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January 31-February 2 Historic Winter Storm part 8


Hoosier

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL

651 AM CST TUE FEB 1 2011

DISCUSSION

419 AM CST

STORM STUFF (TODAY THROUGH WEDNESDAY)...

GORGEOUS/CLASSIC MID LATITUDE CYCLONE IS DEVELOPING OVER THE

SOUTHERN PLAINS THIS MORNING...WITH BLOSSOMING (PARDON THE PUN)

BAROCLINIC LEAF ON SATELLITE IMAGERY. RAPIDLY EXPANDING WARM

CONVEYOR BELT WITH REGIONAL WSR-88D MOSAIC SHOWING LARGE AREA OF

MODERATE TO HEAVY PRECIPITATION WITH EMBEDDED THUNDERSTORMS

SPREADING FROM OKLAHOMA AND ARKANSAS INTO SOUTHERN MISSOURI EARLY

THIS MORNING. AS CYCLONE CONTINUES TO LIFT NORTHEASTWARD OUT OF

THE SOUTHERN PLAINS TODAY LOOK FOR CONTINUED EXPANSION OF THE

MODERATE TO HEAVY PRECIPITATION WITH THE WARM CONVEYOR BELT TO

BEGIN SPREADING INTO SOUTHERN PORTIONS OF THE CWA BY AS EARLY AS

LATE MORNING...AND UP TO THE WISCONSIN BORDER BY MID AFTERNOON.

GIVEN THE EXPECTED EARLIER ARRIVAL TIMES OF THE SNOWFALL...HAVE

ADJUSTED THE START TIME OF THE BLIZZARD WARNING TO 11 AM SOUTHERN

COUNTIES TO BETTER COINCIDE WITH THE EXPECTED DETERIORATING

CONDITIONS.

PART ONE (ASSUMING THE PIDDLY SNOW WE SAW OVERNIGHT WAS PART ZERO)

OF THE STORM SHOULD BE LARGELY DRIVEN BY INTENSE WARM AIR

ADVECTION/ISENTROPIC ASCENT. SNOWFALL WILL LIKELY BECOME HEAVY AT

TIMES WITH SIGNIFICANT SNOWFALL EXPECTED TO HAVE ACCUMULATED

ALREADY BY MID EVENING. CERTAINLY POSSIBLE THAT WE COULD SEE A BIT

OF A WANING IN THE INTENSITY OF THE SNOWFALL FOR A TIME THIS

EVENING BEFORE RAMPING BACK UP BIG TIME LATE EVENING/OVERNIGHT

WHEN PART TWO STARTS.

PART TWO OF THE STORM WILL BE WITH INTENSIFYING TROWAL/DEFORMATION

ZONE TONIGHT. UPWARD VERTICAL VELOCITIES ARE FORECAST TO BE ALMOST

OFF THE CHARTS TONIGHT AS UPPER TROUGH CLOSES OFF INTO A

NEGATIVELY TILTED CLOSED/COMPACT MID LEVEL LOW AS IT LIFTS

NORTHEAST TOWARD SOUTHERN LAKE MICHIGAN BY EARLY WEDNESDAY

MORNING. ALL INDICATIONS ARE THAT VERY INTENSE SNOWFALL WILL

DEVELOP WITHIN THE DEFORMATION BAND WITH TREMENDOUSLY STRONG UPPER

LEVEL DIFLUENCE AND DIVERGENCE AHEAD OF THE DEEPENING CYCLONE.

FORECAST SOUNDINGS SUGGEST THAT VERY STEEP MID LEVEL LAPSE

(NEARING 8C/KM) ASSOCIATED WITH THE VERY COLD TEMPS ALOFT WILL

PROVIDE FOR SUFFICIENT INSTABILITY FOR EMBEDDED THUNDERSTORMS TO

DEVELOP WITHIN THE TROWAL...LEADING TO LOCALLY ENHANCED SNOWFALL

TOTALS. IN FACT...SEVERAL MODELS SUGGEST THAT MUCAPES OF 100-200

J/KG WILL DEVELOP WHICH MEANS WE COULD ACTUALLY SEE UPRIGHT

CONVECTION DEVELOP.

