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Nov. 27th - Nov. 29th Upper Level Low

LithiaWx

By LithiaWx,
in Southeastern States

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LithiaWx

LithiaWx

Posted
Posted

some of the Globlal models have shown an ULL/cut-off closing off somewhere around the Mississippi River. This could mean a pocket of cold enough air aloft to support some light frozen precip, somewhere.... First winter storm thread of the young season, hopefully one of many!

I'll leave the technical stuff to the mets... Who knows how this pans out, hopefully this is a warm up to future bigger and badder storms this season. Consider it preseason! :popcorn:

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Southern Track

Southern Track

Posted
Posted

I haven't posted too much, but just wanted to say it's good to see potential with an ULL this early in the year. Hopefully it will pan out and someone will see some wintry precip flying. Just hope the patten long-term changes for sustained cold and not just transient.

some of the Globlal models have shown an ULL/cut-off closing off somewhere east of the Mississippi River. This could mean a pocket of cold enough air aloft to support some light frozen precip, somewhere.... First winter storm thread of the young season, hopefully one of many!

I'll leave the technical stuff to the mets... Who knows how this pans out, this is a warm up to future bigger and badder storms hopefully this season.

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WeatherNC

WeatherNC

Posted
Posted

Was going to post this in the Nov thread, but I guess the mojo verified... :thumbsup:

Aren't closed lows also very tough to predict as far as the path they will take?

Ensembles have been an absolute train-wreck over the past 48hrs, often times the operationals would be considered an outlier within there own suite. I have much love for the pros trying to forecast this one as the implications are BIG, and bust potential highly above avg...

If I had to make a forecast, I would blend 60/40 op ECMWF/GFS over the past two cycles, maybe flavor in a little UKMET to work out timing. Why? The operational models are preferred in this scenario due to better resolution which should handle several vorticity parcels that come into question, especially since there is a general agreement amongst them, even when factoring in some of the lesser knowns NOGAPS/JMA, and despite what the coarser grid ens members show. The parcel in question arrives in SoCal in about 48-60hrs, slips east through the 4-corners, and begins to interact with the dominant northern stream energy. The 12z Euro H5 maps are an absolute cluster over the intermountain west going into the central plains between 81-96hrs, no way imo a lower res ensemble would be able to handle that better when compared to the operational. After that, boosters are lit through the central plains, big time northern vorts coming down!

12z ECMWF @ 105hrs ( http://www.wunderground.com/wundermap/ ) ---> yeah, it's free

post-382-0-40079900-1321999274.jpg

12z ECMWF @ 162hrs ( http://www.wunderground.com/wundermap/ ) ---> yeah, it's still free

post-382-0-63089800-1321999286.jpg

This is going to be very tough to predict where it will close off, orientation thereafter looks pretty safe at SE-NW, best guess is over the middle MS river valley, maybe ozarks, who knows. With so much energy coming into the base of the trough, still a great deal of question on how it will interact, and when exactly it closes, but I think it will. After that, everything looks primed for a hard neg tilt, with a parent surface reflection somewhere in the OH Valley/GL region, and a possible second surface low getting cranked over N GA tracking NNE? as the trough tilts hard to the right. More energy coming down will likely alter the track, maybe swing it a little east, unsure what the met term is but I would think the physics principles of angular torque and momentum would apply here.

Despite what some on here see, myself included, the Euro is hands down the best model on the planet in terms of NH H5 verification scores less than day 7, UKMET 2nd, and global 3rd. For this reason, it would be almost foolish for someone to not give some/sig weight to its solution when considering run-to-run continuity, and other general agreement.

Granted things can and will change, they always do. I have been one who for along time never likes these extreme solutions in the extended, and while I think it is about time for this to have its own thread, going to go another 24-48hrs before I bite, but anyone with SE mojo feel free to make it.

