EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
120 PM EST FRI NOV 17 2006
VALID 12Z MON NOV 20 2006 - 12Z FRI NOV 24 2006
...STRONG COASTAL STORM TO AFFECT THE MID ATLANTIC AND
SOUTHEASTERN SEABOARD THROUGH MUCH OF THANKSGIVING WEEK...
EASTWARD...
THERE REMAINS UNCERTAINTY ON THE DETAILS WITH THE CUT OFF LOW OVER
THE SOUTHEAST...BUT WITH THE MODELS IN DECENT AGREEMENT THRU DAY
4/TUES...CONFIDENCE IS INCREASED. THE GFS CONTINUES TO BE THE
DEEPEST SOLN WHILE THE ECMWF CONTINUES TO BE MORE SWLY BY DAY
5/WED. BOTH THE GFS AND ECMWF REMAINED TOO PHASED AND NLY INTO
THEIR FORECAST PDS WITH THE LAST TWO CUT OFF LOWS E OF THE MS
RVR...GENERALLY NOT PICKING UP ON THE GENERALLY PSN OF THE H5 LOW
UNTIL 3 DAYS OUT. THE ECMWF IS FASTER TO CUT OFF THE LOW THAN THE
GFS BUT IS MORE NLY WITH ITS PSN EARLY IN THE PD. GIVEN THE PAST
PERFORMANCE...WILL LEAN TOWARD A MORE SLY H5 LOW LIKE THE GFS
EARLY IN THE PD...BUT THE GFS HOLDS ONTO A HIGHLY AMPLIFIED AND
SLOWER NRN STREAM TROF OVER THE NORTHEAST DAYS 4/TUES AND 5/WED
WHICH IT DID YESTERDAY AND IS AN OUTLIER SOLUTION.
OVERALL...ECMWF WITH SOME SMALL PERCENTAGE OF GFS ADDED SERN
SEABORD LOW. AFTER DAY 6 THE MORE WLY DRIFT OF 00Z ECMWF HAS FEW
FRIENDS...SOME OF ITS ENSEMBLES. 00Z CANADIAN POSITIONING IS
BETWEEN THE 00Z GFS AND AND THE 00Z ECMWF. HPC PROGS ARE A
COMPROMISE BETWEEN THOSE THREE MODELS.
MODEL FORECAST STANDARD DEVIATIONS ARE IN THE EXTREME RANGE FROM
BOTH THE 00Z RUNS GFS AND ECMWF WITH VERY LOW HTS AT LOW LATITUDES
WITH NUMBERS RANGES 6 POSSIBILTY 7 BELOW NORMAL OVER SRN FL WITH
THIS CLOSED/CUTOFF MID LEVEL LOW.
THIS WILL BE A VERY SIGNIFICANT WEATHER MAKER THIS WEEK FOR THE
ATLC SEABOARD AND WRN ATLC. ONSHORE GALE TO NEAR STORM FORCE WINDS
FROM THE DELMARVA INTO FL TUE-THU AND WITH A CONTD LINGER ALONG
THE MID ATLC COAST INTO FRI. A HVY RAIN THREAT FROM THE OUTER
BANKS TO NERN FL TUE/WED SPREADING NWD INTO VA/MD/DE/NJ AND
POSSIBLY AS FAR N AS SRN NEW ENG LATE THURS AND FRI. PROLONGED
PERIOD OF ONSHORE GALE WINDS ENHANCED BY A FAVORABLE SPRING TIDAL
LUNAR CYCLE WILL BRING ABOVE NORMAL TIDES AND BEACH EROSION AND
TIDAL FLOODING FOR SEVERAL DAYS MAINLY MID ATLC COAST...BUT VERY
POSSIBLY AFFECTING THE FL EAST COAST DEPENDING UPON THE SFC LOW
POSITION. PROLONGED PERIOD OF GALE TO STORM FORCE WINDS AGAINST
THE GULF STREAM FLOW WILL BE A MAJOR SHIPPING HAZARD THROUGH MUCH
OF THE WEEK. SEE OPC WARNINGS/DISCUSSIONS.
ELSW AWAY FROM THE COAST VERY COOL TEMPS CAN BE EXPECTED ACROSS
INLAND REGIONS FROM THE MID ATLC DEEP INTO FLORIDA TUES AND
WED...AS MUCH AS 15 BELOW NORMAL ACROSS FLORIDA AND REMAINING COOL
TOWARDS THE WEEKEND.
Source:
http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html