003
FXUS10 KWNH 261635
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1134 AM EST WED FEB 26 2020
VALID FEB 26/1200 UTC THRU MAR 01/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS MODEL EVALUATION WITH INITIAL PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..EASTERN HALF OF NORTH AMERICA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING THE LEAD SHORT
WAVE IN THE EVOLVING LONG WAVE TROUGH FROM WESTERN TN INTO WESTERN
PA THIS EVENING, BEFORE CLOSING OFF OVER ONTARIO/QUEBEC AFTER
28/00Z. SECONDARY SURFACE DEVELOPMENT OCCURS AT THE TRIPLE POINT
OF THE LENGTHENING OCCLUSION OVER THE SOUTHWEST ME COAST AFTER
27/18Z. THERE IS GOOD MODEL CONSENSUS WITH FAIRLY TIGHT CLUSTERING
WITH THE SURFACE LOW THROUGH THIS TIME.
AS THE MID LEVEL SYSTEM CLOSES OFF OVER QUEBEC/NORTHERN ME THROUGH
THE END OF THE PERIOD, THERE IS SOME SPREAD ON THE TRACK OF THE
WEAKENING SURFACE LOW MOVING ACROSS THE SAME AREA. THE 12Z GFS IS
THE WESTERNMOST SOLUTION IN THE ENVELOPE BY 01/00Z, THOUGH BY THIS
TIME MUCH OF THE SENSIBLE WEATHER REMAINS IN QUEBEC. WITH THE
INCREASING MODEL AGREEMENT, A GENERAL MODEL BLEND IS PREFERRED,
THOUGH SOME SPREAD AT THE END OF THE FORECAST PERIOD KEEPS
FORECAST CONFIDENCE AT AVERAGE.
..WESTERN U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GFS BLEND
CONFIDENCE: AVERAGE
EVOLVING SHORT WAVE ENERGY NEAR 46N 154W AFTER 27/12Z ATTEMPTS TO
CLOSE OFF AS IT APPROACHES WA STATE AFTER 29/00Z, BEFORE TRACKING
INTO ALBERTA/MANITOBA BY THE END OF THE PERIOD. THE 12Z GFS IS
FASTER THAN THE CONSENSUS WITH THE SHORT WAVE ALMOST IMMEDIATELY,
WITH THE GREATEST DIFFERENCE IN TIMING OCCURRING AS IT REACHES THE
PACIFIC NORTHWEST AFTER 29/00Z. THE 00Z NAM, BY CONTRAST, REMAINS
CLOSER TO THE CONSENSUS THROUGHOUT THE PERIOD.
AFTER BRIEFLY CLOSING OFF A MID LEVEL CIRCULATION OVER VANCOUVER
ISLAND NEAR 29/00Z (WHICH THE 12Z NAM DOES 6 HOURS LATER), THE 12Z
GFS BEGINS SLOWING AS IT ENCOUNTERS MID LEVEL RIDGING OVER THE
NORTHERN ROCKIES AND WEST CENTRAL CANADA. BY 01/00Z, THE 12Z GFS
REJOINS THE PACK WITH THE MID LEVEL FEATURE AND SURFACE LOW OVER
SOUTHERN MANITOBA.
BECAUSE OF ITS FASTER SOLUTION THROUGH THE FIRST HALF OF THE
FORECAST PERIOD, THE 12Z GFS IS OMITTED FROM THE PREFERENCE. SOME
SPREAD IN THE PLACEMENT OF THE SURFACE LOW LATE, IN ADDITION TO
THE TIMING ISSUES WITH THE 12Z GFS, RESULTS IN 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
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