185
FXUS10 KWNH 300737
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 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 MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP TROUGH/CLOSED LOW IMPACTING THE EAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/CMC 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 SATURDAY 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 00Z
ECMWF/UKMET/CMC ARE IN GOOD AGREEMENT WITH THIS SYSTEM AND MATCH
CLOSER TO THE MIDDLE OF THE LATEST ENSEMBLE SPREAD WITH THE UPPER
TROUGH EVOLUTION.
...SHORTWAVE CROSSING THE NORTHWEST TODAY AND MOVING INTO WESTERN
ONTARIO SATURDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/CMC BLEND
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 00Z UKMET JUMPED NORTH WITH
THE TRACK OF THE VORTICITY MAX. HOWEVER, TRENDS FROM THE 00Z ECMWF
AND 00Z CMC WERE IN THE DIRECTION OF THE 00Z GFS (JUST NOT AS
EXTREME) AND SO THE 00Z NAM APPEARS TO BE LESS FAVORABLE AT THIS
TIME. A 00Z ECMWF/UKMET/CMC BLEND WILL INCORPORATE SOME OF THESE
NEW TRENDS WHICH FALL BETWEEN THE NORTHERN AND FASTER 00Z NAM AND
SOUTHERN/SLOWER 00Z GFS.
...700-500 MB SHORTWAVE REACHING THE CENTRAL PLAINS SATURDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/CMC BLEND
CONFIDENCE: BELOW AVERAGE
NO SIGNIFICANT CHANGES WERE NOTED WITH THE 00Z ECMWF/UKMET/CMC
REGARDING THIS FEATURE. 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 00Z 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: NON 00Z UKMET BLEND
CONFIDENCE: AVERAGE
ENSEMBLE MEANS SUPPORT A NON 00Z UKMET BLEND WITH THE APPROACHING
LARGE TROUGH/CLOSED LOW OFFSHORE OF THE PACIFIC NORTHWEST EARLY
SATURDAY. THE 00Z UKMET IS FASTER THAN THE REMAINING CONSENSUS AND
THE 00Z CMC ADJUSTED THE BASE OF THE TROUGH (COMPARED TO ITS 12Z
RUN) TO FIT INTO THE NON 00Z UKMET CONSENSUS. DESPITE THE DECENT
AGREEMENT FROM THE 00Z MODELS, ENSEMBLE SPAGHETTI PLOTS STILL SHOW
SOME SPREAD AND ROOM FOR FUTURE ADJUSTMENTS WITH LATER
DETERMINISTIC GUIDANCE.
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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