671
FXUS02 KWBC 311858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
257 PM EDT SAT OCT 31 2009
VALID 12Z TUE NOV 03 2009 - 12Z SAT NOV 07 2009
THE 06Z AND 12Z/31 GFS AND ENSEMBLE SPAGHETTI PLOTS SIMPLY
RE-ENFORCE THE THINKING OF THE EARLY PRELIM: EXPECT FAST SLIGHTLY
CYCLONIC FLOW ACROSS THE NRN TWO THIRDS OF THE CONUS... DOMINATED
BY THE MAIN POLAR JET. THE UKMET/CANADIAN ARE SHOWING SIGNS OF
FAVORING A FLAT WRN RIDGE/ERN TROF PATTERN THE LATTER PORTION OF
NEXT WEEK...HOWEVER THEIR PATTERN DIFFERS MARKEDLY FROM THAT OF
THE 00Z/31 ECMWF WHICH HAS MORE OF A BROAD TROF DEVELOPING OVER
SWRN CANADA.
THE GUIDANCE IS IN GENERAL AGREEMENT THAT RELATIVELY LOW LATITUDE
CLOSED CYCLONES WILL BE PRESENT TUE DAY 3 IN THE ERN PACIFIC AND
WRN ATLANTIC ...SEPARATED FROM A PROGRESSIVE AND RELATIVELY FLAT
FLOW PATTERN IN THE POLAR WESTERLIES. GUIDANCE IS STILL SHOWING
SIGNIFICANT DAY-TO-DAY CHANGES IN THE FORECAST FLOW PATTERN...BUT
WITH INCREASED SEPARATION OF THE SOUTHERN AND NORTHERN STREAMS OF
THE WESTERLIES...LARGE SCALE AMPLIFICATION IS NO LONGER
ANTICIPATED IN THE POLAR JET OVER NORTH AMERICA.
AN AVERAGE OF THE 00Z/31 ECMWF/GEFS/CANADIAN MODELS MEANS SEEMS
THE SAFEST BET FOR THE END OF NEXT WEEK AT THIS TIME. WE SHY AWAY
FROM MODEL AND ENSEMBLE SOLUTIONS THAT SHOW TOO MUCH SHORTWAVE
AMPLITUDE. THE POTENTIAL FOR LARGE SHORTWAVE TIMING ERRORS WILL BE
ABOVE NORMAL ESPECIALLY THU DAY 5 AND BEYOND. THE 12Z/31 CANADIAN
RUN SEEMS TO BE GOING FOR A PROGRESSIVE RIDGE OVER WRN NOAM
THU-FRI WITH TROFFING OVER THE OH VLY...BUT IT HAS BACKED OFF FROM
ITS 00Z/31 ERN CO VORT MAXIMUM IT HAD FOR NEXT FRI. THE NEW 12Z/31
UKMET ALSO IS SHOWING A TENDENCY FOR A BROAD WRN NOAM RIDGE/TROF
ALONG 80W BY FRI. THE NEW 12Z/31 ECMWF HAS ACTUALLY SWITCHED
TOWARDS MORE OF LAST NIGHTS CANADIAN TROF OVER ERN CO/WRN KS FOR
FRI DAY 6. LOW CONFIDENCE HERE.
FOR OUR FINALS...WE STAYED WITH OUR PRELIM 00Z CANADIAN/00Z GEFS
MEAN EARLY IN THE MEDIUM RANGE TRENDING TOWARDS A 00Z ECMWF/00Z
GEFS MEAN COMPROMISE BY THU/FRI. THE SENSIBLE WEATHER PATTERN WILL
BE QUIET AND SEASONABLY COOL OVER MUCH OF THE CONUS AFTER A VERY
ACTIVE OCTOBER FOR MUCH OF THE COUNTRY.
FLOOD
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