791
FXUS10 KWNH 280643
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT TUE APR 28 2020
VALID APR 28/0000 UTC THRU MAY 01/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7Z UPDATE: THE 00Z ECMWF TRENDED A LITTLE DEEPER WITH THE CLOSED
LOW THAT DEVELOPS OVER MICHIGAN ON THURSDAY AND SLIGHTLY STRONGER
WITH THE EVOLVING TRIPLE POINT LOW NEAR THE MID-ATLANTIC FRIDAY
MORNING. THE CMC ALSO TRENDED A LITTLE MORE AMPLIFIED BY THE END
OF THE FORECAST PERIOD ACROSS THE SOUTHEAST STATES. THE UKMET IS
CLOSER TO THE MODEL CONSENSUS WITH THE SURFACE LOW NEAR LAKE
MICHIGAN WEDNESDAY MORNING COMPARED TO ITS 12Z RUN, AND MAINTAINED
GOOD CONTINUITY ALOFT. BY FRIDAY MORNING, THE CMC IS ON THE
SOUTHERN EDGE OF THE GUIDANCE WITH THE LOW, AND THE GFS DISPLACED
TO THE NORTH. THERE IS ENOUGH AGREEMENT AMONG THE UKMET, ECMWF,
AND NAM TO MERIT A BLEND OF THESE MODELS FOR THIS DEVELOPING STORM
SYSTEM.
DEPARTING NORTHEAST STORM SYSTEM THROUGH TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
THE EXITING COASTAL LOW FROM NEW ENGLAND WILL PASS SOUTH OF NOVA
SCOTIA THROUGH TUESDAY AS IT CONSOLIDATES INTO A STRONGER LOW
SOUTH OF NEWFOUNDLAND BY TUESDAY NIGHT. DETERMINISTIC MODEL
SPREAD IS MINIMAL AND THEREFORE A GENERAL MODEL BLEND WILL
CONTINUE TO WORK WELL FOR THIS REGION.
STRONG STORM SYSTEM DEVELOPING OVER THE NORTH-CENTRAL U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/NAM
CONFIDENCE: MODERATE
A NORTHERN STREAM SHORTWAVE TROUGH IS AMPLIFYING ACROSS MONTANA
AND THE DAKOTAS IN RESPONSE TO A DEEP LAYER RIDGE DEVELOPING OVER
THE WESTERN U.S. AND SOUTHWEST CANADA, AND THIS WILL CONTINUE
GOING THROUGH THE MIDDLE OF THE WEEK. A WELL DEVELOPED CLOSED LOW
IS FORECAST TO EVOLVE OVER THE MIDWEST AND THEN THE SOUTHERN GREAT
LAKES BY WEDNESDAY NIGHT AS A DEEP LAYER TROUGH ENVELOPS MUCH OF
THE EASTERN U.S. BY THAT TIME PERIOD. ALL OF THE MODELS SHOW
REASONABLY GOOD AGREEMENT WITH THE UPPER LEVEL EVOLUTION AND
SURFACE CYCLOGENESIS GOING THROUGH WEDNESDAY MORNING. BY EARLY
THURSDAY, SOME LATITUDINAL DIFFERENCES BECOME APPARENT AS THE 00Z
NAM/GFS SOLUTIONS HAVE THE SURFACE LOW OVER CENTRAL MICHIGAN, AND
THE 12Z NON-NCEP SOLUTIONS TENDING TO KEEP THE LOW FARTHER TO THE
SOUTHEAST, AND WITH A BIT BETTER DEFINED TRIPLE-POINT LOW OVER THE
MID-ATLANTIC STATES AT THE END OF THE PERIOD GIVEN PLACEMENT OF
STRONGER HEIGHT FALLS FOCUSING STILL A TAD FARTHER SOUTH, WITH THE
UKMET ON THE SOUTHERN EDGE OF THE GUIDANCE SPREAD THROUGH
WEDNESDAY EVENING.
PAIR OF SHORTWAVE TROUGHS FOR THE NORTHWESTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/GFS/UKMET
CONFIDENCE: MODERATE
A MODEST AND RATHER PROGRESSIVE SHORTWAVE TROUGH FROM THE NORTH
PACIFIC IS EXPECTED TO CLIP WASHINGTON STATE AND REACH SOUTHERN
BRITISH COLUMBIA BY LATE TUESDAY. A WEAKENING COLD FRONT IS
EXPECTED TO ACCOMPANY THIS SHORTWAVE FEATURE AS IT HEADS INTO AN
UPPER LEVEL RIDGE AXIS, ALTHOUGH THE PARENT SURFACE LOW WILL PASS
WELL TO THE NORTH NEAR THE SOUTHEAST ALASKA PANHANDLE. IN TERMS
OF THE LATEST MODEL GUIDANCE, THERE IS NOW ENOUGH MODEL AGREEMENT
TO SUPPORT A GENERAL MODEL BLEND FOR THIS FIRST WAVE.
A SECOND SHORTWAVE DISTURBANCE WILL TRACK JUST BEHIND IT AND
SHOULD REACH THE PACIFIC NORTHWEST ON THURSDAY, WITH THE FRONT
MOVING INLAND ACROSS PORTIONS OF THE WEST, AND A BROADER SHORTWAVE
MOVES IN RIGHT BEHIND IT ACROSS NORTHERN CALIFORNIA. THE GUIDANCE
REFLECTS A RELATIVELY LOW-AMPLITUDE TO THIS SYSTEM AT LEAST
THROUGH THIS PERIOD, WITH THE NAM AND UKMET INITIALLY A LITTLE
STRONGER AS THE SYSTEM APPROACHES THE COAST, AND THE 00Z CMC IS
TOO WEAK WITH THE LAST SHORTWAVE MOVING IN ACROSS CALIFORNIA
COMPARED TO THE MODEL CONSENSUS. ALTHOUGH THE 00Z GFS IS SLIGHTLY
MORE AMPLIFIED ALOFT, IT IS IN BETTER AGREEMENT COMPARED TO
EARLIER RUNS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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