178
FXUS10 KWNH 281836
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT TUE APR 28 2020
VALID APR 28/1200 UTC THRU MAY 02/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEVELOPING LONG WAVE TROUGH AND SURFACE LOW TRACKING FROM THE
MID MS VALLEY TO THE NORTHERN MID ATLANTIC...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z GFS BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 12Z NAM/GFS ARE CLOSE WITH SHORT WAVE ENERGY TRACKING FROM
EASTERN MT THAT DROPS INTO A DEVELOPING LONG WAVE TROUGH ACROSS
THE MID MS VALLEY THROUGH 30/00Z. AFTER THAT TIME, THE 00Z NAM
BECOMES SLOWER THAN THE CONSENSUS, WITH THE GREATEST DIFFERENCE
OCCURRING OVER THE NORTHERN MID ATLANTIC TOWARD THE END OF THE
PERIOD. THE 12Z GFS REMAINS CLOSER TO THE CONSENSUS AS THE CLOSED
MID LEVEL SYSTEM CROSSES THE OH VALLEY, THEN BECOMES FASTER WITH
THIS SYSTEM BY 02/00Z. THE DIFFERENCES WITH THE 12Z NAM APPEAR TO
BE DRIVEN BY HOW THE CLOSED MID LEVEL SYSTEM INTERACTS WITH SHORT
WAVE ENERGY DROPPING INTO IT ACROSS THE OH VALLEY AND NORTHERN MID
ATLANTIC. BY CONTRAST, THE 12Z ECMWF HAS BEEN MORE CONSISTENT WITH
THE MID LEVEL SYSTEM.
THE 12Z NAM ALSO EXHIBITS ISSUES WITH THE SURFACE LOW ASSOCIATED
WITH THE MID LEVEL SYSTEM, WITH THE 12Z GFS CLOSER TO THE 12Z
ECWMF BY 02/00Z. THOUGH THE 12Z ECMWF/GFS FORM A LOOSE CONSENSUS
WITH THE SURFACE SYSTEMS, THERE REMAINS A FAIR AMOUNT OF SPREAD IN
THE SOLUTIONS (AS SEEN IN THE 12Z GEFS/00Z ECMWF ENSEMBLE MEAN,
WHICH ARE FURTHER NORTH WITH THE SURFACE SYSTEM). BASED ON THIS,
FORECAST CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE.
...SHORT WAVE ENERGY AFFECTING THE PACIFIC NORTHWEST TO THE
NORTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING SHORT WAVE
ENERGY NEAR 42N 138W AT 29/12Z AND WEAKENING IT AS IT APPROACHES
VANCOUVER ISLAND NEAR 30/12Z. AFTER THIS TIME, BOTH MODELS DIVERGE
FROM THE LOOSE CONSENSUS, WITH THE 12Z NAM TAKING THE BULK OF THE
SHORT WAVE ENERGY INTO ALBERTA AND MANITOBA. THE 12Z GFS REMAINS
CLOSER TO THE 12Z ECMWF/00Z ECMWF ENSEMBLE MEAN, KEEPING THE SHORT
WAVE ENERGY CLOSER TO THE INTERNATIONAL BORDER, REACHING THE
NORTHERN PLAINS BEFORE 02/00Z. SOME OF THE SPREAD COULD BE TIED TO
HOW A SECOND SHORT WAVE APPROACHING THE PACIFIC NORTHWEST LATE
INTERACTS WITH THE FIRST SHORT WAVE, CAUSING SOME DIVERGENCE IN
THE SOLUTIONS.
BASED ON THE INCREASING SPREAD WITH TIME, FORECAST CONFIDENCE IS
SLIGHTLY BELOW AVERAGE.
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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