009
FXUS10 KWNH 210447
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 AM EDT TUE APR 21 2020
VALID APR 21/0000 UTC THRU APR 24/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEVELOPING LONG WAVE TROUGH OVER NEW ENGLAND WITH AN ASSOCIATED
SURFACE LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH SHORT WAVE ENERGY
TRACKING FROM MANITOBA ACROSS THE THE UPPER MS VALLEY, WHICH THEN
DROPS INTO THE BOTTOM OF A DEVELOPING LONG WAVE TROUGH HEADED FOR
NEW ENGLAND AFTER 21/12Z. THE SHORT WAVE TAKES THE LONG WAVE
TROUGH NEGATIVE ACROSS NEW ENGLAND AND NEARBY QUEBEC, AS A CLOSED
LOW FORMS OVER SOUTH CENTRAL QUEBEC. THESE SOLUTIONS ARE ALSO
CLOSE TO THE CONSENSUS WITH THE DEVELOPING SURFACE LOW OVER
QUEBEC. IN GENERAL, THERE IS GOOD MODEL AGREEMENT WITH THE MID
LEVEL AND SURFACE FEATURES, SO A GENERAL MODEL BLEND IS PREFERRED
WITH THIS SYSTEM, WITH ABOVE AVERAGE FORECAST CONFIDENCE.
...MID LEVEL TROUGH TRACKING FROM ACROSS THE SOUTHWEST AND
SOUTHERN PLAINS TO THE MID ATLANTIC...
..SURFACE LOW ASSOCIATED WITH THE MID LEVEL TROUGH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS TAKING THE SHORT WAVE
ENERGY OVER SOUTHERN CA EARLY IN THE PERIOD ACROSS THE SOUTHERN
PLAINS BEFORE 22/12Z. AFTER THAT TIME, THE 00Z NAM BECOMES SLOWER
THAN THE CONSENSUS, CLOSING OFF A MID LEVEL LOW OVER AR (THOUGH
NOT QUITE AS SLOW AS THE 12Z UKMET, WHICH HAS BEEN CONSISTENTLY
SLOW WITH THE FEATURE FOR THE PAST THREE MODEL CYCLES). THE 00Z
NAM IS ALSO SLOWER WITH THE SURFACE LOW ACROSS THE SOUTHERN PLAINS
INTO THE LOWER MS VALLEY DURING THIS TIME.
BY CONTRAST, THE 00Z GFS IS CLOSE TO THE 12Z ECMWF WITH THE TIMING
OF THE SHORT WAVE, AS WELL AS THE TRACK OF THE SURFACE LOW THROUGH
23/12Z, AND HAVE THEIR RESPECTIVE ENSEMBLE MEANS SUPPORTING THEIR
SOLUTIONS. THE 12Z CMC, WHILE SLOWER WITH THE MID LEVEL AND
SURFACE SYSTEMS THAN THE 00Z
GFS/12Z ECMWF CONSENSUS, IS ALSO USABLE FOR THIS SYSTEM ACROSS THE
MID MS VALLEY.
THERE IS SOME MODEL SPREAD AS THE SURFACE LOW TRACKS OFF THE MID
ATLANTIC COAST LATE IN THE PERIOD, AS THE 12Z ECMWF/12Z ECMWF
ENSEMBLE MEAN BECOME FASTER THAN THE 00Z GFS/12Z GEFS MEAN, THIS
IS TIED TO THE SPEED OF THE MID LEVEL SUPPORT EXITING THE MID
ATLANTIC COAST, AS THE 00Z GFS TENDS TO BUILD A STRONGER SHORT
WAVE RIDGE ACROSS THE MID ATLANTIC, SLOWING THE PROGRESS OF THE
SURFACE SYSTEM. FOR MUCH OF THE PERIOD, THE 00Z GFS/12Z ECMWF ARE
SOLID AS A PREFERRED SOLUTION, WITH SPREAD TOWARD THE END OF THE
PERIOD REDUCING FORECAST CONFIDENCE WITH TIME. BECAUSE OF THIS,
FORECAST CONFIDENCE IS ONLY AVERAGE.
...SHORT WAVE AND SURFACE LOW TRACKING FROM WESTERN CANADA TO THE
NORTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z UKMET BLEND
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS TRACKING SHORT WAVE
ENERGY FROM WESTERN CANADA IN THE VERY FAST MID LEVEL FLOW ACROSS
THE NORTHERN PLAINS BEFORE 23/00Z. THE 00Z NAM BECOMES SLOWER THAN
THE 00Z GFS AFTER THIS TIME, EVENTUALLY PLACING THE TROUGH OVER
WESTERN ND (AS DOES THE 12Z CMC). THE 00Z GFS IS CLOSE TO THE 12Z
ECMWF/UKMET WITH THE TROUGH POSITION EXTENDING FROM ND SOUTH
THROUGH NE BY 24/12Z. THERE IS MORE SPREAD WITH THE PLACEMENT OF
THE RESULTING SURFACE LOW FROM ND INTO NE. SINCE THERE HAS BEEN
SOME CONSISTENCY WITH THE 00Z GFS/12Z ECMWF/12Z UKMET WITH THIS
FEATURE, THESE MODELS COMPRISE THE PREFERRED BLEND. HOWEVER, DUE
TO THE SLOWER SOLUTIONS OF THE 00Z NAM/12Z CMC AND THE SPREAD IN
THE PLACEMENT OF THE SURFACE LOW AT THE END OF THE PERIOD,
FORECAST CONFIDENCE IS ONLY AVERAGE.
...SHORT WAVE ENERGY TRACKING FROM THE PACIFIC NORTHWEST TO THE
SOUTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS ARE CLOSE TRACKING SHORT WAVE ENERGY FROM WA/OR
AFTER 23/00Z IN THE FAST MID LEVEL FLOW TO A POSITION OVER THE
WESTERN HIGH PLAINS BY THE END OF THE PERIOD. THEY FORM A LOOSE
CLUSTER WITH MUCH OF THE 12Z GUIDANCE WITH THE SHORT WAVE, AND ITS
ASSOCIATED SURFACE LOW DEVELOPING OVER NORTHERN AND CENTRAL TX
(WITH THE 12Z UKMET A BIT SLOWER WITH THE SURFACE LOW AT 24/12Z).
SINCE THERE GENERALLY GOOD MODEL AGREEMENT WITH THE MID LEVEL AND
SURFACE SYSTEMS, A GENERAL MODEL BLEND IS PREFERRED. GIVEN THE
SPEED OF THE MID LEVEL FLOW, IT IS NOT YET CLEAR IF SMALLER SCALE
INTERACTIONS MIGHT YET RESULT IN MORE INSTABILITY IN THE TIMING OF
THE MID LEVEL AND SURFACE SYSTEMS. BECAUSE OF THIS, FORECAST
CONFIDENCE IS JUST AVERAGE.
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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