MODELS IN GOOD AGREEMENT ON THE TRACK OF THE 700MB LOW...WHICH

POINTS TOWARD THE HEAVIEST BAND OF SNOW LINING UP FROM

SOUTHWESTERN CWA NORTHEAST TO CHICAGO OR THE SOUTHERN SUBURBS.

HAVING SAID THAT...THE CONVECTIVE POTENTIAL TONIGHT REALLY THROWS

A WRENCH INTO PIN-POINTING THE EXACT LOCATION OF WHERE THE

HEAVIEST SNOW BAND WILL END UP SETTING UP. IN FACT...SNOWFALL

TOTALS WILL LIKELY BE QUITE VARIABLE GIVEN NOT ONLY THE CONVECTIVE

POTENTIAL BUT THE INHERENT DIFFICULTY IN MEASURING SEVERELY

DRIFTED SNOWFALL. QUITE POSSIBLE THAT THE BLOW-ABILITY OF THE

SNOWFALL MAY BE SOMEWHAT LIMITED BY HOW HEAVY/WET IT WILL BE...BUT

TOO HARD TO SAY AND WITH VSBYS FROM WIND WHIPPED FALLING SNOW

LIKELY TO BE SEVERELY REDUCED BLIZZARD WARNING LOOKS RIGHT ON

TARGET.

WITH 500MB/700MB LOW FORECAST TO TRACK FROM NEAR UIN TO AROUND GYY

AM QUITE CONCERNED THAT MID LEVEL DRY INTRUSION COULD RAP INTO THE

SOUTHEASTERN 1/3 TO 1/2 OF THE CWA...CUTTING SNOWFALL OFF BY

OVERNIGHT TONIGHT WITH A CHANGE TO SLEET POSSIBLE BEFORE FLOPPING

OVER TO FREEZING DRIZZLE. THIS IS GOING TO HAVE TO BE MORE OF A

NOWCAST ISSUE AND ONLY CHANGE TO GOING FORECAST WAS TO INTRODUCE

SLEET INTO THE GRIDS LATE TONIGHT FAR SOUTHERN COUNTIES.

FINALLY...HAVE UPGRADED TO A LAKESHORE FLOOD WARNING FOR ILLINOIS

LAKE SHORE COUNTIES. INTENSE NORTHEAST WINDS WILL RESULT IN WAVES

BUILDING TO 14-18FT WITH OCCASIONAL WAVES UP TO 25FT. THIS VERY

LARGE WAVES ARE EXPECTED TO BATTER/BEAT/SHRED ANY PANCAKE ICE THAT

IS ALONG THE SHORE AND ALLOW THE VERY LARGE WAVES TO RESULT IN

COASTAL FLOODING. LAKE WATER LEVELS ARE RUNNING 6-12 INCHES BELOW

AVERAGE...HOWEVER WITH 15FT+ WAVES THIS SHOULD BE OF LITTLE

CONSEQUENCE. IN ADDITION TO COASTAL FLOODING...THE INTENSE WINDS

WILL RESULT IN HEAVY FREEZING SPRAY RIGHT NEAR THE LAKE COATING

EVERYTHING WITH A LAYER OF ICE.

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Negative. This thing will likely occlude than stall--similar to the Northern Plains bomb before tracking eastward.

lol, when then that's good news. Not really seeing it in the models though. They seem to blasting their precip fields east quickly. But I suppose that's a byproduct of them not handling the development of low pressure system itself very well.

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lol, when then that's good news. Not really seeing it in the models though. They seem to blasting their precip fields east quickly. But I suppose that's a byproduct of them not handling the development of low pressure system itself very well.

NCEP guidance is in epic fail mode, yes. Hopefully 12Z will catch on--doubt they will tho.

RGEM is doing pretty decent as is high res WRF guidance.

As you have been reading don't bother with the NCEP guidance and what they show. DVN laid it out nice in their disco.

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I've been reading this a lot from members. To me it seems if the low occludes faster it'll promote a transfer to the coast faster, thus reducing the duration of deformation zone precipitation over an area.

It will be hard to transfer too fast from that far west of the coast me thinks.