This is not a run-of-the-mill upper level low, very different from the 536dm bowling ball we saw a couple years back, aka Foothill Mauler. Based on what I am seeing, and I am sure others, this is a almost textbook full-latitude upper air trough going closed low, possibly into the sub 200mb layer, over the TN Valley. Any secondary low that forms will have to be watched closely through the SE, as any clearing would likely result in one of the more active late season svr wx outbreaks we have seen in recent memory. Met fall going out with a bang, 2011, go figure, not surprised... :popcorn:

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NavarreDon

NavarreDon

Posted
Posted

Finally a winter weather thread!(Pressure is on Marietta :P ) Couple things real quick. Year before last didn't the GFS start pushing winter systems way way south only to bring them north in later runs? Maybe that bias has been corrected but maybe not. Here is the long term from this afternoons GSP afd. Pretty much a rehash from things that have been said in the main Nov. thread but thought I would post.

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...

AS OF 225 PM TUESDAY...LOW CONFIDENCE IN THE MEDIUM RANGE FCST.

GUIDANCE IN GENERAL AGREEMENT THAT A WX SYSTEM WILL AFFECT THE AREA

LATE SUNDAY INTO EARLY NEXT WEEK. HOWEVER...THE GUIDANCE CONTINUES

TO VARY WITH EACH OTHER AND FROM RUN TO RUN WITH THE DETAILS. THE

12Z CANADIAN IS THE MOST PROGRESSIVE WITH AN UPPER TROF MOVING INTO

THE AREA SUNDAY THEN AN UPPER OW CLOSES OFF OVER THE OH VALLEY BUT

THE BULK OF SYSTEM STILL MOVES WELL EAST OF THE AREA BY MONDAY. THE

12Z GFS NOW FAVORS A MUCH SLOWER UPPER LOW THAT CLOSES OFF FROM SRN

STREAM ENERGY IN THE UPPER TROF. THE LOW CLOSES OFF OVER THE SRN MS

VALLEY SUNDAY THEN ONLY SLOWLY MOVES REACHING THE OH VALLEY BY TUE

MORNING. THIS LOW MOVES NORTH INTO THE GREAT LAKES TUE AS ANOTHER

WAVE DROPS INTO THE TROF BEHIND IT AND FORMS A SECOND CLOSED LOW

OVER THE LOWER OH VALLEY. THIS RESULTS IN A MUCH SLOWER SFC FRONT

THAT MOVES INTO THE AREA SUNDAY AND SLOWLY MOVES EASTWARD ACROSS THE

AREA MONDAY AS A SFC LOW OCCLUDES OVER THE OH VALLEY. THIS WOULD

KEEP PRECIP CHANCES OVER THE AREA LONGER SUN NITE AND MONDAY AS THE

FRONT MOVES THRU. THEN PRECIP ASSOCIATED WITH THE UPPER LOW WOULD

MOVE ACROSS THE AREA MON NITE AND TUE. THE 12Z ECMWF HAS COME IN

TRENDING AWAY FROM A MORE PROGRESSIVE SYSTEM TO MORE LIKE THE GFS.

THIS WOULD HAVE THE HIGHEST POP MON AND MON NITE WITH RAPIDLY

DIMINISHING POP TUE WITH ONLY MTN PRECIP WITH THE UPPER LOW. THE GFS

ENSEMBLE MEAN IS LITTLE HELP WITH ONLY VERY LOW POP EACH PERIOD.

GIVEN THE MDL INCONSISTENCIES AND THE USUAL PROBLEMS THE MDLS HAVE

WITH UPPER LOWS...WILL START WITH THE NATIONAL GUIDANCE BUT TREND

TOWARD THE OPERATIONAL GFS/ECMWF SINCE THEY SHOW SIMILAR TRENDS.

