181
FXUS02 KWBC 031931
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
330 PM EDT THU SEP 03 2009
VALID 12Z SUN SEP 06 2009 - 12Z THU SEP 10 2009
EARLY PRELIM...USED THE 00Z/02 ECMWF FOR THE PRELIMINARY FRONTS
AND PRESSURES FOR DAYS 3 AND 4...WITH A PROGRESSIVE BLEND TOWARD
THE 00Z/01 EC ENSEMBLE MEAN THEREAFTER. THE CURRENT DETERMINISTIC
ECMWF IS IN BETTER HARMONY WITH THE EC MEAN FROM 24 HOURS AGO THAN
THE MEAN FROM THE 12Z/01 RUN...SOLUTIONS WHICH...LIKE THE 00Z/02
GFS AND UKMET...DO NOT ALLOW MUCH COLD AIR TO DIG INTO
SOUTHEASTERN CANADA DURING THE SECOND HALF OF THE FORECAST PERIOD.
THE FUTURE OF ERIKA IN THE ATLANTIC IS QUITE UNCERTAIN...SO WILL
DEFER TO A COLLABORATION WITH TPC LATER TODAY ON THE TRACK OF THE
SYSTEM BY DAYS 6 AND 7. THE HEAVY RELIANCE ON THE EC MEAN SHOULD
HELP TO MITIGATE THE AMPLITUDE DIFFERENCES SEEN AMONG THE MODELS
WITH THE LONGWAVE TROUGH PROGRESSING ACROSS THE WESTERN HALF OF
NORTH AMERICA AFTER DAY 5.
UPDATED PRELIM...OP MODELS AND ENSMEBLES ARE IN GOOD AGREEMENT
DAYS 3-5 AND A BLEND OF OP RUNS OF 00Z ECMWF AND GFS WILL SUFFICE.
UPSTREAM PAC DIFFERENCES RESULT IN A VAST DIFFERENCE AND WIDE
SPREAD OF SOLUTIONS ESPECIALLY OVER WRN CONUS AS GFS KEEPS MORE
ZONAL FLOW INTO THE WEST WHILE THE ECMWF CARVES OUT A DEEP TROF
WITH THE OP SOLUTION AT THE BASE OF THE ENSEMBLE SPREAD.
TELECONNECTIONS ON A POSITIVE HT ANOMALY OVER JAMES BAY SUPPORTS
AT LEAST SOME WRN TROF AND A BLEND OF GFS/ECMWF ENS MEANS
PREFERRED HERE FOR DAYS 6 AND 7 TUES/WED.
MOST OP MODELS AND MEANS SUPPORT WHAT IS LEFT OF ERIKA BEING OFF
THE SRN SEABOARD DAY 7 WED
AND AFTN FINAL PROGS REFLECT A TROF AT THIS TIME WITH TPC CO
ORDINATION. LARGE AMONT OF UNCERTAINTY REMAINS WITH TRACK AND
INTENSITY GUIDANCE. COORDINATED TROPICAL WAVE POSITION BY DAY 7
MAY BRING SHOWERS INTO THE BAHAMAS/FL AND THE SOUTHEASTERN
SEABOARD ALONG THE PERSISTENT COASTAL FRONTAL BOUNDARY DEPENDING
UPON WHAT IS LEFT OF THIS SYSTEM. SEE TPC DISCUSSIONS.
MONSOONAL MOISTURE WILL INCREASE OVER THE SOUTHWEST/FOUR CORNERS
AREA EARLY IN THE PERIOD AND CONTINUE INTO AT LEAST MID WEEK.
COLD FRONT AND MID LEVEL TROF WILL BRING IN SHOWERS ACROSS THE
PACIFIC NORTHWEST SAT INTO MON.
THE CENTRAL U.S. WILL BE WET THIS PERIOD WITH A LARGE MID LEVEL
LOW TRIGGERING SHOWERS IN THE CENTRAL TO LOWER MS VALLEY AND WWD
TO TX REGION EARLY ON THEN SHIFTING EAST AND NEWD INTO THE LOWER
OH VALLY AND NWD INTO THE GREAT LAKES REGION.
CISCO/ROSENSTEIN
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