Just hoping i can avoid the dryslot that LOT hints at. I think i'm safe but who knows :arrowhead:

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Repasting the disco from DVN because it is too epic.

They said it better than I.

AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL704 AM CST TUE FEB 1 2011.UPDATE...

VERIFICATION AT 12Z INDICATES STORM SYSTEM IS RAPIDLY INTENSIFYING AT A RATE AS FAST OR FASTER THAN PROJECTIONS. COMPARING DATA...PLUS USING NUMEROUS TECHNIQUES SUGGESTS THE SYSTEM MAY NOT ONLY BE STRONGER...BUT COULD OCCLUDE OR WRAP UP MORE THAN PLANNED BACK TOWARD OUR AREA. IF THIS OCCURS...THIS COULD RESULT IN EVEN HIGHERSNOW TOTALS...SNOW-FALL RATES AND POSSIBLE THUNDER-SNOW OVER ATLEAST THE SOUTHEAST PORTIONS OF THE AREA. IT ALSO MAY RESULT INSLIGHTLY HIGHER WIND SPEEDS FOR MORE SEVERE BLIZZARD CONDITIONS.THIS RISK SHOULD BE CONFIRMED IN THE NEXT 3 TO 6 HOURS.NO CHANGES ARE PLANNED...BUT INDICATIONS CLEARLY SUPPORT THIS WILLNOT ONLY BE A MAJOR STORM OF NEAR HISTORIC PROPORTIONS...BUT MAYBE A BIT STRONGER FOR AT LEAST OUR SE 1/2 LOCATIONS THAN IS CURRENTLYFORECASTED.INDIVIDUALS SHOULD MONITOR THIS SITUATION FOR POSSIBLE UPDATES ONTHIS POTENTIALLY DANGEROUS SITUATION.

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not that I'm worried yet about the dry slot here but this thing would have to start moving a bit more east at this point or it would come close to here..

I think the dryslut will be making an appearance in LOTs area, just hope we can keep it south of I88.

latest hi-res arw and nmm drop close to 2" here.

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It will be hard to transfer too fast from that far west of the coast me thinks.

Just hoping i can avoid the dryslot that LOT hints at. I think i'm safe but who knows :arrowhead:

I would have thought so too but the sfc low kind of has the E-W enlongated look to it, like it's on a conveyor belt. RGEM which is apparently handling the system best has a 995 just SE of SPI at 6z Wed. 24 hours later it's off the coast of the Canadian Maritimes. Seems a little different then the octobomb situation where the low just sat and spun. But I'll take b_i's word over the RGEM. :lol:

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I would have thought so too but the sfc low kind of has the E-W enlongated look to it, like it's on a conveyor belt. RGEM which is apparently handling the system best has a 995 just SE of SPI at 6z Wed. 24 hours later it's off the coast of the Canadian Maritimes. Seems a little different then the octobomb situation where the low just sat and spun. But I'll take b_i's word over the RGEM. :lol:

I meant the northern plains blizzard--not octobomb. My mistake on wording.

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First time ever Chicago and St Louis in a blizzard warning at the same time?

It is indeed the very first blizzard warning ever issued for the STL metropolitan area. Definently one for the record books. The snow totals were upped in STL to 14-19 inches. Incredible storm, the low has dipped to under 1000mb as well. One for the record books.

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I know I've been ragging on the NAM pretty hard here, but I don't think NWP was truly meant/expected to handle situations like this (recall the last two that did this). They certainly hinted pretty well, but the 1-in-50 year beast is typically something that will run away from NWP since our parameterizations are certainly "breakable" at this level. Having said that, some of the meso-guidance is doing a pretty bang-up job so far.

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I know I've been ragging on the NAM pretty hard here, but I don't think NWP was truly meant/expected to handle situations like this (recall the last two that did this). They certainly hinted pretty well, but the 1-in-50 year beast is typically something that will run away from NWP since our parameterizations are certainly "breakable" at this level. Having said that, some of the meso-guidance is doing a pretty bang-up job so far.

Glad we didn't budge when we saw the cruddy 0Z stuff. I knew this had potential to go positive feedback bust with the convective driven pressure falls and extreme jet coupling aloft--but even I didn't think it would bomb this fast.

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