THIS MEANS POP INCREASING TO CHC FROM WEST TO EAST BY SUNDAY...THEN

GOOD CHC POP SUN NITE AND MONDAY. WILL NOT FCST LIKELY POP ATTM

SINCE BEST PERIOD FOR PRECIP WILL LIKELY CHANGE SEVERAL TIMES

BETWEEN NOW AND THEN. HAVE CHC POP RETREATING TO THE NC MTNS BY TUE

AFTERNOON. AS WITH ALL UPPER LOWS...COLD TEMPS WILL MOVE INTO THE

AREA...WITH THE COLDEST VALUES OVER THE NC MTNS. THIS MEANS SNOW

WILL BE POSSIBLE MON NITE INTO TUE. HOWEVER...IT IS STILL WAY TOO

EARLY TO CONSIDER AMOUNTS GIVEN THE FLUX IN FCST SOLNS. LOWS WELL

ABOVE NORMAL SAT NITE FALL A LITTLE BELOW NORMAL BY MON NITE. HIGHS

NEAR TO A LITTLE ABOVE NORMAL SUNDAY FALL TO AROUND 10 DEGREES BELOW

NORMAL BY TUE.

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ATL_Militarypolice

ATL_Militarypolice

Posted
Posted

Low tracks practically right down 85...of course looks way too warm but it sure would be a lot of rain.

Plenty of rain to go around for everyone! :maprain:

gfs_namer_228_precip_ptot.gif

I have a feeling this is going to be a fun one to track. Great storm to see how the models handle this system, and find any bias they might have as we head towards winter.

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burgertime

burgertime

Posted
Posted

Plenty of rain to go around for everyone! :maprain:

I have a feeling this is going to be a fun one to track. Great storm to see how the models handle this system, and find any bias they might have as we head towards winter.

The 00z will be an interesting run to watch for next week. Does it maintain the SE trend with that low? Does the Euro slowly follow suit? 18z was a pretty odd run that's for sure but with the pattern like the experts have said anything is on the table.

