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January 31-February 2 Historic Winter Storm part 6


Hoosier

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the one thing im concerned about for southern ontario is the possibility of a rapid occlusion that models are leaning towards now.....that could result in lower qpf amounts as the energy translates eastwards quicker......that could leave the region between say london ontario and the western hudson valley in a relative precip min.

i think thats what we have been seeing on the euro cutting back qpf, and even the GEM at 12z suggest it.

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Updated HPC model diagnostic discussion (including the 12z Euro).

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

138 PM EST SUN JAN 30 2011

VALID JAN 30/1200 UTC THRU FEB 03/0000 UTC

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

INGEST...

12Z MODEL EVALUATION INCLUDING THE ECMWF AND FINAL PREFERENCES

...SHORTWAVE TROUGH OVER SOUTHWESTERN CANADA...

PREFERENCE: GFS OR ECMWF

MODELS AGREE THAT THE TROUGH WILL PROGRESS INTO THE NORTHERN

ROCKIES/PLAINS BEFORE DISSIPATING. HOWEVER...THE NAM LIES NEAR THE

STRONG EDGE OF THE GUIDANCE DURING THIS PROCESS...WHICH MAY BE A

RESULT OF INITIALIZING THE TROUGH APPROXIMATELY 50-75 NM EAST OF

ACTUAL POSITION. OTHERWISE...THE GFS INITIALIZES THE TROUGH BETTER

THAN THE NAM AND AGREES WITH NON-NCEP GUIDANCE. THUS...RECOMMEND

EXCLUDING THE STRONGER NAM.

...UPPER LOW FORMING OVER THE INTERMOUNTAIN WEST/ROCKIES THROUGH

THE PERIOD...

PREFERENCE: AFTER 00Z TUE...ABOUT MIDWAY BETWEEN THE NAM/ECMWF

THE NEW ECMWF HAS TRENDED SLIGHTLY WEAKER AND NORTH OF ITS PRIOR

RUN BY 60-84 HRS AND MERGES NICELY WITH THE NAM/UKMET...WHICH

PLACES THE GFS WITHIN THE NORTHEAST HALF TO ONE THIRD OF ALL

GUIDANCE BY 84 HRS. THUS...GIVEN ITS POSITION WITHIN THE GUIDANCE

ENVELOPE AND CLUSTERING OF OTHER AVAILABLE GUIDANCE...RECOMMEND

LESS OF THE GFS LATER IN THE PERIOD.

...UPPER LOW MOVING FROM N. CA TO THE S. PLAINS AND OH VALLEY

THROUGH THE PERIOD...

...LOW PRESSURE MOVING TX TO THE OH VALLEY TUE-WED...

PREFERENCE: BEFORE 00Z WED...EQUAL BLEND GFS/ECMWF

AFTER 00Z WED...2/3 GFS TO 1/3 NAM

THE NAM SHOWS SUSPICIOUS LOW AND MID LEVEL AMPLIFICATION CROSSING

CALIFORNIA TODAY WHICH APPEARS AT LEAST IN PART DUE TO CONVECTIVE

GRID-SCALE FEEDBACK. ADDITIONALLY...

ACCORDING TO WATER VAPOR IMAGERY AND COMPARISONS WITH OTHER MODEL

GUIDANCE...THE NAM INITIALIZES THE CENTER OF THE TROUGH ABOUT 50

NM WEST OF ITS ACTUAL POSITION WHICH CONTRIBUTES TO ITS

SLOWER/DEEPER SOLUTION CROSSING THE ROCKIES AND PLAINS BEFORE

EVENTUALLY MERGING WITH THE GFS. MEANWHILE...THE NEW ECMWF HAS

TRENDED SLOWER ENTERING THE PLAINS/MIDWEST AND SLIGHTLY STRONGER

WITH THE PARENT SURFACE LOW ENTERING THE OH VALLEY...WHICH

SUPPORTS THE GFS SOLUTION. THUS...EARLIER PREFERENCES REMAIN

INTACT...WITH AN EQUAL BLEND OF THE GFS/ECMWF PREFERRED DAYS

1/2...BEFORE ABANDONING THE ECMWF IN FAVOR A GFS/NAM BLEND FOR DAY 3.

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the one thing im concerned about for southern ontario is the possibility of a rapid occlusion that models are leaning towards now.....that could result in lower qpf amounts as the energy translates eastwards quicker......that could leave the region between say london ontario and the western hudson valley in a relative precip min.

i think thats what we have been seeing on the euro cutting back qpf, and even the GEM at 12z suggest it.

Yeah--with the stronger wave aloft and the overall stronger surface low--that is a reality for some locations now. More intense but with a rapid occlusion.

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Wish his blog mentioned how he came up with those numbers.

I believe he's mentioned using mathematical equations to his forecasting before. Whatever that means. Regardless, his snowfall totals for here are way too much. But he does say that further adjustments may be necessary.

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IND's new zones are out and they mention absolutely no plain rain anywhere North of 70. Good call IMO.

I like LAF for Tuesday night. Not sure I buy the heavy snow part at this point

TUESDAY NIGHT...WINDY. FREEZING RAIN AND LIGHT SLEET THEN SNOW AFTER MIDNIGHT. HEAVY SNOW ACCUMULATIONS. SIGNIFICANT ICE ACCUMULATION POSSIBLE. NEARLY STEADY TEMPERATURES IN THE LOWER 20S. NORTHEAST WINDS 25 TO 30 MPH. CHANCE OF PRECIPITATION NEAR 100 PERCENT.

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I like LAF for Tuesday night. Not sure I buy the heavy snow part at this point

TUESDAY NIGHT...WINDY. FREEZING RAIN AND LIGHT SLEET THEN SNOW AFTER MIDNIGHT. HEAVY SNOW ACCUMULATIONS. SIGNIFICANT ICE ACCUMULATION POSSIBLE. NEARLY STEADY TEMPERATURES IN THE LOWER 20S. NORTHEAST WINDS 25 TO 30 MPH. CHANCE OF PRECIPITATION NEAR 100 PERCENT.

I'm jealous. I get an 1-2" Tuesday night.

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This storm is just going to be something epic. Honestly in my 3.5 years of being an actual met I have never seen a storm of this intensity, magnitude, and impact across this part of the country. Granted--not a long time--but still. This storm will have major impacts. Kudos to the NWS for getting early warning out. Nobody should be surprised.

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