393
FXUS10 KWNH 171831
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EDT TUE MAR 17 2020
VALID MAR 17/1200 UTC THRU MAR 21/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP CLOSED MID LOW IMPACTING THE WEST
..CYCLOGENESIS OVER THE CENTRAL HIGH PLAINS WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE
OVERALL, THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH THE
CLOSED MID LEVEL LOW OVER COMING ASHORE OVER THE CENTRAL CA COAST
THIS AFTERNOON AND EVENING, TAKING IT TO A POSITION OVER THE GREAT
BASIN BY 20/12Z. BY THAT TIME, THE 12Z NAM BECOMES FASTER THAN THE
CONSENSUS, TAKING THE MID LEVEL LOW OVER THE FOUR CORNERS WHEN THE
REMAINDER OF THE GUIDANCE IS STILL OVER CA/NV. IN CONTRAST, THE
12Z GFS REMAINS CLOSER TO THE CONSENSUS, AS IT SPINS DOWN OVER THE
GREAT BASIN BEFORE 21/00Z.
THERE IS STILL A FAIR AMOUNT OF SPREAD ON THE POSITION OF THE
SURFACE WAVE THAT FORMS OVER EASTERN CO EARLY THU, THOUGH THE 12Z
NAM/GFS ARE CLOSE TO THE CONSENSUS THROUGH 20/00Z. AFTER THAT
TIME, THE 12Z NAM BECOMES FASTER AND FURTHER NORTH INTO THE COLD
AIR (A KNOWN NAM BIAS) AS THE SURFACE LOW TRACK ACROSS THE UPPER
GREAT LAKES BEYOND 20/00Z. TOWARD THE END OF THE PERIOD, THE 12Z
GFS (AS WELL AS THE 06Z GEFS MEAN) BECOME FASTER THAN THE
CONSENSUS TAKING THE SURFACE LOW THROUGH QUEBEC. BY THAT TIME,
MUCH OF THE SENSIBLE WEATHER REMAINS OVER QUEBEC, SO THE
DIFFERENCES ARE NOT AS IMPACTFUL.
BASED ON THE ABOVE, A BLEND OF THE 12Z GFS/00Z ECMWF IS PREFERRED
WITH THIS SYSTEM. BECAUSE OF THE SPREAD IN THE MID LEVEL SYSTEM,
AS WELL AS THE SURFACE SYSTEM LATE, FORECAST CONFIDENCE IS ONLY
AVERAGE.
..MID LEVEL TROUGH ARRIVING OVER THE NORTHERN HIGH PLAINS WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z NAM BLEND
CONFIDENCE: ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS BRINGING AN EVOLVING
MID LEVEL TROUGH FROM CENTRAL MANITOBA AT 19/12Z TO A POSITION
OVER THE UPPER GREAT LAKES BY 20/12Z. AFTER THAT TIME, THE 12Z NAM
BECOMES SLOWER THAN THE CONSENSUS, AS EACH OF THE OTHER MEMBERS OF
THE CONSENSUS SHOWING THE SYSTEM SPEEDING UP WITH TIME AS IT
CROSSES ONTARIO INTO QUEBEC BY THE END OF THE PERIOD. WITH ONLY
THE 12Z NAM NOT CLOSE TO THE TIGHTLY CLUSTERED SOLUTION WITH THIS
SYSTEM, A NON-12Z NAM SOLUTION IS PREFERRED WITH ABOVE AVERAGE
FORECAST CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAYES
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