667
FXUS02 KWBC 061841
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
240 PM EDT SUN SEP 06 2009
VALID 12Z WED SEP 09 2009 - 12Z SUN SEP 13 2009
TELECONNECTIONS WITH A POTENT NEGATIVE HEIGHT ANOMALY NEAR 48N
143W THAT HAS AMPLE MODEL AND ENSEMBLE SUPPORT FAVORS DOWNSTREAM
RIDGING ACROSS THE PACIFIC NORTHWEST AND TROUGHING ACROSS THE
EAST-CENTRAL US. THE MODELS GENERALLY SHARE THESE IDEAS...BUT
DIFFER CONCERNING THE EVOLVING AMPLIFICATION OF THE FLOW PATTERN
BOTH ACROSS THE EASTERN PACIFIC INLAND ACROSS THE WRN THROUGH
EAST-CENTRAL US...WITH THE 00Z CANADIAN BRINGING A SYSTEM EASTWARD
ACROSS CANADA LATE IN THE PERIOD WHILE THE 00Z GFS/ECMWF/UKMET DIG
THE SYSTEM SHARPLY SEWD INTO THE US. GFS/CANADIAN/NAEFS ENSEMBLES
AND ESPECIALLY ECMWF ENSEMBLE MEMBERS SHOW A SIGNIFICANT NUMBER OF
CLOSED SOLUTIONS INTO LATE WEEK ACROSS THE MIDWEST/GREAT
LAKES...TOO MANY TO IGNORE. AM LEARY TO AMPLIFY THE FLOW QUITE AS
MUCH AS THE 00 UTC ECMWF BY NEXT WEEKEND THOUGH CONSIDERING
CONTINUITY FROM YESTERDAYS MUCH FLATTER 12 UTC ECMWF RUN.
HOWEVER...THAT 12 UTC ECMWF RUN MAY BE AN OUTLIER AS IT DOES SEEM
TO FIT WELL WITH THE AMPLIFYING UPSTREAM LONGWAVE PATTERN SHOWN IN
MOST GUIDANCE NOR WITH ITS MORE AMPLIFIED 12 UTC ECMWF ENSEMBLES
FROM YESTERDAY AND LATEST 00 UTC ECMWF ENSEMBLES. ALL SAID... HPC
PROGS WERE PRIMARILY DERIVED FROM A BLEND THE 00 UTC ECMWF AND NOT
QUITE AS AMPLIFIED ECMWF ENSEMBLE MEAN. THIS SOLUION WOULD STILL
BRING QUITE AN EVOLVING OCCLUDED CYCLONE AND ASSOCIATED TRAILING
FRONTAL SYSTEM AND SENSIBLE WEATHER FOCUS SOUTHEAST OUT OF CENTRAL
CANADA ACROSS THE CENTRAL AND EAST-CENTRAL US DAYS 4-7. WE SEE NO
COMPELLING REASON TO ADJUST CONTINUITY FOR OUR FINAL PROGS AFTER
SEEING OVERALL FAVORABLE SUPPORT/TRENDS FROM A COMPOSITE OF 12 UTC
GUIDANCE.
FOR THE LOW OFF THE EAST COAST ALONG THE LONG-LIVED STATIONARY
FRONT...MULTI-MODEL ENSEMBLE CLUSTERINGS BRING/KEEP SURFACE LOW
FOCUS JUST OFFSHORE THE MID-ATLANTIC AND NORTHEAST STATES. THIS
IDEA GENERALLY FOLLOWED HPC PROGS IS SLOWER THAN MOST GLOBAL MODEL
GUIDANCE BUT MAY BE MORE REASONABLE CONSIDERING BLOCKING HIGH
PRESSURE TO ITS NORTH MAY PROVE SLOW TO ERODE. THIS SOLUTION IS
CLOSEST TO THE 00 UTC ECMWF/UKMET DETERMINISTIC MODELS. IN
CONTRAST BUT STILL PLAUSIBLE...THE 00 UTC CANADIAN OFFERS A
TRACK/HEAVIER PCPN FOCUS FARTHEST INLAND AND THE 00/06 UTC GFS IS
MORE PROGRESSIVE RUNNING NNEWD OFFSHORE. ALL OFFER POTENTIAL FOR
LEAD AND SUBSEQUENT FRONTAL WAVE DEVELOPMENT AND THE CONVECTIVE
NATURE ALONG THE WAVY BOUNDARY AS PER LATEST SATL LOOPS SUPPORTS
ORGANIZED COASTAL LOW PCPN POTENTIAL. HOWEVER...CONFIDENCE IS
VERY LOW WITH SMALLER SCALE DETAILS AND CONVECTIVE INTERACTIONS
STEMMING FROM VARIED SHORT TO MEDIUM RANGE 12 UTC MODEL GUIDANCE.
ROTH/SCHICHTEL
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