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Saturday, January 24, 2015

1-27 "clipper" or Miller B

1-27  From my facebook post
 I tried to demonstrate what your local meteorologists go through with a snow storm.  While they get the day to day and most storms correct, when there is a bust like this, its good to see what they were looking at and realize that with all the info out there, snowstorms are still really tricky.   With this one, the mid range models caught on late (Saturday), but did get the track of the storm mostly correct from there.  The precip field was wrong though.  The short term model (NAM) held off until Sunday then went nuts with precip, only to back off once or twice, and then last night at 7pm, backed off completely.  The real time models (HRRR/RAP) run 18 hours out, so they couldn't be used until yesterday.  They showed basically no precip for NNJ, Western CT, though did have it for NYC east and east of Bridgeport.   Models aside, the satellite looked good, and right before I went to sleep at midnight, it was snowing hard and the radar looked like it had a fire hose pointed right at NYC/Danbury.  But bands are hard to predict, and so was the sharp cutoff of precip.   Normally a 980mb low slowly moving over the 40/70 benchmark would yield 12-18 inches here, but it didn't.  So congrats to those east of Hartford and LaGuardia where 1 to 3 feet fell.  I'm up to 5.5" and wondering if that last band makes it here.

1-25
 Just got back home and checked on these two things first. QPF trends - NAM from 0z run to 12z run moved west and increased. 18z didn't shift east much with the bulk of the precip, but did lower the amounts. Next run may show a trend.






GFS 0z came to the party in Newark (1.21qpf ewr) , 6z GFS came with booze (1.57qpf), 12z left the party (.94) and the 18z drove away(.92). So there is something to watch.






Second - SREFs. Compare the 15z with each run before and watch the spread lessen, but amounts increase. This is good (at least for Oxford)
15z - lowest member 7", range 7"-30" but only 1 member under 15"


9z 1" to 43" 5 membs

3z range 2" to 30"

JMA seems onboard
CMC has a bit of a different approach, but still produces alot



NWS Upton AFD
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
     A LIFE THREATENING...HISTORIC WINTER STORM EXPECTED FROM LATE
MONDAY INTO TUESDAY...

NWP GUIDANCE CONTINUES TO BRING THE INGREDIENTS TOGETHER FOR A
DANGEROUS...HISTORIC BLIZZARD AS A SECONDARY LOW FORMS OFF THE
MID ATLANTIC COAST ON MON. THIS LOW WILL UNDERGO RAPID
INTENSIFICATION AS THE PARENT UPPER LOW CUTS OFF ALOFT NEAR THE
MID ATLANTIC MON NIGHT...STALLING SE OF MONTAUK LATE MON NIGHT
INTO TUE. MSLP DROPS NEARLY 30 MB IN 24 HR FROM MON AM TO TUE
AM... BEFORE GRADUALLY FILLING.

THIS WILL PLACE THE FORECAST AREA ON THE NW FLANK OF THE
LOW. AFTER LIGHT WARM ADVECTION SNOWFALL OF 1-3 INCHES DURING THE
DAYTIME HOURS MON IN ADVANCE OF THE SECONDARY LOW...A PROLONGED
PERIOD OF MDT-HVY SNOW EXPECTED IN THE DEFORMATION ZONE.
FOLLOWED 12Z NAM/ECMWF CLOSELY...WITH BOTH MODELS SUPPORTING QPF
UPWARDS OF 2 INCHES LIQUID EQUIVALENT...WITH THE HIGHEST AMOUNTS
NOW EXPECTED NOT ONLY ACROSS ERN LONG ISLAND/CT BUT ALSO FARTHER
WEST INTO SW CT AND THE NYC METRO AREA/WESTERN LONG ISLAND...AS
MODELS OFTEN DO NOT PLACE THE AREA OF MOST INTENSE MID LEVEL
FRONTOGENESIS FAR ENOUGH WEST. SNOWFALL RATES OF 2-4 INCHES PER
HOUR EXPECTED LATE MON NIGHT INTO TUE MORNING. MUCH OF THE AREA
SHOULD SEE AMOUNTS OF 20-30 INCHES...LOCALLY HIGHER WHERE BEST
MESOSCALE SNOW BANDING SETS UP.

IN ADDITION...THE DEEP LOW PRESSURE COMBINED WITH STRONG HIGH
PRESSURE TO THE NORTH AND WEST AND HEAVY FALLING/BLOWING SNOW WILL
CREATE BLIZZARD CONDITIONS ACROSS THE ENTIRE REGION. A BLIZZARD
WARNING IS NOW IN EFFECT...WITH POTENTIAL FOR SUSTAINED WINDS UP
TO 40 MPH ON LONG ISLAND...AND WIND GUSTS RANGING FROM 40 MPH
INLAND...TO 50-55 MPH MOST ELSEWHERE...TO 65 MPH ACROSS ERN LONG
ISLAND...WHERE A BRIEF HURRICANE FORCE GUST CANNOT BE RULED OUT.

TEMPS DURING THE STORM WILL GENERALLY BE IN THE 20S...EXCEPT
FALLING TO 15-20 MON NIGHT INLAND. WIND CHILLS WILL BE MOSTLY IN
THE SINGLE DIGITS TO MID TEENS...BUT AS LOW AS ZERO TO 5 BELOW
ACROSS SOUTHERN CT.

THANKS TO ALL NEIGHBORING WFOS...ERH AND WPC FOR COLLABORATION
THIS AFTERNOON.


 1-25 morning


1-24 afternoon
12z ukmet is on board too.  CMC has it, east, but its kinda loopy
SREF's for Oxford Airport


Euro bombs low to 980, upper low stacks over it just east of ACY.  The result is the snow map below

30+ inches 12z euro


1-24
Models have been pushing the clipper coming through further south - this has been the case all year and they usually have resulted in nothing or less than an inch.  I wrote this one off a few days back and have watched models push it south.  But now there seems to be some blocking, probably due to the current low.  Instead of the clipper going through S. IL, KY, VA/NC and out to sea, it bombs once off the coast and heads N just off the Cape (per Euro).  Actually looks like the trough goes negative, a 500mb low forms and stalls the LP as it deepens. Interestingly, its further out to sea than todays storm, but has the same amount of moisture - red flag.  With the qpf being .5-.75 per below map, and colder air and higher snow ratios, this should be another 6"+ storm. Don't see any mixing issues for anyone in NJ, NY, CT, RI

NAM agrees! No temp issues there either.  This qpf should be a foot or more.
12z GFS (as usual lately) is further east, but still impressive for E. Mass. Only puts .2" down for DXR.


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