shifting northward, leaving much of the Southwest looking ahead to a dry week or so. Above is this morning's GFS analysis of the 300 mb level. The strong split in the flow, that typifies El Nino winters, remains distinct off the West coast, but the southern branch of the flow has weakened and shifted southward. The main storm track for next week or so will continue within the northern branch of the flow. The 168-hour forecast of total precipitation for the next week (from the GFS operational member run at 00 UTC last evening) is shown below and forecasts a very wet week from northern California northward and northeastward, with mostly mountain precipitation for parts of the Southwest.

The forecasts from CPC illustrate how fickle the monthly outlooks can be. The outlook above is for January 2016 - the northward shift of the storm track means that much of their outlook for the West is not going to verify well. The outlook below, also from CPC but from yesterday - January 11th, is for the period from January 19 through 25. This outlook is more in sync with the current pattern and essentially reflects persistence for the next two weeks - however the pattern remains volatile over the Pacific, and CPC may end up chasing after the evolving synoptic patterns for the rest of the month.

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