699
FXUS02 KWBC 131751
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
151 PM EDT THU AUG 13 2009
VALID 12Z SUN AUG 16 2009 - 12Z THU AUG 20 2009
OVERNIGHT PRELIMS USED A BLEND OF THE 00Z GFS/00Z GEFS MEAN AND
12Z ECMWF/12Z ECMWF ENSEMBLE MEAN SOLUTIONS. THE CONSENSUS
APPROACH WAS USED TO DAMPEN OUT INDIVIDUAL UNCERTAIN MODEL
DETAILS. THUS HAVE BLENDED 00Z OPERATIONAL GFS AND 12Z ECMWF AND
TO INCORPORATE THE WELL CLUSTERED 00Z GFS MEAN/ 12Z ECMWF ENS
MEAN/00Z CANADIAN GLOBAL ENSEMBLE MEAN SOLUTIONS. THE MODELS
INDICATE A CLOSED LOW SFC AND ALOFT APPROACHING THE UPPER
ALEUTIANS OF AK/ADJACENT GULF OF AK. THIS TELECONNECTS WITH MID
LEVEL RIDGING MOVING INLAND FROM THE PACIFIC NORTHWEST TO THE
NORTHERN ROCKIES AND MID LEVEL TROUGH MOVING FROM THE PLAINS
TOWARDS THE UPPER LAKES. THIS IS SHOWN IN MOST INDIVIDUAL MODEL
SOLUTIONS...WITH THE 00Z CANADIAN GLOBAL AND 00Z ECMWF FINDING A
SHORTWV DIGGING DOWN THE BACK SIDE OF THE TROUGH OVER THE UPPER
LAKES AND PRODUCING A SEPARATE SFC LOW FURTHER WEST-SOUTHWEST OVER
THE NORTHERN PLAINS VS THAT SHOWN IN THE 00Z GFS/12Z ECMWF AND
RESPECTIVE 00Z NCEP/12Z ECMWF/00Z CANADIAN ENSEMBLE MEANS. BETTER
CLUSTERING AMONG THE LATTER SOLUTIONS AND BETTER AGREEMENT WITH
THE TELECONNECTIONS LEAD TO THE PREFERENCE TO BLEND THE CLUSTERED
MODEL/ENSEMBLE MEAN SOLUTIONS.
UPDATED MORNING PRELIMS USE THE 00Z ECMWF ENS MEAN WITH THIS BLEND
AND IS SUPPORTED BY THE 00Z LAGGED AVERAGE BLENS AND 06Z OP GFS.
ALL MODELS AND ESP MEANS OF GFS/ECMWF INDICATE A ROCKIES RIDGE AND
DOWNSTREAM TROF ALONG 90W-85W LATE PERIOD INTO LATE NEXT WEEK AND
WEEKEND. ORIENTATION OF THIS PATTERN WILL BECOME CRUCIAL IMPACTING
THE TRACK OF THE ATLANTIC TROPICAL SYSTEMS.
AVAILABLE 12Z MODEL RUNS OFFER LITTLE CHANGES AND A PRIOR PREFERED
SOLUTION REMAINS FOR HPC PROGS.
ATLANTIC TROPICS ARE FORECAST TO BE QUITE ACTIVE THIS
PERIOD...WITH MODELS TRACKING A COUPLE OF SYSTEMS MOVING WEST
ACROSS THE ATLANTIC. AT THIS TIEM TE SECOND OF THESE SYSTEM MAY
AFFECT THE LESS ANTILLES BY DAY 7 THURSDAY. SEE NHC
DISCUSSIONS/ADVISORIES FOR THESE SYSTEMS. ROUTINE TPC/HPC
COORDINATION HAS DETERMINED POSITIONS IN CHARTS THRU DAY 7.
PETERSEN/ROSENSTEIN
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