907
FXUS10 KWNH 010455
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 AM EDT FRI MAY 01 2020
VALID MAY 01/0000 UTC THRU MAY 04/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEEP TROUGH/CLOSED LOW IMPACTING THE EAST THROUGH FRIDAY AND
EARLY SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
ONLY MINOR TIMING DIFFERENCES REMAIN WITH THIS SYSTEM BUT
AGREEMENT IS NOW SUFFICIENT TO SUPPORT A GENERAL MODEL BLEND.
...SHORTWAVE/SURFACE LOW TRACKING NEAR THE U.S./CANADIAN BORDER
THROUGH SUNDAY NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 00Z GFS HAS BACKED AWAY FROM ITS PREVIOUS (12 & 18Z CYCLES)
RUNS SHOWING A MORE AMPLIFIED 500 MB SHORTWAVE OVER
MANITOBA/ONTARIO FRIDAY NIGHT. HOWEVER, THE 00Z NAM APPEARS TO BE
A NORTHERN OUTLIER WITH THE SHORTWAVE AND SURFACE LOW, WITH THE
ENSEMBLE SCATTER LOW PLOTS SUPPORTING A NON-00Z NAM BLEND.
REGARDING TIMING, THE 00Z NAM/GFS ARE QUICKER TO PROGRESS AN
ASSOCIATED COLD FRONT TOWARD THE SOUTH AND EAST WHILE THE 12Z
ECMWF/UKMET/CMC ARE SLOWER. A BLENDED APPROACH IS RECOMMENED AT
THIS TIME WITH DIFFERENCES BECOMING SMALLER BY SUNDAY.
...700-500 MB SHORTWAVE REACHING THE CENTRAL PLAINS SATURDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 00Z GFS CONTINUES TO LOOK TOO AMPLILFIED WITH THIS FEATURE
EXITING THE ROCKIES INTO THE GREAT PLAINS ON SATURDAY. SINCE
YESTERDAY, THE LATEST ENSEMBLE GUIDANCE HAS TRENDED TOWARD THE
MIDDLE OF THE DEEPER GFS AND FLATTER NON-NCEP CAMP. CURRENLTY THE
MIDDLE GROUND IS FAVORED AND THAT IS BETWEEN THE 00Z NAM AND 12Z
ECMWF. THE FASTER 00Z NAM MAY NOT BE WRONG GIVEN THE ZONAL FLOW
THAT SETS UP ACROSS THE LOWER 48 IN THE WAKE OF THE DEPARTING EAST
COAST TROUGH AXIS. CONVECTIVE UNCERTAINTY CONTINUES TO LOWER
CONFIDENCE WITH THIS FEATURE.
...DEEP TROUGH OFFSHORE THE WEST COAST TODAY AND SATURDAY WITH
REMNANT SHORTWAVE ENERGY MOVING THROUGH THE NORTHWEST SUNDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
MODEL DIFFERENCES ARE SMALL ENOUGH AT THIS POINT TO RECOMMEND A
GENERAL MODEL BLEND.
...POTENTIAL MID-LEVEL SHORTWAVE REACHING THE WEST COAST ON
SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF MEAN
CONFIDENCE: BELOW AVERAGE
WHILE THERE ARE SOME DIFFERENCES AMONG THE DETERMINISTIC GUIDANCE,
MOST AGREE THAT A 500 MB SHORTWAVE WILL REACH THE NORTHERN CA
COAST SUNDAY AFTERNOON OR EARLY EVENING. THE 00Z GFS APPEARS TOO
FAST AND DEEP COMPARED TO THE REMAINING AVAILABLE
DETERMINISTIC/ENSEMBLE GUIDANCE. THE 12Z ECMWF AND 12Z CMC ARE
FLAT WITH THIS FEATURE WHILE THE 12Z UKMET IS FASTER/WEAKER AND
NORTH. ENSEMBLE MEANS SUPPORT SOMEWHERE BETWEEN THE SOMEWHAT
STRONGER 00Z NAM AND FLATTER ECMWF/CMC. THEREFORE, A BLEND OF THE
12Z ECMWF MEAN AND 00Z NAM IS PREFERRED THROUGH THE END OF THE
SHORT RANGE PERIOD (12Z/04).
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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