PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
723 AM EST SAT NOV 07 2009
 
VALID 12Z WED NOV 11 2009 - 12Z SAT NOV 14 2009
 
OVER THE PAST DAY MEDIUM RANGE GUIDANCE HAS BEEN CONSISTENT IN
BRINGING A DEEP CORE OF NEGATIVE HGT ANOMALIES OVER ALASKA BY THE
LATTER HALF OF THE PERIOD... WITH FAST FLOW PROGRESSING ACROSS THE
NRN PACIFIC.  TELECONNECTIONS RELATIVE TO THE NEGATIVE ANOMALY
CENTER OVER AK FAVOR SOME DEGREE OF FLOW SEPARATION OVER THE
CONUS/SRN CANADA WITH A MODEST MEAN TROF OVER THE WRN CONUS AND A
NRN STREAM MEAN TROF OVER ERN CANADA INTO THE GRTLKS AND VICINITY.
 INDIVIDUAL MODEL AND ENSEMBLE SOLNS CONTINUE TO SHOW A MODERATE
AMOUNT OF SPREAD AND SOME MEANINGFUL CONTINUITY CHANGES WITH
INDIVIDUAL FEATURES... BUT THE OVERALL AVERAGE OF GUIDANCE STILL
PROVIDES REASONABLE CONTINUITY.

REGARDING FLOW FROM THE PAC ACROSS NOAM... THE 00Z GFS IS FASTEST
AND/OR MOST AMPLIFIED WITH SHRTWV ENERGY REACHING THE NORTHWEST BY
DAY 7 SAT.  FAST NRN PAC FLOW AND RECENT TENDENCY FOR PROGRESSIVE
SOLNS TO TURN OUT BETTER THAN THE SLOW SIDE OF THE SPREAD WOULD
FAVOR FASTER TIMING THAN THE 00Z GEFS MEAN AND ESPECIALLY 12Z
CANADIAN ENSEMBLE MEAN.  HOWEVER THE TYPICALLY FAST GFS BIAS STILL
RECOMMENDS LEANING SOMEWHAT SLOWER TOWARD THE 00Z ECMWF/CMC AND
12Z ECMWF ENSEMBLE MEAN.  WITH ERN PAC FLOW PROGRESSING INLAND BY
MID-LATE WEEK... THE 00Z GFS IS ON THE FAST EDGE OF MODEL/ENSEMBLE
CONSENSUS AND BECOMES QUESTIONABLY AMPLIFIED WITH ITS TROF THAT
REACHES ERN CANADA/NERN CONUS BY DAY 7 SAT.  THIS GFS TROF IS
STILL MOSTLY CONTAINED WITHIN THE FULL ENVELOPE OF 00Z GEFS
MEMBERS THOUGH.  THE GFS COMPARES MORE FAVORABLY TO THE
MODEL/ENSEMBLE SPREAD WITH TRAILING ENERGY OVER THE WEST BY
FRI-SAT.

OVER THE EAST... 00Z OPERATIONAL MODELS HAVE GENERALLY TRENDED
SOMEWHAT FASTER AND LESS CLOSED WITH MID LVL TROF ENERGY FCST TO
REACH THE EAST COAST BY DAY 4 WED... WITH THE 12Z ECMWF ENSEMBLE
MEAN FAIRLY CLOSE TO THE 00Z ECMWF/CMC.  THE GFS IS ONLY SLIGHTLY
FASTER WHILE THE GEFS MEAN APPEARS A LITTLE TOO FLAT/FAST IN LIGHT
OF CURRENT OPERATIONAL CLUSTERING.  MEANWHILE OVER THE GULF OF
MEXICO IDA IS EXPECTED TO BECOME EXTRATROPICAL BY AROUND DAY 4 WED
AS IT INTERACTS WITH AN APPROACHING FRONT.  THE MANUAL FCST
REFLECTS INTERPOLATION FROM THE 09Z TPC ADVISORY THRU DAY 4 WITH
THE REMAINDER OF THE FCST REFLECTING SLOW SUPPRESSION IN RESPONSE
TO HIGH PRESSURE BUILDING INTO THE EAST.  THERE IS SOME
UNCERTAINTY OVER WHAT PROPORTION OF THIS SYSTEM WILL REMAIN OVER
THE GULF VERSUS BEING CARRIED EWD INTO THE ATLC.

BASED ON THE ABOVE CONSIDERATIONS AND CONTINUITY... THE MEDIUM
RANGE FCST FOLLOWS A BLEND OF THE 00Z ECMWF AND 00Z GEFS/12Z ECMWF
ENSEMBLE MEANS WITH MINOR ADJUSTMENTS TO ACCOUNT FOR THE FCST FOR
IDA OVER THE GULF OF MEXICO. UPDATED PRELIM PROGS MAINTAIN HPC
CONTINUITY AFTER CONSIDERATION OF LATER 06Z GFS GUIDANCE THAT
ALONG WITH THE 00Z NOGAPS/UKMET ONLY INTRODUCES HIGHER SOLUTION
SPREAD/UNCERTAINTY WITH EMBEDDED SYSTEMS INCLUDING IDA.  THE 00
UTC ECMWF AND CANADIAN ENSEMBLES ARE ALSO UNAVAILABLE SO FAR
TODAY.

RAUSCH/SCHICHTEL