MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Lateral Rex Block In Northernmost Canada (Weak -AO Signal) Chills The Great Lakes, Northeast....
Plymouth State University Weather Server (3)
The presence of a durable, strong ridge over the western states (occasionally expanding into the Great Plains and Dixie states) implies persistent west/northwest flow across the Midwest and into the Eastern Seaboard. With some ridging taking shape in northern Canada (a lateral Rex signature), the suppression of shortwaves into the Ohio Valley and Mid-Atlantic region allows for a cold outlook in the Great Lakes and Northeast for the medium range. Moisture will not be easy to come by with this type of storm track, which I think ultimately will be close to, or above, 40 N Latitude. That means the best snow chances should be from MN and WI into New England, with rain and even some thunderstorm potential from the Corn Belt into the Virginias, Pennsylvania and New Jersey. Snow lovers should remember that March sun angle which helped to derail the Washington-Baltimore-Philadelphia "blizzard forecast debacle" that rivaled that of the March 2001 "Pamela Anderson Special".
....While Leaving The Intermountain Region, Great Plains And Old South Largely Mild And Dry
It may be true that the 12z operational European model features some strong cold expressions for the Midwest and parts of the Eastern Seaboard in the medium range. That said, the ECMWF ensemble package was milder overall, and the parent equation showed weaker displays of ridging over Nunavut AR than in previous runs. So on the idea that the Great Lakes and Northeast will stay cool, with the immediate West Coast neutral, the rest of the nation sees a mild-to-warm regime emerging in this time frame. Shortwave energy would largely miss a very dry stretch of the U.S., and chances for strong positive temperature anomalies seem likely in Texas, the Great Plains, and occasionally into the Ohio Valley and Deep South as well.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Why Are Europeans Better at Predicting Weather?
Return Of The Cold West, Warm/Mild Central, East Alignment; Severe Thunderstorms Threats Grow For Great Plains And Midwest
Allan Huffman (2)
Pennsylvania State University E-Wall
Before accepting any longer term forecasts, I always ask two pertinent questions: have the same weather scenarios panned out in earlier predictions, and do satellite images support the conclusions? Since we know that the computer models have had a miserable time this winter season with the predictions for high-latitude blocking (take a look at current maps to understand this notion, and notice the upward jog in the Arctic Oscillation signal...), I believe that outlooks for a cold March and Spring season are chancy at best. And the lack of a strong pulse from the Madden-Julian Oscillation into the polar westerlies would seem to suggest that calls for widespread, strong blocking signatures are unlikely to verify. Note that the ECMWF series has backed off from its vigorous Baffin Island block (now a much weaker 546dcm core at 500MB on March 19 before breaking down), and the other model suites embrace a largely mild alignment outside of the West Coast and New England.
There seems ample potential for a fairly intense storm to move from California into the "Four Corners" vicinity, then making a run east-northeast into the Mid-Atlantic or New England states in the 11 - 15 day period. This type of track in middle or late March normally brings abundant wet snows from the Front Range into the Upper Midwest and Great Lakes through parts of New England. Heavy, cold stratiform rains in the Corn Belt into the central Interstate 95 corridor, and intense thunderstorms from the lower/middle Great Plains and Old South are probable threats if such a disturbance develops and takes the track described by the GFS ensemble packages form 12z March 9.
So on the idea that a mild-to-warm configuration arises across the lower 48 states, what happens to the energy and moisture over the northern Pacific Ocean? In a neutral ENSO signal that lately has been bordering on "La Nina" territory (-0.6 ONI measure for DJF), we must pay close attention to the strength of the snowpack (near normal placement and depth) and the soil moisture array (very dry outside of the Mid-Atlantic region and Mississippi Valley). Since extension of the snowfields is highly unlikely (this is March, remember?), a negative-neutral SST anomaly signal over the equatorial waters between the Galapagos Islands and the Philippines leads me to favor dominance of ridges east of the Continental Divide. Accounting for the area of wet soils in parts of Dixie and the East Coast as a likely weakness zone (keeping in mind the intense drought over Florida and Georgia), I can see some opportunities for strong convection from the lower Great Plains and the Old South and parts of the East Coast. The jet stream configuration will allow of expansion of the heat ridge from the Greater Antilles, so the outlook for a warm MAMJ period seems to be a sound one.
If we follow an "almost weak La Nina" base through the upcoming summer against the still-widespread dry soil moisture levels, then three topics will surely arise. One is widespread heat outside of the Pacific Northwest and New England. Another is an early, and active tropical cyclone season. Plug in the neutral ENSO ONI years as analogs (there are plenty), and add on a similar drought year that is somewhat of a step down from last year's horrific scorch in the central and southern reaches of the nation (1937). We may catch some temperature breaks later in the summer, but a searing display of ridging should be apparent by May and reaching a peak in July. And yes, the comparison group of summers I am using has high emphasis on Florida and Gulf Coast hurricane threats.
It may have been a dull winter for some, but the next two seasons look to be interesting, to say the least....
Prepared by Meteorologist LARRY COSGROVE on
Saturday, March 9, 2013at 7:45 P.M. CT (Part 2)
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Copyright 2012 by Larry Cosgrove
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