109
FXUS10 KWNH 120450
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 AM EDT TUE MAY 12 2020
VALID MAY 12/0000 UTC THRU MAY 15/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-LEVEL TROUGH AMPLIFYING ACROSS THE NORTHEAST WITH
ACCOMPANYING SURFACE LOW THROUGH TUESDAY MORNING...
...SHORTWAVE MOVING ACROSS THE GREAT LAKES AND NORTHEAST TUESDAY
AND WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
MODELS SHOW OVERALL GOOD AGREEMENT WITH THE LEAD UPPER LEVEL
SHORTWAVE AND ASSOCIATED SURFACE LOW LIFTING ALONG THE NORTHERN
NEW ENGLAND COAST INTO THE CANADIAN MARITIMES TUESDAY MORNING.
THROUGH LATE TUESDAY, THERE IS ALSO GENERALLY GOOD AGREEMENT WITH
A SECOND SHORTWAVE FORECAST TO MOVE FROM THE GREAT LAKES INTO THE
NORTHEAST TUESDAY AND WEDNESDAY. BY EARLY WEDNESDAY AS THE SYSTEM
BEGINS TO MOVE EAST THROUGH THE GULF OF MAINE, MODELS BEGIN TO
SHOW MINOR TIMING DIFFERENCES - WITH THE 00Z NAM, 12Z UKMET AND
12Z CMC SLOWER THAN THE 00Z GFS, 12Z ECMWF AND THEIR ENSEMBLE
MEANS.
...UPPER TROUGH/CLOSED LOW ALONG THE NORTHWEST COAST THROUGH
WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS ARE IN FAIR AGREEMENT WITH THE MEAN CLOSED MID-LEVEL
LOW POSITION AS IT MEANDERS ALONG THE PACIFIC NORTHWEST COAST
THROUGH EARLY THURSDAY, AND THEN AS THE LOW WEAKENS AND MOVES
INLAND, UNDERCUTTING THE RIDGE CENTERED OVER BRITISH COLUMBIA
THURSDAY INTO EARLY FRIDAY.
...UPPER LOW CLOSING OFF OVER WESTERN CANADA ON TUESDAY BEFORE
MOVING EAST THROUGH THE CANADIAN PRAIRIE WEDNESDAY-THURSDAY...
...SURFACE CYCLONE MOVING TROUGH THE NORTH-CENTRAL U.S. WEDNESDAY
NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF AND EC ENSEMBLE MEAN
CONFIDENCE: BELOW AVERAGE
A COMBINATION OF SHORTWAVES WILL IMPACT THE NORTH-CENTRAL U.S.
FROM WEDNESDAY INTO THURSDAY. THE FIRST WILL BE RELATIVELY WEAK,
EMANATING FROM ID/MT/WY TUESDAY NIGHT AND REACHING EASTERN MONTANA
AND THE DAKOTAS ON WEDNESDAY. OVERALL, MODELS ARE FAIRLY GOOD
AGREEMENT WITH THIS FEATURE.
THIS LEADING WAVE IS FORECAST TO LIFT OUT AHEAD OF AN UPPER THAT
IS FORECAST TO DEVELOP AND DROP SOUTH ALONG THE EASTERN FRONT OF
THE CANADIAN ROCKIES TUESDAY INTO WEDNESDAY. OVERALL, MODELS ARE
IN GOOD AGREEMENT THROUGH EARLY WEDNESDAY AS THE SYSTEM DROPS INTO
SOUTHERN ALBERTA AND SASKATCHEWAN. HOWEVER, SIGNIFICANT TIMING
DIFFERENCES EMERGE AS THE UPPER SYSTEM AND ASSOCIATED LOW BEGIN TO
MOVE EAST THROUGH THE CANADIAN PRAIRIE WEDNESDAY NIGHT AND
THURSDAY. AT THE TWO EXTREMES ARE THE 00Z GFS - WHICH IS SLOWER
THAN MOST OF THE GUIDANCE BY WEDNESDAY NIGHT - AND THE 12Z UKMET
WHICH IS MUCH WEAKER AND SHOWS A MORE PROGRESSIVE PATTERN THAN THE
OTHER MODELS. BETWEEN THE TWO EXTREMES ARE THE 00Z NAM AND THE
12Z CANADIAN, ECMWF AND THE EC ENSEMBLE MEAN. ALTHOUGH THEY END
THE PERIOD IN GENERALLY GOOD AGREEMENT, WITH AN UPPER TROUGH
POSITION CENTERED OVER THE UPPER GREAT LAKES FRIDAY MORNING, THE
12Z ECMWF IS GENERALLY THE FASTEST OF THE FOUR - SUGGESTING THE
12Z ECMWF MAY BE A LITTLE TOO FAST WELL.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
PEREIRA
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