022
FXUS10 KWNH 111852
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT SAT APR 11 2020
VALID APR 11/1200 UTC THRU APR 15/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SOUTHERN STREAM SHORTWAVE LEADING TO INTENSE SURFACE LOW OVER
GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/UKMET
CONFIDENCE: MODERATE
THE CLOSED SOUTHERN STREAM LOW CURRENTLY OVER THE DESERT SOUTHWEST
WILL GRADUALLY TRACK EASTWARD ACROSS THE SOUTHERN ROCKIES THROUGH
TONIGHT, AND THEN INTO A PROGRESSIVE AND POTENT SHORTWAVE ACROSS
THE SOUTHERN PLAINS THROUGH SUNDAY. THIS SHORTWAVE BEGINS PHASING
WITH A NORTHERN STREAM TROUGH BY MONDAY MORNING AND ACQUIRING
NEGATIVE TILT IN THE PROCESS. THIS CONSOLIDATION WITH A STRONG
NORTHERN STREAM TROUGH AMPLIFYING OVER THE UPPER MIDWEST THROUGH
MONDAY WILL LEAD THE WAY FOR A RAPIDLY INTENSIFYING SURFACE LOW TO
LIFT NORTHEASTWARD ACROSS THE OHIO VALLEY AND GREAT LAKES, ALONG
WITH A STRONG COLD FRONT REACHING THE EAST COAST BY MONDAY
EVENING. IT APPEARS LIKELY THAT A DUAL SURFACE LOW STRUCTURE
DEVELOPS, AND THEN EVOLVES INTO ONE MAIN POWERFUL AND OCCLUDED LOW
BY MONDAY AFTERNOON ACROSS THE NORTHERN GREAT LAKES.
THE MOST RECENT GUIDANCE CONTINUES TO GRADUALLY CONSOLIDATE ON A
SOLUTION FOR THE DEPTH AND TRACK OF THE SURFACE LOW AS IT MOVES
FROM THE LOWER MISSISSIPPI VALLEY TO MICHIGAN. THE 12Z GEFS MEAN
TRENDED CLOSER TO THE MODEL CONSENSUS COMPARED TO ITS 6Z RUN,
WHICH WAS ON THE SLOWER SIDE OF THE GUIDANCE IN LIFTING THE LOW
NORTHWARD, AND THE 12Z GFS IS A BIT FASTER AND A LITTLE TO THE
SOUTHEAST OF THE ECMWF/CMC CLUSTER THAN IS CURRENTLY FARTHER
NORTHWEST WITH THE DEFORMATION ZONE. THE 00Z CMC IS WEAKER WITH
THE SHORTWAVE TROUGH AND THUS NOT QUITE AS STRONG WITH THE SURFACE
LOW CROSSING THE GREAT LAKES REGION AND THEN ONTARIO, AND THE 12Z
CMC DID NOT CHANGE THAT MUCH. THE 12Z UKMET IS SLIGHTLY SLOWER
WITH THE COLD FRONT REACHING THE EAST COAST, BUT CLOSE ENOUGH TO
BE PART OF THE MODEL BLEND. THE 12Z ECMWF TRENDED SLIGHTLY TO THE
SOUTHEAST WITH THE PARENT SURFACE LOW COMPARED TO ITS EARLIER RUN.
TO MITIGATE SOME OF THESE DIFFERENCES, A BLEND OF THE
GFS/ECMWF/UKMET IS PREFERRED FOR NOW AS A STARTING POINT IN THE
FORECAST PROCESS.
AMPLIFYING UPPER TROUGH OVER THE NORTHERN U.S. FOR EARLY IN THE
WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z CMC/12Z NAM
CONFIDENCE: MODERATE-HIGH
THE MODELS BRING AMPLIFYING SHORTWAVE/JET ENERGY SOUTHEASTWARD
FROM SOUTHWEST CANADA AND OUT ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS BY MONDAY, REINFORCING THE LONGWAVE PATTERN AND
BROAD CYCLONIC FLOW ALOFT OVER MUCH OF THE CONTINENTAL U.S. FOR
EARLY IN THE WEEK. OVERALL, THE MODELS ARE IN GOOD AGREEMENT WITH
THE DETAILS OF THE LONGWAVE TROUGH EVOLUTION, WITH THE EXCEPTIONS
OF THE 00/12Z UKMET THAT IS A BIT MORE AMPLIFIED AND THE 12Z GFS
THAT REMAINS ON THE PROGRESSIVE SIDE OF THE 12Z MODEL SUITE.
THEREFORE A BLEND OF THE 12Z ECMWF/12Z CMC/12Z NAM WILL BE
PREFERRED.
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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