522
FXUS02 KWBC 071741
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
141 PM EDT THU AUG 07 2008
VALID 12Z SUN AUG 10 2008 - 12Z THU AUG 14 2008
FORECAST CONFIDENCE ACROSS THE NATION DURING THE MEDIUM RANGE
PERIOD IS BELOW AVERAGE AS PER HIGH SPREAD AMONG THE
MODELS/ENSEMBLES AND RELATIVELY POOR RUN-RUN CONTINUITY. IMPULSE
ENERGY INTERACTIONS WITH A CENTRAL NOAM RIDGE AS WELL AS
DOWNSTREAM BLOCKING SEEM TO PRIMARILY ACCOUNT FOR THE SENSITIVE
NATURE OF GUIDANCE WITHIN THE TOTAL RANGE OF SOLUTIONS BUT OVERALL
THE 00 UTC CANADIAN SEEMS TO OFFER A SOLUTION THAT BEST FITS THE
OVERALL FLOW.
A DAVIS STRAIT BLOCK APPEARS TO BE ONE SOURCE OF THE MIXED
MESSAGES...THE INTENSITY...AREAL EXTENT...AND LIFESPAN OF WHICH
HAVE A DIRECT BEARING ON THE FLOW OVER THE EASTERN HALF OF THE
CONTINENT. EVEN ALONG THE WEST COAST...THE DOWNSTREAM ROADBLOCK
SEEMS TO AT LEAST PARTLY AFFECT THE LATITUDE AND PROPORTION OF THE
SPLIT FLOW THERE. THE 00Z GFS IS A MARKED OUTLIER WITH THE ROBUST
VORTEX IT DEPICTS EARLY DAY 3 OVER THE LOWER SAINT LAWRENCE
VALLEY...WITH THE 00Z ECMWF ON ITS OWN DIGGING A SHARP SHORTWAVE
INTO PENNSYLVANIA AND NEW YORK STATE DAY 4...WITH MODEL
DIFFERENCES STARTING WELL INTO THE SHORT RANGE. WATER VAPOR
IMAGERY SHOWS A STRONGLY BUILDING RIDGE OVER WRN CANADA AHEAD OF
AN UNSEASONABLY AMPLIFIED NE PAC CLOSED LOW. THIS SUGGESTS THAT
THE DOWNSTREAM DIGGING OF CENTRAL CANADA ENERGY TO THE LEE OF THE
RIDGE MAY BE QUITE SHARP...LIKELY MORE IN LINE WITH A SOLUTION AS
STRONG AS THE 00 UTC CANADIAN THAT ALONG WITH THE 00 UTC ECMWF
ENSEMBLES ARE NOT QUITE AS STRONG THE 00 UTC ECMWF. THE 12 UTC
GFS HAS CERTAINLY TRENDED SIGNIFICANTLY TOWARD THIS TYPE OF
SOLUTION DAYS 1-4/5...BUT PROBABLY RETROGRADES ENERGY TOO MUCH
UNER THE RIDGE DAYS 6/7 CONSIDERING MODEL BIAS. THE 12 UTC
CANADIAN HAS MAINTAINED CLOSE AGREEMENT WITH THE 00 UTC CANADIAN
BOLSTERING MY CONFIDENCE. THE 00/12 UTC CANADIAN RUNS ALSO IN
PARTICULAR ALLOW SUBSEQUENT UPSTREAM NRN STREAM KICKER ENERGY
WITHIN ESTABLISHED DIGGY FLOW LEE OF THE RIDGE KEEP AMPLIFIED LEAD
TROF ENERGY AT LEAST SLIGHTLY MORE PROGRESSIVE THAN THE 00 UTC
ECMWF.
UPSTREAM...THE CENTRAL CANADIAN RIDGE IN THE 00 UTC CANADIAN ALSO
ACTS TO BLOCK FLOW MORE EFFECTIVELY THAN A CONSENSUS OF ALL
GUIDANCE INTO THE LATER PART OF THE FORECAST. A SOLUTION MORE IN
THAT VEIN OR EVEN AS PER A COMPOSITE OF RECENT GFS/GEFS RUNS SEEMS
MORE REASONABLE THAN THE 00 UTC ECMWF THAT BLASTS PAC ENERGY
ROBUSTLY THRU W-CENTRAL CAN TUE-THU.
OVERALL AND THE BEST NOD TO CONTINUITY SEEMS TODAY TO USE AS A
TEMPLATE FOR HPC GUIDANCE PROGS THE UNUSUAL PAIRING OF THE 00 UTC
CANADIAN BLENDED/SMOOTHED WITH ABOUT 20-30% FROM A REASONABLY
SUPPORTIVE 00 UTC ECMWF ENSEMBLE MEAN DAYS 3-7.
CISCO/SCHICHTEL
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