778
FXUS10 KWNH 091848
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
147 PM EST MON NOV 09 2009
VALID NOV 09/1200 UTC THRU NOV 13/0000 UTC
...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING THE NEW ECMWF AND FINAL PREFERENCES
INITIALIZATION ERRORS WITH THE NAM/GFS DO NOT APPEAR TO
SIGNIFICANTLY IMPACTS THEIR FORECASTS.
..COLD FRONT NEAR THE PACIFIC NORTHWEST COAST
THE MODELS...INCLUDING THE NAM AND GFS...SHOW GOOD AGREEMENT ALOFT
AND AT THE SURFACE WITH THE PASSAGE AND STRENGTH OF THIS FRONTAL
SYSTEM THROUGH THE REGION.
...SEVERAL SHORTWAVE TROUGHS AMPLIFYING AND REACHING THE WEST DAYS
2/3...
PREFERENCE: SEE BELOW EACH PARAGRAPH
THE MODELS ARE MOSTLY SIMILAR WITH THE ARRIVAL AND INFLUENCE OF A
LEAD SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST TUE
NGT/WED...BEFORE THE NAM DRIFTS TOWARD THE SLOW EDGE OF THE
GUIDANCE WITH ITS SURFACE LOW EVOLUTION NEAR THE NORTH
DAKOTA/SASKATCHEWAN BORDER BY 84 HRS...WITH STRONG CONSENSUS THAT
THE TROUGH WILL HAVE ENTERED CANADA FASTER THAN THE NAM.
PREFERENCE: AFTER 00Z THU...1/2 EACH GFS/ECMWF
MEANWHILE...THE MODELS SHOW SIMILAR TIMING WITH THE ARRIVAL AND
PASSAGE OF A SUBSEQUENT SHORTWAVE TROUGH REACHING WASHINGTON WED
NGT...WITH THE THE ECMWF STRONGEST...FOLLOWED BY THE GFS THEN THE
NAM. THE NEW CANADIAN/UKMET AND MULTI-MODEL ENSEMBLES ARE A LITTLE
STRONGER THAN THE NAM...THUS SUPPORTING A SOLUTION CLOSEST TO THE
GFS.
PREFERENCE: GFS
FARTHER SOUTH AND MOSTLY INTO DAY 3...THE NAM IS NEARLY A
STRONG/SLOW OUTLIER WITH A MORE SOUTHERN STREAM SHORTWAVE TROUGH
REACHING CENTRAL CALIFORNIA BEFORE ACCELERATING INLAND.
OTHERWISE...THE GFS/ECMWF SHOW SIMILAR INTENSITY...WITH THE ECMWF
SLIGHTLY FASTER. DETERMINISTIC SPREAD AND ENSEMBLE SPAGHETTI
DIAGRAMS FULLY SUPPORT THE DIFFERING SPEEDS WITH A BLEND OF BOTH
SOLUTIONS RECOMMENDED.
PREFERENCE: 1/2 EACH GFS/ECMWF
..HURRICANE IDA
..INTERACTION OF IDA WITH SHORTWAVE TROUGH OVER TEXAS
THE MAJORITY OF MODELS...INCLUDING THE NAM...ALLOW THE APPROACHING
SHORTWAVE TROUGH TO PULL IDA IN A NORTHWESTERLY DIRECTION UNTIL
THEY CONSOLIDATE NEAR THE GULF COAST BY 12Z TUE. HOWEVER...
THE NAM LIES NEAR THE SOUTHWEST OR SLOW EDGE OF THE GUIDANCE
DURING THIS PROCESS AND IS CONSIDERED LEAST RELIABLE...WHILE ALL
OTHER GUIDANCE...INCLUDING THE GFS/ECMWF ALLOW THE CONSOLIDATED
LOW TO DRIFT EASTWARD INTO THE FLORIDA PANHANDLE BY TUE...WHICH IS
IN GOOD AGREEMENT WITH HURRICANE MODEL GUIDANCE. REFER TO THE TPC
FOR THE OFFICIAL FORECAST.
..SHORTWAVE TROUGH AMPLIFYING OVER THE EAST TUE/WED
PREFERENCE: 1/2 GEFS MEAN TO 1/4 EACH GFS/CANADIAN
THERE HAS BEEN A NOTABLE TREND IN THE MAJORITY OF GUIDANCE THE
LAST TWO DAYS TO DELAY A COMPLICATED PHASING PROCESS OF THIS
TROUGH WITH A SEPARATE SHORTWAVE TROUGH MOVING INTO THE SOUTHEAST
UNTIL BOTH TROUGHS REACH THE EAST COAST. THE NAM AND MULTI-MODEL
ENSEMBLE MEANS WERE FIRST TO DISPLAY A LESS-PHASED OR UNPHASED
SOLUTION 1-2 DAYS AGO...WITH THE DETERMINISTIC GUIDANCE SLOWLY
COMING INTO AGREEMENT. THE NEW NAM CONTINUES TO SHOW NO
PHASING...BUT IS MOSTLY DUE TO ITS SLOW OUTLIER SOLUTION IN THE
GULF...SO THE NAM CAN NOT PHASE. MEANWHILE THE NEW GFS HAS TRENDED
TOWARD SLOWER AND WEAKER PHASING...RESULTING IN A LESS PRONOUNCED
SURFACE LOW OFF THE GA/SC COAST...WITH REASONABLY GOOD SUPPORT
PROVIDED FROM THE CANADIAN AND GEFS MEAN...
ALBEIT WEAKER AND MORE SUPPRESSED THAN THE GFS. THE ECMWF/UKMET
NOW REMAIN THE ONLY DETERMINISTIC SOLUTIONS SUPPORTING
CONSIDERABLE SURFACE LOW DEVELOPMENT OFF THE SC COAST BY THU.
THUS...WILL MAINTAIN CONTINUITY WITH PRIOR REASONING THAT THE
POSITIVELY-TILTED LONGWAVE PATTERN AND ITS SUBSEQUENT SHORTWAVE
PATTERN SUPPORT A SUPPRESSED AND PROGRESSIVE SURFACE LOW
EVOLUTION...WHICH IS CLOSEST TO THE GEFS MEAN.
...MODEL TREND GRAPHICS AT
WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...
...500 MB FORECASTS AT
WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...
JAMES
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