698
FXUS10 KWNH 300520
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
120 AM EDT THU APR 30 2020
VALID APR 30/0000 UTC THRU MAY 03/1200 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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
THE 00Z NAM DIGS THE CENTER OF THE CLOSED LOW IMPACTING THE
EASTERN U.S. FARTHER SOUTH THAN ANY OTHER GUIDANCE WHICH RESULTS
IN A SLOWER AND SOUTHWARD DISPLACED 500 MB TROUGH IN THE NAM BY
EARLY SATURDAY. THE 00Z NAM IS A TOTAL OUTLIER WITH THE MID-LEVEL
TROUGH AXIS BY 12Z SATURADY COMPARED TO ALL OF THE ECMWF/GEFS/CMC
ENSEMBLE MEMBERS. THE 00Z GFS IS FASTER WITH A LEAD VORTICITY MAX
LOCATED ON THE EASTERN EDGE OF THE MID-LEVEL TROUGH AXIS FRIDAY
MORNING WHICH WHEN COMBINED WITH A FASTER SHORTWAVE TROUGH AXIS
APPROACHING NORTHERN NEW ENGLAND FRIDAY NIGHT CAUSES THE LOWER
LEVELS OF THE 00Z GFS TO FALL OUT OF ALIGNMENT WITH THE REMAINING
MODEL CONSENSUS AND MIDDLE GROUND 12Z ECMWF ENSEMBLE MEAN. THE 12Z
CMC IS PERHAPS A SECONDARY OPTION FOR THE EAST, BUT ITS SECONDARY
SURFACE LOW LOCATED NEAR/SOUTH OF LONG ISLAND FRIDAY NIGHT IS ON
THE STRONG SIDE OF THE LATEST MODEL CONSENSUS. THE PREFERENCE WILL
BE TOWARD THE SIMILAR 12Z ECMWF/UKMET AT THIS TIME.
...SHORTWAVE CROSSING THE NORTHWEST TODAY AND MOVING INTO WESTERN
ONTARIO SATURDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM, 12Z ECMWF AND 12Z CMC
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 00Z GFS STANDS OUT THE GREATEST WITH A MORE AMPLIFIED AND
SLOWER 500 MB SHORTWAVE TRACK BY MID-DAY FRIDAY. THE 12Z UKMET IS
SOMEWHAT SIMILAR TO THE GFS, BUT THE ENSEMBLE MEANS AND LOW PLOT
CLUSTERING DOES NOT SUPPORT THE GFS/UKMET SOLUTIONS. THE 00Z NAM,
12Z ECMWF AND 12Z CMC LOOK BEST WITH THIS SYSTEM.
...700-500 MB SHORTWAVE REACHING THE CENTRAL PLAINS SATURDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET/CMC
CONFIDENCE: BELOW AVERAGE
A SUBTLE LOW TO MID-LEVEL SHORTWAVE IS EXPECTED TO REACH THE
CENTRAL PLAINS EARLY SATURDAY WITH AN AXIS OF 700 MB CONVERGENCE
INTO THE GREAT PLAINS. THE 00Z NAM/GFS ARE SOUTH WITH THIS FEATURE
COMPARED TO THE 12Z ECMWF/UKMET/CMC. 500 MB HEIGHTS FROM THE
LATEST ENSEMBLE SPAGHETTI PLOTS SUPPORT THE NORTHERN NON-NCEP CAMP
MORE SO THAN THE NAM/GFS. THIS FEATURE WILL BE OCCURRING IN A
POST-FRONTAL ENVIRONMENT WITH UPSLOPE FLOW JUST ABOVE THE SURFACE.
CONVECTIVE UNCERTAINTY LOWERS CONFIDENCE WITH THIS FEATURE BUT A
SOUTHERN PLAINS SURFACE LOW NOW SHOWS GOOD MODEL AGREEMENT FROM
THE LATEST AVAILABLE MODELS.
..DEEP TROUGH OFFSHORE THE WEST COAST BY SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM, 00Z GFS, 12Z ECMWF BLEND
CONFIDENCE: AVERAGE
ENSEMBLE MEANS SUPPORT A GENERAL BLEND OF THE 00Z NAM, 00Z GFS AND
12Z ECMWF WITH THE APPROACHING LARGE TROUGH/CLOSED LOW OFFSHORE OF
THE PACIFIC NORTHWEST EARLY SATURDAY. THE TIMING OF SHAPE OF THE
TROUGH NOTED FROM THE 12Z UKMET/CMC IS NOT SUPPORTED FROM THE
ENSEMBLES AT THIS TIME.
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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