286
FXUS10 KWNH 301654
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1253 PM EDT THU APR 30 2020
VALID APR 30/1200 UTC THRU MAY 04/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEEP TROUGH/CLOSED LOW IMPACTING THE EAST THROUGH FRIDAY AND
EARLY SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/EC ENSEMBLE MEAN/CMC BLEND
CONFIDENCE: AVERAGE
THE 12Z GFS CONTINUED TO BE ON THE FASTER SIDE OF THE GUIDANCE IN
BRINGING A SHORTWAVE ON THE EASTERN EDGE OF THE MID-LEVEL TROUGH
EJECTING OF THE EASTERN U.S. AS WELL AS BEING FASTER TO BRING A
SECOND VORTICITY CENTER TOWARDS NEW ENGLAND ON FRIDAY. THE NAM
WAS ALSO INCLINED TO STICK WITH ITS SOUTHWARD-DISPLACED TROUGH
LIKE IT SHOWED IN ITS 30/00Z RUN. BOTH FEATURES WERE OUTLIERS
WITH THE MID-LEVEL TROUGH AXIS BY 12Z SATURDAY COMPARED TO ALL OF
THE ECMWF/GEFS/CMC ENSEMBLE MEMBERS. REMOVED THE 30/00Z UKMET FROM
THE CHOICE GIVEN ITS VERY SLOW PROGRESSION.
...SHORTWAVE CROSSING THE NORTHWEST TODAY AND MOVING INTO WESTERN
ONTARIO SATURDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 30/00Z ECMWF/UKMET/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE GFS FROM THE 30/12Z RUN STILL STANDS OUT THE GREATEST WITH A
MORE AMPLIFIED AND SLOWER 500 MB SHORTWAVE TRACK BY MID-DAY
FRIDAY...WHICH STILL PUTS IT AT ODDS WITH TRENDS FROM THE 30/00Z
ECMWF AND 30/00Z CMC (THOSE NON-NCEP MODELS WERE SHOWING SOME
TRENDS TOWARD THAT GENERAL SOLUTION BUT THERE WERE JUST NOT AS
EXTREME). THE LOWER MID-LEVEL HEIGHTS IN THE GFS ALSO MADE IT
EASY FOR A SECOND SHORTWAVE ORIGINIATING IN NORTHERN SASKATCHEWAN
TO DROP SOUTHEASTWARD AND PRODUCE A DEEPENING CLOSED MID-LEVEL LOW
OVER ONTARIO AND QUEBEC BY EARLY SUNDAY. AT THIS POINT, THINKING
IS THAT A 30/00Z ECMWF/UKMET/CMC BLEND WILL INCORPORATE SOME OF
THESE IDEAS WHICH FALL BETWEEN THE NORTHERN AND FASTER 30/12Z NAM
AND SOUTHERN 30/12Z GFS.
...700-500 MB SHORTWAVE REACHING THE CENTRAL PLAINS SATURDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 30/00Z ECMWF/UKMET/CMC BLEND
CONFIDENCE: BELOW AVERAGE
THE 30/12Z NCEP RUNS WERE SIMILAR TO THEIR PREVIOUS RUNS...MEANING
THAT THEY WERE SOUTH WITH THIS FEATURE COMPARED WITH THE 30/00Z
RUNS OF NON-NCEP GUIDANCE. THE LATEST ENSEMBLE SPAGHETTI PLOTS
STILL OFFER MORE SUPPORT TO THE NON-NCEP GUIDANCE AT THIS POINT.
NO CHANGE TO THE OVERALL PREFERENCE WAS MADE. 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 30/00Z 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. DESPITE THE DECENT AGREEMENT FROM THE 30/00Z MODELS AND
THE 30/12Z RUN OF NCEP 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
BANN
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