Arctic Front With Possible Gulf low Feb 10th-11th

jmundie wrote:12z unmet didn't cut off the high in Alaska. Kept the full latitude ridge.

ONE THING INTERESTING TO NOTE HOWEVER. THE ONE THING THE MODELS DO
SEEM IN AGREEMENT ON...IS THE DEVELOPMENT OF A PERSISTENT NEGATIVE
ARCTIC OSCILLATION. IF THIS FEATURE DEVELOPS AS THE MODELS CURRENTLY
SAY IT WILL...MORE COLD AIR INTRUSIONS INTO THE MID LATITUDES CAN BE
EXPECTED IN THE COMING WEEKS. IN FACT...IT LOOKS LIKE THIS WILL THE
CASE BY NEXT WEEKEND INTO THE FOLLOWING WEEK...WITH A MORE AMPLIFIED
PATTERN DEVELOPING IN THE MAJORITY OF THE MODELS. THE 12Z ECMWF AND
GFS BOTH SUPPORT THIS IDEA OF A DEEPER EASTERN TROUGH...WHICH WOULD
ALLOW FOR MUCH COLDER WEATHER LATE IN THE WEEK AND INTO THE
FOLLOWING WEEKEND. THERE IS ALSO SOME SUPPORT FOR THIS SCENARIO IN
THE DGEX AND CANADIAN MODELS. THIS WOULD ALSO SET THE STAGE FOR
SUBSEQUENT SURGES OF COLD AIR SOUTH INTO THE OHIO VALLEY INTO MID
FEBRUARY. THUS...AFTER A PROLONGED PERIOD OF WARMTH...IT LOOKS LIKE
THE PATTERN COULD BE SHIFTING TO A COLDER ONE...AND PERHAPS MORE
CHANCES FOR SNOWFALL.

No, your eyes have not been deceiving you. All of the numerical models have flipped and flopped wildly over the past week or so. The usually consistent ECMWF version has been notably horrid, having issues with both the subtropical jet stream and the sequence of storms digging southeastward from the Pacific Ocean. You kind of expect the GFS model suite to have issues with many conflicting systems (split flow in a La Nina episode....), but the European panels are very much out to lunch of late and should NOT be trusted to present an accurate picture of weather past Day 5. One feature that we can gather will be a player in the medium range is the Hudson Bay vortex. IF the cAk gyre acts in concert with the disturbance drifting into Baja California (which I think is likely), then we cannot rule out a potentially impressive winter storm across the Deep South, Appalachia, and the Eastern Seaboard (see more below).

The 18z GFS model suite confirmed what many were thinking about the threat for a Gulf Coaster + Nor'easter storm event in the February 11 - 14 time frame. The operational American model has been touching on this idea for some time now, and I suspect that the actual case of cyclogenesis will be stronger than what has been depicted, perhaps greatly so. The ensemble series at both 12z and 18z on Saturday maintain some sort of ridging along the West Coast while hinting at some expression of -AO and -NAO styled ridge placement. The clincher in this is that the standard European version shows a sharply-defined positive height anomaly into Greenland in the 6 - 10 day range. While such a signal does not make a East Coast winter storm threat a certainty, the model may be trying to express the danger of 500MB height falls directly beneath the ridge complex. If so, the potential for pressure falls and heavy precipitation would increase.

snow for the higher elevations of the southern Apps Monday night. Not much, but a synoptic system and just cold enough, so for this season thats' worth a mention.
the other system to watch is the strong s/w or closed low dropping south from Canada at 120 hours. The European a few days ago had this crossing the Tnn. Valley and Carolinas . Its very powerful to start but the GFS loses it instantly at 120. Meanwhile the flow from Canada is diving south, southwest, as the ridge tips in northwest Canada. So cold is lurking from around I-40 from Ok. to NC....the Gulf could open and back with a system to watch.

GFS almost totally absorbs the southern stream, and has been inching toward that for awhile now. Only time and a couple more runs will tell though, but if it does, then a major East Coast storm will run up the coast, as a snowmaker in the Deep South/Tn Valley to Apps and eventually East Coast. You can't rule it out until we know that the Baja system hangs well back and detached from the flow. GFS is extremely close.

Atleast a storm, probably the first east coast snow storm this season, but I distrust the GFS on which wave does the trick. There are going to be changes with this, similar to what just happened (and will happen Monday) with the energy hanging back. If the model focuses on the wrong s/w to develop the storm then more areas will experience a big event with the second s/w coming in from Mexico. One of the closest calls to fully phased I've seen since Christmas storm 2 years ago. Definitely a possibilty since its that close, but keep your expectations low in phased events south of DC.

The GFS has been on this for a while showing a possibility. Its actually not nearly as warm to start as it was looking earlier (thank you height falls and Monday's wave). But to get the 2 streams to merge will be a feat. However this has been shown to be one extremely tall PNA ridge by both models for atime now, so we'll see. Can't rule out a major event but odds are always against a phased event this far south, but it does happen time to time (Jan 87). If the models hold on to that extremely strong s/w topping the ridge (remember ecmwf had it several runs as well--just different track), and the closed off low in the Baja or Mexico is withing grabbing distance, then there would be a phase and a huge event developing on the East coast. However, what could go wrong is just as big. If the Baja system is too far removed, which is very possible, then we're looking at a dry cold frontal passage. Also, for areas east of the Apps to get snow in this setup is a long shot since the cold has to cross the Apps. Its' much more likely west of the Apps and right to the mtns. However, one good thing this particular time is so far its not that warm aloft since the Baja system is extremely far south to begin with. An ideal situation would be the Baja low develops a nice surface low and backing winds once it reaches the central gulf and forms a wave that travels offshore Savannah up the coast. Odds are against it exactly but its close.

snowdog wrote:Euro out to 120 on instant maps...nothing all that exciting. Really deep vortex up in northeast Canada but we don't get to taste it. Cutoff in the SW is touring Mexico. Crap so far.

REGARDING SPECIFIC MODEL PREFERENCES...THE 00Z GFS LIES FURTHEST
FROM THE MODEL CONSENSUS WITH THE LOW CROSSING BAJA CALIFORNIA AND
WITH THE SHORTWAVE TROUGH CROSSING THE MIDWEST ON DAY 3/WED.
THUS...HAVE NOT USED THE GFS IN THE PRELIMINARY PRESSURES/FRONTS
DESPITE BECOMING MORE PREFERRED IN THE WEST BY DAY 6/SAT...AS IT
MAINTAINS THE RIDGE IN A MORE PREFERRED ORIENTATION. OTHERWISE...A
BLEND OF THE 00Z ECMWF AND ITS OWN ENSEMBLE MEAN IS THE PREFERRED
CHOICE FOR DAY 3-5 BEFORE ABANDONING THE OPERATIONAL ECMWF
ALTOGETHER BY DAY 6...AS IT APPEARS TO ERODE THE RIDGE OVER THE
WEST TOO QUICKLY.INSTEAD...RECOMMEND THE ECMWF ENSEMBLE MEAN
WHICH IS SUPPORTED WELL BY THE 00Z GFS...ESPECIALLY IN THE WEST.

JAMES

jmundie wrote: dgex brings -20 850s to kentucky, and a light snow event for tennessee as well.

snowdog wrote:Looks like a clipperish type system for Middle-TN, maybe an inch or two if ground temps cooperate.

jmundie wrote:There is now a tropical disturbance in the gulf.

This just got interesting.....