591
FXUS02 KWBC 091815
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
214 PM EDT WED SEP 09 2009
VALID 12Z SAT SEP 12 2009 - 12Z WED SEP 16 2009
TELECONNECTIONS WITH A POSITIVE ANOMALY ACROSS NORTHERN
ONTARIO/HUDSON BAY FAVORS A PROGRESSIVE DEEP CYCLONE TO ITS SOUTH.
AN AMPLIFIED TROUGH OF THE WEST COAST FAVORS RIDGING IN THE WEST
THROUGH THE FORESEEABLE FUTURE. THE MODELS GENERALLY FAVOR THESE
IDEAS...THOUGH THE 00Z ECMWF/00Z GFS DEPART FROM THE GUIDANCE IN
THEIR RETROGRESSION OF THE DEEP CYCLONE IN THE NORTHERN
PLAINS/UPPER MIDWEST TOWARDS MONTANA DUE TO GREATER RIDGING TO ITS
NORTH. THE ENSEMBLE GUIDANCE REMAINS STATIC...STILL FAVORING THE
SYSTEM TO LURK FARTHER TO THE EAST CLOSEST TO THE 00Z CANADIAN
SOLUTION. STARTED WITH A 00Z CANADIAN/00Z GEFS MEAN COMPROMISE TO
STAY IN THE MIDDLE OF THE ENSEMBLE SPREAD...AND MADE ADJUSTMENTS
TO SURFACE LOW POSITIONS BASED UPON THE 12Z MULTI-MODEL ENSEMBLE
LOW CLUSTERING...SUCH AS ALONG THE EAST COAST AND WITH THE LOW
MOVING OUT OF THE WESTERN GULF OF MEXICO UP AN APPROACHING FRONTAL
BOUNDARY. THIS SOLUTION MAINTAINED REASONABLE CONTINUITY.
MORNING UPDATED PRELIMS DIFFER SLIGHTLY WITH AN INCORPORATION OF
OP CMC WHICH HOLDS ON TO A MID NATION/ CENTRAL TO NRN PLAINS
CUTOFF LOW MUCH LONGER THAN OP 00Z RUNS ECMWF AND GFS. 00Z UKMET
SIMILAR TO THE CMC AS IS THE 12Z ECMWF ENS MEAN AND 00Z GFS ENS
MEAN. LOW CONFIDENCE IS USUALLY THE RULE WITH AN ANY CUTOFF LOW
AND CHANGE OF CONTINUITY OF THE OP RUNS OF GFS/ECMWF CERTAINLY
DOES NOT ADD CONFIDENCE IN SPITE OF THEIR BEING IN LOCK STEP. IN
ADDITION THE LAGGED AVERAGE FORECASTS OF BOTH GFS AND ECMWF
INDICATE KEEPING THE MID LEVEL LOW/CUTOFF LOW IN THE CENTRAL/NRN
PLAINS.
PREFER A BLEND OF 00Z OP CMC/ 12Z ECMWF ENS MEAN AND 00Z GFS ENS
MEAN. NOT ADDED BECAUSE THE RUN STOPS AT 144 HRS BUT CONSIDERED IS
THE 00Z UKMET SOLUTION WHICH IS ALSO A BETTER MATCH TO THE ENS
MEANS WITH THE PAC TROF THAN THE OP ECMWF.
12Z MODEL RUNS HAVE HELPED RESOLVE SOME OF THE UNCERTAINTY AS OP
MODELS 12Z UKMET AND CMC HAVE GONE TOWARDS THE GFS/ECMWF SOLUTION
OF ROTATING THE CENTRAL AND NRN PLAINS CUTOFF LOW CLOCKWISE AND
LIFTING IT OUT NWD INTO CANADA. 12Z GFS LAGS BEHIND KEEPING A MEAN
SOLUTION OF THE CUTOFF LOW WELL EASTWARD BUT THIS MAY NE MORE OF A
RESOLUTION PROBLEM. HAVE MADE MAJOR ADJUSTMENTS TOWARDS THE 12Z
GFS AND SOME RESIDUAL PRIOR HPC PROG ON A 70/30 BASIS. MAJOR MID
NATION POPS/TEMPS ADJUSTMENTS MADE.
ROTH/ROSENSTEIN
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