912
FXUS10 KWNH 251835
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EST TUE FEB 25 2020
VALID FEB 25/1200 UTC THRU FEB 29/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..EASTERN HALF OF NORTH AMERICA
PREFERENCE: BLEND OF 12Z NAM/ECMWF/UKMET
CONFIDENCE: AVERAGE
GRADUAL PHASING OF NORTHERN AND SOUTHERN STREAMS WILL LEAD TO
MATURE CYCLONE DEVELOPMENT OVER THE NORTHEASTERN U.S. AND
SOUTHEAST CANADA BY THURSDAY. THE THEN-MATURE, FULL LATITUDE
TROUGH WILL OCCUPY THE EASTERN U.S. FOR ANOTHER DAY OR TWO.
THE MODELS ARE ALL GENERALLY AGREEABLE ALOFT. THE MAIN DEVIANT
MODEL, AS NOTED OVERNIGHT, WAS THE 00Z CANADIAN WITH ITS MORE
FULLY DEVELOPED COASTAL LOW. THIS CORRECTED ON THE 12Z RUN,
ALTHOUGH THE CANADIAN NOW LIFTS THE PRIMARY LOW CENTER FARTHER
NORTHWEST INTO QUEBEC COMPARED TO OTHER GUIDANCE. MOST SOLUTIONS
DO HAVE A SEMBLANCE OF A DOUBLE-BARREL LOW, WITH THE PRIMARY
TRACKING INTO QUEBEC, AND ANOTHER LOW ATTEMPTING TO FORM ALONG THE
COAST FROM MAINE TO THE CANADIAN MARITIMES.
IN THE 12Z CYCLE WHAT STANDS OUT IS A SUDDEN AND STARK DEEPENING
TREND IN THE GFS, WHICH TAKES THE PRIMARY SURFACE LOW DOWN TO 983
MB AT 28/00Z. THE 12Z GEFS MEAN SUPPORTED THIS TO A DEGREE, AND
EVEN THE ECMWF DID OFFER A DEEPER SURFACE LOW THAN BEFORE, BUT THE
GFS IS MORE GREATLY DEVELOPED AT ALL LEVELS, PRODUCING 500-MB
HEIGHTS THAT ARE 60 METERS COLDER THAN THE OTHER MODELS ON
THURSDAY. THE GFS GETS THERE BY MEANS OF A SHARPER, MORE ENERGETIC
WAVE EMERGING FROM THE SOUTHERN ROCKIES THIS EVENING. ALTHOUGH
500-250 MB OBSERVED WINDS WERE IMPRESSIVE AT ALBUQUERQUE AND
AMARILLO THIS MORNING, THERE DOES NOT APPEAR TO BE ANYTHING
ESPECIALLY IMPRESSIVE ABOUT THIS WAVE, AND THE FACT THAT THE NAM -
WHOSE BIAS IS STRONG AND DEEP - DOES NOT SUPPORT THIS TREND,
PERHAPS SPEAKS VOLUMES. WE THEREFORE PREFER THE NAM ALONG WITH THE
CONSISTENT ECMWF AND UKMET.
..WESTERN U.S
PREFERENCE: 12Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE
A MINOR SHORTWAVE TROUGH WILL SCOOT THROUGH THE NORTHWEST U.S.
TODAY AND TOMORROW. THEN EXPECT A BUILDING SHORTWAVE RIDGE IN
ADVANCE OF WHAT LOOKS LIKE A DAY 4 SYSTEM TO ARRIVE FRIDAY NIGHT /
SATURDAY. THE NCEP SOLUTIONS HAVE BEEN NOTICEABLY MUCH FASTER THAN
THE OTHER GLOBAL GUIDANCE IN BRINGING THE NEXT WAVE TOWARD THE
COAST ON FRIDAY. ON THE OTHER HAND, THE 00Z UKMET AND NOW THE 12Z
CANADIAN SET THE SLOW AND STRONG SIDE OF THE ENVELOPE (NOTE THAT
THE 12Z UKMET WAS RADICALLY DIFFERENT THAN THE 00Z). WAVE SPACING
ACROSS THE PACIFIC SUGGEST A TROUGH ABOUT IN THE POSITION OF THE
ECMWF SOLUTION AT 29/00Z, AND THAT MODEL HAS BEEN THE MOST
CONSISTENT OVER THE LAST COUPLE OF RUNS. THIS IS OUR PREFERENCE,
NOTING THAT THE GFS DID TREND A BIT TOWARD THIS PREFERENCE WHILE
STILL LOOKING A TAD FAST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
BURKE
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