259
FXUS10 KWNH 140444
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 AM EDT SAT MAR 14 2020
VALID MAR 14/0000 UTC THRU MAR 17/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z PRELIMINARY MODEL EVALUATION WITH FINAL PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW DROPPING ALONG THE WEST COAST THROUGH TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE EVOLUTION OF A
CLOSE LOW MOVING SOUTHWARD FROM JUST OFF THE WASHINGTON STATE
COAST TO WEST OF THE CENTRAL CALIFORNIA COAST TUESDAY MORNING.
THERE IS LITTLE DISCREPANCY IN THE POSITION OR INTENSITY OF THIS
MID-LEVEL FEATURE IN ANY OF THE AVAILABLE GUIDANCE. ALTHOUGH THE
PRIMARY SYNOPTIC EVOLUTION IS WELL AGREED UPON, THERE DOES EXIST
DISCREPANCY IN TIMING AND INTENSITY OF SMALLER-SCALE SHORTWAVE
ROTATING AROUND THE PARENT LOW AND EJECTING ONSHORE THE WEST
COAST. THESE ARE TOO SMALL TO BE MODELED WELL BEYOND NEAR TERM
TIME RANGES, AND SINCE THE GENERAL EVOLUTION IS WELL MODELED, A
GENERAL BLEND IS ACCEPTABLE.
...WEAKENING MID-LEVEL SHORTWAVE MOVING FROM THE SOUTHWEST TO THE
MID-ATLANTIC INTO SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM/GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 00Z GFS IS BY FAR A FAST OUTLIER WITH THE EJECTION OF THIS
WEAKENING WAVE, BECOMING WELL AHEAD OF THE CONSENSUS AND OTHER
MODELS AS EARLY AS 12 HOURS INTO THE FORECAST PERIOD. RECENTLY THE
GFS HAS BEEN VERIFYING TOO FAST, SO EXPECT THIS EVOLUTION IS ALSO
TOO QUICK AND THE GFS IS REMOVED FROM THE BLEND FOR THIS REASON.
THE NAM IS DEEPER OVERALL, AS IT IS SLOWER TO SHEAR INTO THE
WESTERLIES, SO DESPITE ITS SIMILAR PLACEMENT COMPARED TO THE
PREFERRED CONSENSUS ITS STRENGTH MAKES IT AN OUTLIER. OTHERWISE,
THE 12Z NON-NCEP BLEND COMBINED WITH THE 18Z GEFS LEAVES A
SOLUTION THAT IS REASONABLE AND PREFERRED.
...BASE OF LONGWAVE TROUGH OVER THE NORTH-CENTRAL U.S. BY MONDAY
EVENING...
..RELATED COLD FRONT ACROSS THE UPPER MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/ECENS/UKMET AND 18Z GEFS
CONFIDENCE: AVERAGE
THE 00Z GFS IS TOO FAST WITH THE TROUGH AXIS DIGGING THROUGH THE
NORTHERN PLAINS, WHILE THE NAM IS ON THE OTHER END OF THE GUIDANCE
MAKING IT A SLOW OUTLIER. THE 12Z CMC IS GENERALLY IN GOOD
AGREEMENT WITH THE TIMING OF THE TROUGH AS IT PIVOTS EASTWARD, BUT
IT THE STRONGEST OF THE GUIDANCE AND DRIVES THE COLD FRONT FURTHER
SOUTH THAN THE PREFERRED CONSENSUS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
WEISS
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