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WeatherNC

WeatherNC

Posted
Posted

HPC extended disco from this afternoon

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

103 PM EST TUE NOV 22 2011

VALID 12Z FRI NOV 25 2011 - 12Z TUE NOV 29 2011

RECENT MODEL RUNS HAVE BEEN INSISTENT THAT AS A COLD GLFAK VORTEX

SETTLES IN THAT PACIFIC WAVE ENERGY WILL APPROACH THE WEST COAST

AS MORE OF A FULL LATITUDE TROF INSTEAD OF THE PRIOR WEEKS OF NERN

PACFIC SHORTWAVES THAT SLID DOWN THE WEST COAST AND ROTATED

INLAND. NEARLY ALL GUIDANCE TO VARYING DEGREES INDICATES A

BUILDING EPAC/WEST COAST RIDGE WHICH ALLOWS ADDITIONAL NRN STREAM

ENERGY TO DRIVE SOUTHWARD AND PHASE WITH THE SRN STREAM SHORTWAVE

COMING OUT OF THE BASE OF THE PAC TROF INTO THE SOUTHWEST AND

EVOLVE INTO A DEEP MID LEVEL TROF AS IT CLEAR THE ROCKIES AND

STRONGLY SHARPENS IN THE MS VALLEY. BY LATE WEEKEND AND EARLY NEXT

WEEK ALL DETERMINISTIC MODELS GFS/CMC/UKMET/NOGAPS/ECMWF HAVE AND

CONTINUE TO INDICATE A CUTTING OFF OF THE TROF INTO A VERY

SIGNIFICANT CUTOFF LOW. THE GFS SERIES HAS BEEN THE MOST

CONSISTENT WITH THE ECMWF BEING THE MOST ERRATIC WITH THIS

EVOLUTION FROM RUN TO RUN. ENSEMBLES OF GFS AND ECMWF HAVE BEEN

SHOWING A MORE PROGRESSIVE NATURE TO THIS SYSTEM WHICH ADDS TO THE

UNCERTAINTY BUT WITH THE PERSISTENCE OF DETERMINISTIC MODELS

INDICATING AN ANOMALOUS SOLUTION AND HEAVIER WEIGHTING TOWARDS

THAT TREND NEEDS TO BE ADDED. MINI MODEL ENSEMBLE/LAGGED AVERAGE

FORECAST OF GFS/ECMWF INDICATES A CLOSING OFF OF THE MID LEVEL

CENTER IN THE CENTRAL MS/LOWER OH VALLEYS LATE DAY 5 INTO DAY 7

SUN/TUES. MODELS USUALLY HAVE CONSIDERABLE DIFFICULTY HANDLING THE

EVOLUTION OF AND MOVEMENT/LOCATION OF CUTOFF LOWS AND CONFIDENCE

IS LOWERED BY DAYS 6 AND 7 MON/TUES. HPC UPDATED MORNING PROG

BLEND USES A BLEND OF OPERATIONAL 00Z CMC/GFS/ECMWF.

12Z GFS CONSISTENT WITH ITS IDEA OF A STRONG CLOSED/CUTOFF LOW

MID/LATE PERIOD. LATEST 12 CMC IS FASTER TAKING OUT THE MID LEVEL

TROF AND CLOSED LOW INTO THE UPPER OH VALLEY DAY 6 MON WHILE

AWAITING ANOTHER STRONG DIGGING TROF DAY 7 TUES AS DOES THE GFS.

12Z UKMET IS ALSO MORE PROGRESSIVE WITH FULL LATUITDE DEEP AND

SHARP TROF INTO THE APPLCHNS DAY 6. NOGAPS CONSISTENT WITH ITS MID

LEVEL CUTOFF

IN/OH DAY 7 TUES. EACH MODEL RUN UNTIL MUCH CLOSER IN WILL OFFER A

DIFFERENT LOCATION OF THE MID LEVEL CENTER AND DETAILS. SINCE THE

PRIOR HPC BLEND WAS MULTI MODELED SEE NO REASON TO CHANGE AT THIS

TIME FOR AFTN FINALS.

FAIR AGREEMENT OF THE NEXT PACIFIC TROF COMING INTO THE PAC

NORTHWEST AND NRN ROCKIES LATE SUN AND MON. ECMWF IS QUITE STRONG

WITH ANOTHER SHORTWAVE COMING INTO THE PACIFIC NORTHWEST BY TUES

WITH ITS ENS MEAN AND CMC MUCH MORE DAMPENED AND NON EXISTENT IN

THE GFS SOLUTION. THIS IS ALSO SUPRESSED BY THE HPC BLEND.

SRN STREAM SHORTWAVE WILL SPREAD RAIN ACROSS NWRN MEXICO INTO

NM/TX AND OK FRI WHILE NRN STREAM ENERGY WILL KEEP THE PACIFIC

NORTHWEST AND NRN ROCKIES WET. SHARPENING OF THE MID LEVEL TROF AS

PHASING OCCURS WILL BACK THE MID LEVEL FLOW AND ALLOW DEEP GULF

MOISTURE AND HVY PCPN TO SURGE NWD THRU EAST TX/OK/AR/MO AND UP

WELL NORTH INTO THE MS VALLEY SAT AND SUN. THIS WILL SPREAD

EASTWARD INTO THE APPLCHNS MON AND INTO THE MID ATLC COASTAL PLAIN

AND NORTHEAST BY TUES. COLD RAIN UNDER THE MID LEVEL CENTER IN THE

OH VALLEY/APPLCHNS WITH MID/LOWER LEVEL TEMPERATURES POTENTIALLY

COLD ENOUGH FOR HIGHER AND EVEN LOWER ELEV SNOW IN THE CENTRAL AND

SRN APPCHNS/UPPER OH VALLEY EARLY NEXT WEEK WITH SNOW POSSIBLE

ALONG THE WESTERN PORTION OF THE CIRCULATION IN THE MS VALLEY AND

PLAINS. HEAVY RAIN POTENTIAL EASTWARD ALONG THE SLOW MOVING

NEGATIVELY TILTED FRONT FROM THE SRN APPCHNS INTO PA. MDT TO

LOCALLY RAINS POSSIBLY UP ALONG THE ATLC SEABOARD AND INTO THE

PIEDMONT AND FOOTHILLS FROM GA INTO NEW ENGLAND MON INTO TUES.

