477
FXUS10 KWNH 090429
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1228 AM EDT THU APR 09 2020
VALID APR 09/0000 UTC THRU APR 12/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLOSED LOW OVER NORTHEAST; DEEPENING SURFACE LOW OFF NEW ENGLAND
COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
ANOMALOUS CLOSED LOW CURRENTLY OVER NORTHERN GREAT LAKES WILL
DEEPEN AND TAKE A NEGATIVE TILT AS IT APPROACHES THE NORTHEAST
LATER TODAY WHILE AT THE SURFACE, LOW PRESSURE WILL MOVE TOWARD
THE EASTERN GREAT LAKES. A SECONDARY LOW WILL DEVELOP ALONG THE
I-95 CORRIDOR AND DEEPEN ALONG COASTAL MAINE. OVERALL, THE MASS
FIELDS HAVE COME INTO VERY GOOD AGREEMENT WITH THE EVOLUTION OF
THIS SYSTEM OVER THE NEXT 24-36 HOURS SUCH THAT A GENERAL MODEL
BLEND SHOULD SUFFICE.
SLOW MOVING CLOSED LOW ACROSS THE SOUTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/ECENS MEAN BLEND
CONFIDENCE: AVERAGE
LARGE, SLOW MOVING CUT-OFF SOUTHERN STREAM CLOSED LOW OVER
SOUTHERN CALIFORNIA IS EXPECTED TO GRADUALLY MOVE EASTWARD AS IT
INTERACTS WITH APPROACHING NORTHERN STREAM ENERGY ON DAY 3. UNTIL
THEN, MOVEMENT WILL BE SLOW AND OVER THE LAST SEVERAL MODEL
CYCLES, THE ECMWF HAS PROVEN TO BE MORE CONSISTENT. BOTH THE 18Z
GEFS AND 00Z GFS ARE FAST OUTLIERS WITH THE EJECTION OF THE
FEATURE INTO THE SOUTHERN PLAINS ON DAY 3, THOUGH IT IS WORTH
NOTING THAT THE 00Z GFS DID TREND SLOWER, AND IS NOW SLOWER THAN
THE 18Z GEFS MEAN, SO PERHAPS LATER RUNS OF THE GFS WILL CATCH ON
TO THE TREND. THE UKMET IS ALSO LESS FAVORED AS IT HAS ITS UPPER
LOW TOO FAR TO THE SOUTHWEST, AND DIGS FURTHER SOUTH INTO THE BAJA
REGION. OTHERWISE, A BLEND OF THE ECMWF/ECENS MEAN WITH SOME
INCLUSION OF THE CMC SEEMS LIKE A GOOD APPROACH FOR THIS SYSTEM
MASS FIELDS.
UPPER LEVEL TROUGH AND COLD FRONT REACHING THE NORTHWEST BY END OF
THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CMC/ECMWF/ECENS MEAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
SHORTWAVE ENERGY ALONG THE SOUTHERN COAST OF ALASKA WILL PROGRESS
EASTWARD TO THE YUKON TERRITORY, AND WITH THE ACCELERATING/EXITING
JET, THE UPSTREAM RIDGE WILL BREAK DOWN AND ALLOW FOR GREATER
PROPAGATION EAST AND THEN SOUTHWARD ACROSS SOUTHWESTERN CANADA.
THE HEIGHT-FALLS WILL OVERSPREAD THE LEE OF THE CANADIAN ROCKIES
AND THEN NORTHERN HIGH PLAINS, AND SUPPORT A SURFACE COLD FRONT TO
DROP SOUTHWARD ACROSS MONTANA AND THE DAKOTAS. SOME TIMING
DIFFERENCES ARE NOTED IN THE LATEST GUIDANCE, WHERE THE GFS/NAM
AND THE UKMET TO SOME DEGREE WHERE A BIT FASTER THAN THE 12Z
ECMWF/CMC. A LOOK AT THE LATEST ENSEMBLE MEANS, THE SLOWER TREND
WOULD BE FAVORED AND THE GFS/NAM ARE LIKELY TOO FAST WITH ITS
PROGRESSION OF THE COLD FRONT ACROSS THE NORTHERN PLAINS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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