591
FXUS02 KWBC 061854
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
153 PM EST FRI NOV 06 2009
VALID 12Z MON NOV 09 2009 - 12Z FRI NOV 13 2009
NERN PAC TROF ENERGY IS FCST TO PROGRESS INTO NORTH AMERICA DURING
THE MEDIUM RANGE PERIOD. THE 00Z GEFS AND ECMWF/CANADIAN
ENSEMBLES SHOW SOME SPREAD/A FEW MEMBER OUTLIERS BUT BY DAY 7 FRI
THEIR MEANS GENERALLY AGREE IN SHOWING A POSITIVELY TILTED TROF
EXTENDING FROM NEAR CNTRL CANADA INTO THE SWRN CONUS. THE 00Z GFS
AND ECMWF DIFFER FROM THE ENSEMBLE MEAN CONSENSUS BY SEPARATING
NRN AND SRN STREAM FLOW... YIELDING AN ONTARIO/NRN CONUS SHRTWV BY
EARLY FRI AND A SEPARATE TROF OVER THE SOUTHWEST. PRIOR ECMWF
RUNS GENERALLY DID NOT SHOW THE DEGREE OF SEPARATION DISPLAYED BY
THE 00Z ECMWF/GFS OR AT LEAST WERE SLOWER WITH THE NRN PART OF THE
MEAN TROF... WHILE INDIVIDUAL GFS RUNS HAVE BEEN SOMEWHAT
INCONSISTENT WITH DETAILS. TELECONNECTIONS RELATIVE TO A CORE OF
NEGATIVE HGT ANOMALIES SETTLING OVER THE AK MAINLAND BY D+8... AND
POSITIVE ANOMALIES OVER THE NWRN PAC... OFFER SUPPORT FOR SOME
DEGREE OF FLOW SEPARATION OVER NOAM. HOWEVER SINCE THE NWRN
PAC/AK PATTERN IS ACHIEVED ONLY BY THE END OF THE PERIOD IT COULD
STILL TAKE A LITTLE TIME FOR THE TELECONNECTION FAVORED FLOW TO
EVOLVE DOWNSTREAM. TELECONNECTION CONSIDERATIONS ALONG WITH LACK
OF PRONOUNCED CONTINUITY WITH THE 00Z GFS/ECMWF SCENARIO FAVOR A
COMPROMISE BETWEEN THE GFS/ECMWF AND ENSEMBLE MEAN CLUSTERS.
FARTHER EWD THE GFS/ECMWF/UKMET ALL INDICATE THAT MID LVL ENERGY
OVER CNTRL NOAM AS OF DAY 3 MON MAY CLOSE OFF A FAIRLY VIGOROUS
CLOSED LOW OVER/NEAR THE NORTHEAST BY MIDWEEK WHILE THE CANADIAN
IS MORE SHEARED. RUN TO RUN CONTINUITY IN OPERATIONAL MODELS HAS
YET TO STABILIZE... ENSEMBLES FAVOR MAINTAINING A PROGRESSIVE
TROF... AND THE RECENT/CURRENT REGIME HAS BEEN FAIRLY PROGRESSIVE.
THUS IT APPEARS BEST TO LEAN SOMEWHAT FASTER/WEAKER THAN THE 00Z
GFS/ECMWF AT THIS TIME BUT NOT TO THE EXTENT OF THE ENSEMBLE
MEANS.
CURRENT T.D. IDA IS EXPECTED TO STRENGTHEN TO TROPICAL STORM
STATUS AS IT TRACKS INTO THE GULF OF MEXICO FROM THE NWRN
CARIBBEAN DURING THE SHORT RANGE PERIOD. MANUAL FORECAST
REPRESENTS TRACK POINTS FROM THE 15Z TPC ADVISORY...WITH WEAKENED
HPC/TPC COORDINATED DAYS 5-7 EXTRATROPICAL LOW POSITIONS
CONSISTENT WITH EXPECTED INCREASED SHEAR AND COOLER WATER
TEMPS...AND HELD IN PLACE IN LUE OF SIGNIFICANT MODEL
TRACK/STRENGTH UNCERTAINTY.
IN ORDER TO ACCOMMODATE THE ABOVE CONSIDERATIONS... AND ACCOUNTING
FOR THE ECMWF COMPARING SOMEWHAT BETTER TO THE FULL ARRAY OF
GUIDANCE THAN THE GFS... THE DAYS 3-7 MON-FRI FCST STARTS WITH A
BLEND OF THE 00Z ECMWF AND GEFS/ECMWF ENSEMBLE MEANS. SLIGHTLY
MORE WEIGHT WAS GIVEN TO THE ECMWF DAYS 3-4 BEFORE OPERATIONAL
DETAILS BECOME MORE UNCERTAIN. WE SEE NO COMPELLING REASON TO
ADJUST HPC CONTINUITY FOR OUR FINAL PRODUCTS CONSIDERING THE WIDE
ARRAY OF FORECAST SOLUTIONS STILL PROVIDED BY LATEST 12 UTC MODELS
AND ENSEMBLES.
RAUSCH/SCHICHTEL
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