050
FXUS02 KWBC 071807
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
207 PM EDT FRI AUG 07 2009
VALID 12Z MON AUG 10 2009 - 12Z FRI AUG 14 2009
A PROGRESSIVE FLAT FLOW PATTERN IS EXPECTED ACROSS THE NORTHERN
TIER OF THE COUNTRY THIS PERIOD...WHICH IS SHOWN BY ALL THE
AVAILABLE GUIDANCE WITH THE WESTERLIES FINALLY MOVING TO
CLIMATOLOGICALLY NORMAL SRN CANADA OTHER THAN ACROSS THE NORTHERN
PLAINS/SOUTHEAST CANADA EARLY ON...THE 00Z ECMWF BECOMES AN
OUTLIER AS SOON AS TUESDAY ACROSS ALASKA...BUT IT DOES NOT FALL
OUT OF LINE WITH THE ENSEMBLE MEANS ACROSS THE LOWER 48 UNTIL LATE
WEDNESDAY. FOLLOWING FROM SHORT RANGE...WHERE A SOLUTION SIMILAR
TO A 00Z ECMWF/00Z GFS COMPROMISE WAS PREFERRED...USED THIS BLEND
FOR EARLY PRELIMS UNTIL LATE WEDNESDAY WHEN THE 00Z GEFS MEAN WAS
USED INSTEAD OF THE ECMWF. EVEN FOLLOWING THIS
COMPROMISE...ADJUSTMENTS NEEDED TO BE MADE PER THE 12Z MULTI-MODEL
ENSEMBLE LOW CLUSTERING. AFTER THOSE ADJUSTMENTS WERE MADE...THE
FORECAST KEPT REASONABLE CONTINUITY.
UPDATED MORNING PRELIMS SIMPLIFY THE SOLUTION TOWARDS USING A
50/50 ECMWF AND ECMWF ENS MEAN THRU DAY 5 THEN A MAJORITY OF ECMWF
ENS MEANS DAYS 6 AND 7. ECMF AND GSF ENS MEANS ARE SIMILAR THRU
THE PERIOD AND LESSEN AN ABERRANT LOCATIONAL PROBLEMS OF
INDIVIDUAL OP MODELS.
12Z GFS SIMILAR TO PRIOR RUNS AND WITHIN ENVELOPE OF SOLUTIONS BUT
NOT SUPERIOR TO PRIORLY USED ENS MEANS WITH ANY DEGREE OF
CONFIDENCE. SAME WITH CMC AND UKMET. NO CHNAGES TO PRIOR PROGS FOR
AFTN FINALS.
ROTH/ROSENSTEIN
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