Nail Biting Time In the NE US

[Steve H.]

Ya just gotta love Drag's enthusiasm:
FXUS61 KBOX 071706
AFDBOX

AREA FORECAST DISCUSSION..UPDATED..
NATIONAL WEATHER SERVICE TAUNTON MA
1206 PM EST WED DEC 7 2005

...WE AWAIT FURTHER MULTIMODEL CONSENSUS BEFORE ANY ADJUSTMENTS
NCEP MODELS BOMBOGENESIS FRIDAY...

.SHORT TERM (THROUGH THURSDAY NIGHT)...
NO SIG CHANGES IN THE 11AM PACKAGE. WE'LL REREVIEW FOR SPOT WIND ADVY
CRITERIA LATER THIS AFTN-EVE IN STRENGHTENING CAA.

LATE DAY PKG WILL EXAMINE POSSIBLE LE SW- FOR CAPE COD LATE TONIGHT
OR THURSDAY MORNING AS BL FLOW TURNS MORE NLY WITH STEEP LAPSE LOW
LVL RATES. NAM IS FORMING CLOUDS OUT THERE BUT NO SW- ON THE NAM10
NOR SUSBMM5. PROBABLY TOO DRY AND STILL TOO MUCH CONTINENTAL FLOW IN
THE NEARBY CW TO ALLOW FOR SW- OUTER CAPE.

&&

.LONG TERM (FRIDAY THROUGH TUESDAY)...
WE HAVE SEEN THE 12Z OP VERSIONS OF THE NCEP NAM NGM GFS AS WELL AS
THE CANADIAN GGEM AND ENGLANDS UKMET.

NAM DEEPENS THE SFC LOW 28 MB IN 12 HRS AS IT TRACKS IDEALLY FOR A
MUCH OF INTERIOR SNE MDT SNOWSTORM (YES WE SAW THE NAM 1.5" BOS)...
BUT...NAM BL FLUX'S AND TYPICAL NW BIAS CONSIDERED...PLUS CLIMO AND
ONE HAS TO THINK ITS NOT RIGHT. HOW OFTEN DOES OUR REGION GET PASTED
WITH A FOOT OF SNOW IN A WINTER...ESPECIALLY FROM WHAT APPEARS TO BE
A SHORT WAVE THAT IS OPENING. AND DIDNT WE HAVE SOME PROBLEMS WITH
THIS JUST YESTERDAY? NOT MY MODEL OF CHOICE.

THE GFS DEEPENS 24 MB IN 12 HRS...BUT IS 2 DEGS FURTHER S ON ITS
SFC LOW AND THE 500 MB SHORT WAVE AT 60 HRS DIFFERS BTWN THE NAM/GFS
(FOR 00Z/SAT THE 10TH) WITH THE NAM FEEDBACK EXCITING 500MB
DEEPENING...WHILE THE GFS IS STEADY. I CAN LIVE WITH THIS BUT AM
SUSPICIOUS. WHY...SEE BELOW.

THE UKMET AND GGEM ARE SLOWER AND NOT AS VIGOROUS WITH THE DEEPENING
FRIDAY...DELAYING IT TILL ITS E THE BENCHMARK.

ALREADY BIG DIFFS SHOWING UP BETWEEN THE 12Z NAM NGM AND GFS AND EVEN
THE 12Z GGEM UKMET AND SUSBMM5 OP RUNS...ARD 5MB DIFFERENCE NEAR CAPE
MAY FOR 12Z FRI WITH THE NAM THE OUTLIER AND SUSPECT WRONG IN FAR TOO
MUCH DEEPENING THERE. IF THE NAM IS WRONG AGAIN ON THIS NWWD
EXTENSION...THE ENTIRE NAM PACKAGE IS A WRONG SIGNAL. ODDS FAVOR 12Z
GFS NGM GGEM UKMET COMBO. AND GGEM SUSBMM5 ARE ALSO SLOWER WITH SNOW
ONSET EARLY FRI...AS THE SUSBMM5.

WE ARE CURRENTLY MISSING THE ENSEMBLE PAGE FROM CTP WHOSE OFFICE MAY
BE INVOLVED IN A PHYSICAL MOVE BUT REVIEWED THE GFS POP TRENDS FOR
24 HR 1" AND 12 HR .60 EARLIER TODAY AND NOTED A SWD TREND IN THE
00Z/7 GFS ENS FROM THE 18Z/6 GFS ENS. THAT PLUS THE VERY SLOW TO
DEVELOP 00Z RUN OF THE ECMWF...HAVE TO TEMPER THE NAM IN LIEU OF
OTHER MODEL CONSENSUS...WHICH IN THE OPINION OF THIS FCSTR WHO MUST
FILE FORECASTS THAT VERIFY CLOSE TO REALITY...THE NAM IS FALLING
FURTHER BEHIND THE GFS ON DAY DAY PERFORMANCE.

THE 12Z GFS UKMET SUSBMM5 COMBO KEEPS THE SPS CRITERIA GOING... GGEM
IS SLIGHTLY FURTHER N ON ITS SIG QPF INTO SNE (A SLIGHTLY WARMER RUN)
WHICH ALSO JUSTIFIES PRIOR 24 HR SPS/SNOW KBOX FCST ISSUANCES.
HOWEVER THE GGEM UKMET COMBO ARE ABOUT 11MB WEAKER THAN THE GFS AND
14 MB WEAKER THAN THE NAM. THATS A PROBLEM!

EWD SPEED VARIES BUT FAIRLY CLOSE FOR 60 HRS (00Z/SAT).

IF THESE MODELS ARE OVERDOING THE SHARPNESS OF THE SHORTWAVE OR IT
RUNS FLATTER...WE'VE GOT A SWD BUST PROBLEM.

[Nimbus]

Doesn't look like much in the water vapor imagery yet.

[WindRunner]

That is an amazing discussion! I wish the people down in Sterling would write like that.

[Steve H.]

Yes, he shows you all the info available to him, the reasons for and against a particular scenario. Now the 12Z NAM and GFS are darn close as far as SNE is concerned, and IF the GFS were dead on I would say that the only areas in NY that could chage over or mix with rain would be eastern LI, and maybe the south shore, but should change back to snow after an hour or two. Western LI and NYC should stay all snow. It will be hard to scour out that cold air for that short a period, and I don't think that E/NE winds will bwe very strong at all til this bombs out near CC. However the NAM is much weaker and doesn't bomb it out like the GFS so we'll see what impact that has.