931
FXUS10 KWNH 201641
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1140 AM EST THU FEB 20 2020
VALID FEB 20/1200 UTC THRU FEB 24/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...POSITIVELY TILTED MID LEVEL TROUGH AXIS APPROACHING THE EAST
COAST TONIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH THE POSITIVELY
TILTED TROUGH MOVING FROM THE MID MS VALLEY TO THE MID ATLANTIC
STATES TONIGHT INTO EARLY FRIDAY, AS THE TROUGH ELONGATES. AFTER
THAT TIME, THE 12Z GFS BECOMES FASTER THAN THE CONSENSUS, BUT BY
THAT TIME, THE TROUGH IS WELL OFFSHORE.
BOTH THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS AS THE SURFACE
WAVE FORMS OFF THE NC/SC COASTS THIS EVENING. THE 12Z GFS BECOMES
FASTER WITH THE SURFACE LOW AT THAT TIME (AND A BIT WEAKER), BUT
THIS IS NOT SURPRISING CONSIDERING THE MID LEVEL SUPPORT IS ALSO
FASTER. LATER IN THE PERIOD, THE 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN
BECOMES SLOWER THAN THE CONSENSUS, BUT BY THAT TIME, THE SENSIBLE
WEATHER SHOULD BE EXITING THE MID ATLANTIC COAST.
THEREFORE, A GENERAL MODEL BLEND IS PREFERRED WITH RESPECT TO THE
MASS FIELDS.
...CLOSED MID LEVEL LOW REACHING THE CENTRAL/SOUTHERN ROCKIES
SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/00Z UKMET/00Z CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH THE CLOSED MID
LEVEL LOW APPROACHING THE SOUTHWEST CA BY 22/12Z. AFTER THAT TIME,
BOTH MODELS BECOME FASTER THAN THE CONSENSUS AS THE MID LEVEL LOW
TRACKS ACROSS THE CENTRAL AND SOUTHERN ROCKIES INTO THE CENTRAL
PLAINS BY LATE SUNDAY. IN CONTRAST, THE 00Z NON-NCEP GUIDANCE IS
SLOWER WITH THE CLOSED LOW, KEEPING IT WEST OF THE NCEP CAMP BY
24/00Z.
MOST OF THE GUIDANCE (WITH THE EXCEPTION OF THE NAM) HAS BEEN
SLOWING WITH THIS FEATURE (AND ITS ATTENDANT SURFACE LOW),
INCLUDING THE 12Z GFS. BASED ON THE SLOWING, THE NON-NCEP GUIDANCE
IS PREFERRED, BUT GIVEN THE DICHOTOMY IN THE GUIDANCE, FORECAST
CONFIDENCE IS SLIGHTLY BELOW NORMAL.
..MID LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: AVERAGE
WHILE THE 12Z NAM IS CLOSE TO THE CONSENSUS WITH THE SHORT WAVE
NEAR 50N 150W AT 22/12Z, IT BECOMES MUCH SLOWER AS THAT SOLUTION
BUILDS MID LEVEL RIDGING AHEAD OF IT ACROSS CENTRAL AND NORTHERN
BRITISH COLUMBIA INTO SUNDAY. THE 00Z CMC IS ALSO SLOWER FOR THE
SAME REASON, BUT NOT NEARLY AS SLOW AS THE 12Z NAM.
THE 12Z GFS IS CLOSER TO THE CONSENSUS WITH THE SHORT WAVE ENERGY
AS IT CROSSES THE PACIFIC NORTHWEST DURING SUNDAY. THE 00Z UKMET
IS CLOSE TO THE 12Z GFS WITH RESPECT TO TIMING, BUT IS FLATTER
WITH THE WAVE AT THE END OF THE PERIOD. THE 00Z ECMWF/00Z ECWMF
MEAN IS A BIT DEEPER WITH THE SHORT WAVE BY 24/00Z THOUGH THE
TIMING IS CLOSE TO THE 12Z GFS/06Z GEFS MEAN.
OUTSIDE OF THE 12Z NAM, THERE IS REASONABLE AGREEMENT WITH THE
SHORT WAVE, SO A NON-12Z NAM BLEND IS PREFERRED.
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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