706
FXUS10 KWNH 210639
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 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 MODEL EVALUATION WITH FINAL 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/00Z 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 00Z 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 00Z 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 00Z CMC CONTINUED TO SLOW ITS MID LEVEL TROUGH AND
SURFACE WAVE, SO MUCH SO THAT IS PROBABLY NO LONGER A VIABLE
SOLUTION 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 00Z ECMWF/12Z ECMWF
ENSEMBLE MEAN REMAIN FASTER THAN THE 00Z GFS/00Z GEFS MEAN. THIS
SEEMS TO BE 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/00Z 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/00Z ECMWF/00Z 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 00Z CMC, THOUGH NOT AS FAR WEST AS THE 00Z
NAM). THE 00Z GFS IS CLOSE TO THE 00Z 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/00Z ECMWF/00Z UKMET WITH THIS FEATURE, THESE MODELS COMPRISE
THE PREFERRED BLEND. HOWEVER, DUE TO THE SLOWER SOLUTIONS OF THE
00Z NAM/00Z 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 00Z GUIDANCE WITH THE SHORT WAVE, AND ITS
ASSOCIATED SURFACE LOW DEVELOPING OVER NORTHERN AND CENTRAL TX.
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 SIMPLY 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page