593
FXUS02 KWBC 091827
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
227 PM EDT SUN AUG 09 2009
VALID 12Z WED AUG 12 2009 - 12Z SUN AUG 16 2009
A WELL ORGANIZED VORTEX NEAR THE SOUTHERN BERING SEA AND RESIDUAL
NEGATIVE HEIGHT ANOMALIES OVER THE GULF OF ALASKA FAVOR A
DOWNSTREAM LONGER WAVE FLOW PATTERN HIGHLIGHTED MID-CONTINENT
RIDGING SANDWICHED BY TROUGHS CENTERED NEAR THE PACIFIC NORTHWEST
COAST AS WELL AS ACROSS EASTERN CANADA. THIS IDEA FITS IN BEST
WITH YESTERDAYS 12 UTC ECMWF AND THE 00 UTC GEFS ENSEMBLE MEAN.
HOWEVER...THE 00 UTC GFS/ECMWF/CANADIAN FORM A STRONG CONSENSUS
TRENDING TOWARD A MORE INLAND AND DEEPER TROUGH PROGRESSION INTO
WESTERN NORTH AMERICA. TAKING THESE PLAUSIBLE FLOWS AND
UNCERTAINTY/SPREAD AND CONTINUITY INTO ACCOUNT...PRELIM AND FINAL
HPC MEDIUM RANGE PROGS REMAIN PRIMARILY DERIVED FROM A
COMPROMISE/BLEND OF THE 00 UTC GEFS MEAN AND 00 UTC ECMWF THROUGH
THE MEDIUM RANGE DAYS 3-7 FORECAST. WE SEE NO COMPELLING REASON
TO CHANGE HPC PREFERENCE/CONTINUITY AFTER CONSIDERATION OF 12 UTC
MODELS AND ENSEMBLES THAT SHOW REASONABLE SUPPORT...EXCLUDING THE
DISCOUNTED/OUTLIER PROGRESSIVE GFS.
THIS BLENDED SOLUTION ALSO PROVIDES MORE OF A COMPROMISE
DOWNSTREAM MID-UPPER LEVEL TROUGH AMPLITUDE OVER ERN CANADA AND
DOWN ACROSS THE ERN US INTO DAYS 6/7 BETWEEN THE MORE AMPLIFIED
GFS/GFS MEAN/CANADIAN/NAEFS AND THE LESS DEFINED ECMWF/ECMWF
ENSEMBLE MEANS. SUSPECT THIS TROFFING MAY HAVE DECENT SENSIBLE
WEATHER FOCUSING NRN AND SEPARATE SRN STREAM STRUCTURE FOR
MID-SUMMER CONSIDERING UPSTREAM RIDGE POTENTIAL...SO THE 50-50
BLEND WAS THEN MANUALLY ADJUSTED TO AT LEAST SLIGHTLY BETTER SHOW
THIS POTENTIAL.
ROTH/SCHICHTEL
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