Weak System Currently progressing through the West Coast Upper Ridge….Some light rainfall occuring this morning in the Town of Mammoth with about an inch of Snow over the upper elevations as expected…….A fair but Partly Cloudy Weekend is expected…..
Thursday November 13, 2014
Posted at 6:36 am by Howard
Will update late this afternoon…..Time permitting..
Thursday Am Update:
New 12Z GFS has just finished running. The west coast ridge is a bit weaker on this mornings run. The Short Waves (Storms) for Tuesday/Wednesday and again early the following weekend are more progressive. This once again enhances the odds for snowfall in the high country next week. Will have a look at the 12Z ECMWF as soon as it finishes about 12:00 PM today. The 12z GEM as well.
This Mornings extended guidance continued the trend showing an amplified upper flow pattern at 18000ft from the central pacific to the east coast of the CONUS. The models are predicting trofs to remain over the Bering Sea/Aleutians and East/Central North America.
The pattern continues to be very amplified including the more dominant west coast ridge in between. This morning Global Forecast Model’s (GFS) deterministic run continued the trend of “Some” short wave energy undercutting the west coast upper ridge next week. However, the trend is certainly weaker with the mid week short wave. IE the Tuesday/Wednesday storm)
Looking at the 2 week ECMWF 5 day means hemispheric guidance, the planetary wave pattern transits to a three wave from the current four wave pattern. The Blocking high over NWT/AK is expected to retrograde to Siberia, while the trof over the Bering Sea is expected to progress eastward into the Eastern Central Pacific. The upper flow pattern over the eastern pacific should become more active during week 2 with the upper jet aimed more toward Northern CA and Oregon. The Pacific NW is thus likely to get another bout of heavy precipitation week 2. At the moment, 500MB 5 day means between the 22nd and the 27th of NOV for heights on the ECMWF 500mb Ensemble control are still about 570DM over Mammoth, which is border line for precipitation here in the central sierra, unless it taps a lot of subtropical moistures along the way. The Dweebs will follow the trend to see what changes there may be in the location of the upper jet the next couple of weeks.
In conclusion, fighting the west coast upper ridge….The models have been back peddling on the Tuesday/Wednesday system the past 2 days…. As it is not clear at this time on how it will hold together as it comes through the west coast ridge Tuesday night and Wednesday. If I had to take a wild guess at this point I would say any ware from a couple of inches to as much as 8 inches depending on again….how it holds together, or if it splits and goes south into Southern CA. With that said, the upper ridge will begin to weaken next week as the upper pattern goes into transition later in the week. If by chance the upper trof over the Bering sea decides to progress further east to say 130W to 140 west…..that would make a big difference in heights over the central west coast.
As a side note; even though a lot of the teleconnection’s and indices effecting what we might expect weather-wise across the US are different this year, the eastern pacific ridge is still the dominant feature effecting California’s weather and for that matter its ongoing drought. So far, the expected enhanced upper jet has yet to show up related to the developing El Nino. However, that is not unexpected, as it is still only mid November as the East Asian Upper Jet out over the Pacific is still quite incipient.
Dr Howard and the Dweebs……………………:-)