LOCATION AND TRACK OF THE H500 MID LEVEL LOW ALONG WITH

ACCOMPANYING H850 COLD POOL MAY BECOME VERY CRITICAL ESPECIALLY

OVER HIGHER TERRAIN OF THE APPLCHNS.

ROSENSTEIN

HPC model disco from this afternoon (abridged)

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

137 PM EST TUE NOV 22 2011

VALID NOV 22/1200 UTC THRU NOV 26/0000 UTC

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR

INGEST...

FINAL 12Z MODEL EVALUATION INCLUDING THE ECMWF

ANY INITIALIZATION ERRORS WITH THE MODELS NOT APPEAR TO

SIGNIFICANTLY IMPACT THEIR SOLUTIONS.

...TROUGH SPLITTING ALONG THE WEST COAST DAY 2...

PREFERENCE:GFS/GEFS MEAN/NAM/ECMWF IN THE NRN STREAM

GEFS MEAN/NAM IN THE SRN STREAM

IN THE NRN STREAM...CONFIDENCE IS BELOW

AVG.

IN THE SRN STREAM...CONFIDENCE IS BELOW

AVG.

...STRONG FRONT ENTERING THE PACIFIC NORTHWEST LATE DAY2/EARLY DAY

3...

PREFERENCE: GEFS AND EC MEANS/NAM

...CONFIDENCE IS BELOW AVG.

all major players :whistle:

cor_day6_HGT_P500_G2NHX_00Z.png

18z gfs throwing snow around New Orleans?

post-382-0-16905700-1322002569.jpg

:huh:

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burgertime

burgertime

Posted
Posted

This is not a run-of-the-mill upper level low, very different from the 536dm bowling ball we saw a couple years back, aka Foothill Mauler. Based on what I am seeing, and I am sure others, this is a almost textbook full-latitude upper air trough going closed low, possibly into the sub 200mb layer, over the TN Valley. Any secondary low that forms will have to be watched closely through the SE, as any clearing would likely result in one of the more active late season svr wx outbreaks we have seen in recent memory. Met fall going out with a bang, 2011, go figure, not surprised... :popcorn:

Great write up as always! Thanks! thumbsupsmileyanim.gif

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Cold Rain

Cold Rain

Posted
Posted

I have a feeling that the extreme solutions that some of the models are showing are not going to happen. I expect that there will be a cutoff, but it'll likely be farther north and west and not as deep and persistent as, say, the 18Z GFS. It seems like the models always show these really deep, slow-moving, deep SE cutoffs in the medium range, but they end up being weaker, more transient, and farther NW in reality. Nevertheless, I'd be fine being wrong here. I'd love to see the extreme come to pass. We'd have a lot of fun weather for sure. Anyway, it'll be fun to track! :popcorn:

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FoothillsNC

FoothillsNC

Posted
Posted

I don't know if I buy the extreme solution of the GFS yet, and I haven't looked at the other models yet. I've already kind of put my thoughts in the other thread though. But I will say a heavy wet snow is very possible on the northwest side of the closed low whereever that track is. If its closed off over Miss. then the heavy wet snow would occur in nw Miss, Ark and west Tn and Mo. bootheel. If it cuts off and spins more toward Ky or STL , then the heavy wet snow would be more toward Missouri and maybe northern Ark. Fun storm to follow again, and I'll re-iterate how amazing the pattern keeps returning into. There's still no end in sight to the madness either, but at some point I think we get into a more stable flow in December. I also think before that happens the odds are higher than usual that a massive really cold core storm occurs, which would reach blizzard proportions. No idea where yet, but I'm leaning the odds somewhere btwn the plains and Apps. It fits this pattern.

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