287
FXUS10 KWNH 170430
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1130 PM EST SUN FEB 16 2020
VALID FEB 17/0000 UTC THRU FEB 20/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z INITIAL MODEL EVALUATION WITH PREFERENCES & CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
UPPER TROUGH CROSSING THE NORTHEAST ON MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
BROAD CYCLONIC FLOW ALOFT OVER THE NORTH-CENTRAL U.S. WILL SUPPORT
THE PASSAGE OF A FEW SHORTWAVE PERTURBATIONS THROUGH THE BEGINNING
OF THE WORK WEEK. THE LEAD IMPULSE WILL TRACK EASTWARD ACROSS THE
NORTHEAST ON MONDAY, WITH AN ATTENDANT COLD FRONT CROSSING NEW
ENGLAND BY MONDAY NIGHT. THERE IS ENOUGH MASS FIELD AGREEMENT IN
THE MODELS TO MERIT A GENERAL MODEL BLEND FOR THIS FEATURE.
SHORTWAVE IMPULSE AND SURFACE LOW ACROSS UPPER MIDWEST MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
BY MONDAY EVENING THE UPPER LEVEL FLOW PATTERN IS EXPECTED TO
BECOME MORE SEPARATED WITH A NORTHERN AND SOUTHERN STREAM
COMPONENT. TWO SEPARATE SHORTWAVES IN QUICK SUCCESSION ARE
PROGGED TO CROSS THE UPPER MIDWEST AND NORTHERN GREAT LAKES
REGION, WITH THE FIRST ONE TRACKING EASTWARD ACROSS THE UPPER
MIDWEST AND THE DAKOTAS ON MONDAY, AND THEN REACHING THE NORTHERN
GREAT LAKES BY EARLY TUESDAY. THIS WILL SUPPORT A WAVE OF LOW
PRESSURE ALONG A COLD FRONT ACROSS THIS REGION. THE MAIN
DIFFERENCE IN THE MODELS IS WITH THE 12Z CMC, INDICATING A FLATTER
TROUGH AND A SUPPRESSED SURFACE LOW ACROSS THE GREAT LAKES REGION.
THE 12Z UKMET IS SLIGHTLY SLOWER WITH THE PROGRESSION OF THE COLD
FRONT AND FARTHER NORTH WITH THE LOW OVER THE GREAT LAKES REGION.
THERE IS ENOUGH AGREEMENT AMONG THE GFS AND ECMWF TO MERIT A BLEND
OF THOSE TWO MODELS AS A STARTING POINT IN THE FORECAST.
SECOND SHORTWAVE IMPULSE REACHING THE GREAT LAKES TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS/18Z GEFS MEAN
CONFIDENCE: NEAR AVERAGE
A MID LEVEL IMPULSE WILL QUICKLY FOLLOW IN PROGRESSIVE NORTHWEST
FLOW OVER NORTHERN MINNESOTA AND NORTHERN MICHIGAN ON TUESDAY, AND
EVENTUALLY CONSOLIDATE WITH THE PREVIOUS SHORTWAVE MENTIONED
ABOVE. THE MAIN DIFFERENCE IN THE MODELS IS THE 12Z UKMET IS
SLOWER AND THE CMC IS WEAKER. THERE IS VERY GOOD AGREEMENT AMONG
THE 00Z NAM, GFS, AND 18Z GEFS MEAN TO WARRANT A BLEND OF THESE
MODELS TO START WITH.
BROAD UPPER LEVEL TROUGH BUILDING ACROSS THE INTERMOUNTAIN WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z EC MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE SOUTHERN STREAM COMPONENT OF THE UPPER LEVEL FLOW IS FORECAST
TO EVOLVE INTO A BROAD TROUGH OVER THE INTERMOUNTAIN WEST BY
MONDAY NIGHT WHILST AN UPPER LEVEL RIDGE AXIS BUILDS JUST WEST OF
THE WEST COAST. SOME OF THE SHORTWAVE ENERGY MAY TRY TO UNDERCUT
THE RIDGE AND FORM A TEMPORARY BLOCKING PATTERN. MOST OF THE
MODEL DIFFERENCES BECOME APPARENT AFTER 60 HOURS, WITH THE UKMET
INDICATING THE GREATEST DEGREE OF UNDERCUTTING, AND THE NAM IS
STRONGER ACROSS THE NORTHERN ROCKIES AND GREAT BASIN BY DAY 3.
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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