MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Moisture-Laden, Cold-Driven Storm Hits West Coast, Intermountain Region February 7 - 9....
ECMWF (2)
The process may be very slow, but the interaction between the equatorial moisture axis west of Baja California and the storm complex below the Aleutian Islands will be in full swing starting February 7. The two features will effectively combine into one strong disturbance over Oregon and California, with a sharp drop in temperature moving from the West Coast into the Salt Lake Valley and Desert Regions. As was the case in previous storms this winter season, lower elevation rain and thunderstorm activity will be accompanied by mountain snowfall and a bout three days worth of below normal temperatures.
....That Presents Extensive Severe Weather, Heavy Rainfall Threat Across Eastern Two-Thirds Of U.S. (With Cold Air Returning To The Great Plains)
WEATHERAmerica
NOAA/NCEP
Plymouth State University Weather Server (3)
After reviewing the numerical models, it has become apparent that a major storm will organize over the southern/central Rocky Mountains on February 9. The computer outlooks suggest an outcome along the lines of the system that targeted the Old South and Eastern Seaboard with severe weather, heavy rainfall and strong winds on Tuesday and Wednesday of this past week. The track scenario may unfold somewhat more to the south than what is shown by the operational GFS series, but I think that particular scheme has a better handle on the evolution and character of the disturbance.
Because there should be a prominent tropical moisture fetch (with mesoscale disturbances involved) becoming involved with the storm, rainfall potential and severe thunderstorm development may be a bit longer-lived from portions of Texas into the Deep South. Enough cold air should be present to allow for a significant snow event across parts of the Intermountain Region, Great Plains, and Upper Midwest, with some manner of changeover from rain to snow to the north and west of the trajectory of the surface pressure falls. Gusty north winds may kick up the snow cover in the north central states, while blowing dust may be a problem in parts of West Texas.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
IRI Summary of ENSO Model Forecasts
Huge Circumpolar Vortex Over Hudson Bay Boxed In By Warm 500MB Ridging In Gulf Of Alaska And Northwestern Atlantic Ocean; Cold Air Stays Lodged Between Rocky Mountains And Appalachia With Strong Storm Threat Across Southern, Eastern Tiers Of U.S.
USAF (2)
NOAA/IMS
University Of Nebraska HPRCC
IRI/Columbia University
Environment Canada
NOAA/CPC
Pennsylvania State University E-Wall
Winter is not dead yet. But (groundhog opinions excluded), for many in the U.S. outside of the heartland the season will be on life support.
Despite numerous ensemble package forecasts for blocking scenarios in January, the 500MB longwave pattern has remained fully progressive though the lower 48 states. Analog predictions were almost 180 degrees from the reality that the coldest values occurred over the West and strong warm-ups demolished periods of cold across the eastern two-thirds of the nation (present temperature pattern excluded, of course). Yes, this winter IS colder AND snowier than last year by about 15 percent. But aside from volatility issues, I am confident that the DJFM time frame will have largely warm averages in the highest population centers.
The neutral character of the ENSO episode is likely to continue through the coming autumn season. For the summer and fall, that should mean a fairly hot (and front loaded) temperature display with (possibly) an early and active tropical cyclone season. Going from mid-February into March, I like the idea of cold dominating the center of the continent with warmth (mostly) holding on across the Gulf Coast and Eastern Seaboard. The Hudson bay vortex should be quite strong in the 11 - 15 day period, so I would not rule out a transient shot of bitter cold into the Mid-South and Eastern Seaboard. But the averages of thermal anomalies should play close to what is shown on the NAEFS depiction.
Another storm should organize over Texas and the western Gulf Coast around February 12. This feature will form as a result of a "left behind" cold pool and energy which separates from the major disturbance predicted to occur in the medium range. The trajectory of the extended period low pressure system looks to be along the spine of the Appalachian Mountains or through the Piedmont and Atlantic Coastal Plain. This type of path would allow for significant snowfall from the Ozark Plateau through much of the Midwest and Great Lakes, before the low moves into Quebec by February 15. I would not rule out a third, weaker impulse along the trailing frontal structure in Dixie and the East Coast around February 17 - 19.
Without blocking signatures at high latitudes, it is unlikely if meaningful snow and ice accumulations, along with entrenched cold, will occur in the lower 48 states east of the Continental Divide. Spring is really not that far away for many of us.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, February 2, 2013 at 8:00 P.M. CT
Disclaimer:
The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.
Copyright 2012 by Larry Cosgrove
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