092
FXUS02 KWBC 101805
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
203 PM EDT SAT OCT 10 2009
VALID 12Z TUE OCT 13 2009 - 12Z SAT OCT 17 2009
...STRONG EAST PACIFIC STORM TO AFFECT NORTHERN AND CENTRAL
CALIFORNIA EARLY THIS WEEK...
GUIDANCE REMAINS FAIRLY WELL ON TRACK REGARDING THE FCST SCENARIO
OF A COMBINATION OF INITIAL ERN PAC TROF ENERGY AND SOME NRN
STREAM ENERGY EVENTUALLY AMPLIFYING OVER THE ERN CONUS BY LATE
NEXT WEEK WHILE AN ERN PAC TROF AND WEST COAST OR WRN NOAM RIDGE
EVOLVES UPSTREAM. LATEST GEFS/ECMWF/CANADIAN ENSEMBLE MEANS
CONTINUE TO SHOW UNUSUALLY GOOD AGREEMENT WITH THE LARGE SCALE
EVOLUTION AND THEREFORE ARE PREFERRED FOR THE MID-LATE PORTION OF
THE FCST WHILE AWAITING BETTER OPERATIONAL MODEL
CONTINUITY/AGREEMENT REGARDING THE FINER DETAILS. BY THE LATTER
PART OF THE PERIOD THE 00Z GFS AND ECMWF RUNS BOTH OFFER SOME
QUESTION MARKS WHEN COMPARED TO THE DOMINANT ENSEMBLE CONSENSUS...
WITH THE GFS POSSIBLY BECOMING TOO PROGRESSIVE FROM THE ERN PAC
INTO WRN-CNTRL NOAM AND TOO AGGRESSIVE WITH THE SEWD EXTENT OF ERN
CONUS TROF ENERGY. MEANWHILE THE ECMWF RIDGE OVER THE ERN PAC BY
DAY 7 SAT IS ALIGNED FARTHER WWD THAN CONSENSUS OR AVERAGE OF
PREVIOUS RECENT ECMWF RUNS. EARLY IN THE PERIOD... THE GFS/GEFS
MEAN IS IN THE SRN PORTION OF THE SOLN SPREAD WITH DEEP LOW
PRESSURE OVER THE ERN PAC WITH SOME MID LVL HGT ANOMALIES REACHING
4-6 STANDARD DEVIATIONS BELOW NORMAL. MEANWHILE THE GFS IS ONE OF
THE STRONGEST SOLNS WITH LOW PRESSURE CROSSING NEW ENGLAND ON
TUE... BUT THE ECMWF IS ON THE WEAK EDGE OF GUIDANCE WITH THIS
SYSTEM. DAYS 3-4 TUE-WED START WITH A BLEND OF THE
ECMWF/CANADIAN/GFS IN DECREASING ORDER OF WEIGHTING TO ACCOUNT FOR
THE ARRAY OF LATEST GUIDANCE WITH THE AFOREMENTIONED SYSTEMS AND
TO YIELD A MODEST WAVE OVER THE SOUTHEAST AS OF EARLY DAY 4 WED.
THEN DAYS 5-7 THU-SAT EMPLOY AN EVEN BLEND OF THE 00Z GEFS/12Z
ECMWF ENSEMBLE MEANS TO REPRESENT THE CONSENSUS ENSEMBLE MEAN
HANDLING OF FLOW ALOFT AND THE CORRESPONDING SFC EVOLUTION.
UPDATED MORNING PRELIMS REMAIN SIMILAR WITH AN EQUAL BLEND OF 00Z
GFS/ECMWF THRU DAYS 5 THEN ADDING IN THE ENS MEANS OF GFS AND
ECMWF TO THE 00Z OP GFS FOR DETAIL DAYS 6 AND 7.
12Z GUIDANCE REMAINS SIMILAR ENOUGH TO KEEP PRIOR PROGS AS A BASE
FOR AFTN FINALS
STRONG EPAC STORM DAYS 3 AND 4 WITH A HIGH IMPACT ON THE CENTRAL
NRN CA COAST AND NWD ALONG THE PAC NW COAST WILL BE THE MAIN
WEATHER STORY THIS PERIOD. HIGH ONSHORE WINDS WITH A LONG FETCH
WILL AFFECT THE COASTAL AREAS WITH VERY HVY RAINFALL FROM THE
CENTRAL CA COAST AND NWD AND EWD INTO THE SIERRA. POTENTIAL FOR
HVY COASTAL RAINS SOUTH OF PT CONCEPTION. INGREDIENTS COMING INTO
PLACE WITH VERY LOW ANOMALOUS MID LEVEL HTS OFF THE COAST COMBINED
WITH HIGHLY ANOMALOUS PWS/850-700 MB MOISTURE FLUX/ AND INCREASED
DIVERGENCE UNDER THE RIGHT FRONT EXIT REGION OF THE JET CORE
COMING INTO THE CA COAST AND AIDED BY OROGRAPHIC EFFECTS WITH HIGH
LOW LEVEL WINDS SETTING THE STAGE FOR HVY TO EXCESSIVE RAINFALL
TUES INTO WED. EXPECT WIDESPREAD 4-6 INCH RAINFALL AMOUNTS TO BE
COMMON AND HIGHER OVER FAVORABLE TERRAIN IN LESS THAN 24 HRS. HIGH
CONFIDENCE FORECAST. SYNOPTIC SIMILARITIES TO COLUMBUS DAY 1962
STORM. SEE LOCAL NWS FORECASTS AND ADVISORIES.
ELSW THE SERN PLAINS EWD THRU THE TN VALLEY TO THE SOUTHEAST COAST
WILL BE UNDER THE RIGHT REAR ENTRANCE REGION OF AN UPPER LEVEL JET
ENHANCING UPPER LEVEL DIVERGENCE AND AIDING IN MDT TO HVY RAINS
FROM THE LOWER RED RIVER VALLEY INTO AR/NRN LA AND ACROSS N
PORTIONS OF MS/AL/GA AND INTO SC DAYS 3-5 TUES-THURS. AMPLIFYING
MID LEVEL TROF THU INTO SAT CENTRAL AND ERN CONUS WILL HAVE SFC
WAVE DEVELOPMENT FROM THE LOWER MS VALLEY MOVING NEWD OFF THE
SOUTHEAST OR MID ATLC COAST LATE FRI-SAT. LOCATION AND TRACK OF
THIS SYSTEM MORE UNCERTAIN AT THIS TIME AS UKMET CONTS ITS WEST OF
APPLCHNS TRACK AND ENS MEANS OF GFS AND ECMWF SUGGEST POTENTIAL OF
REFORMING COASTAL LOW BEING NORTH OF OP MODEL DEPICTION.
WIDESPREAD MDT RAIN IMPACT FROM THE GULF COASTAL STATES EAST AND
NORTHEAST AS FAR AS NEW ENG.
WET CONDITIONS WILL PERSIST OVER THE PAC NORTHWEST THU INTO SAT
WITH ONSHORE MID LEVEL FLOW. OP MODELS MORE UNCERTAIN HERE AND A
PREFERENCE TOWARDS THE AGREED UPON ECMWF/GFS ENS MEANS OF A RIDGE
AXIS ALONG 120W.
RAUSCH/ROSENSTEIN
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