424
FXUS10 KWNH 170656
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 AM EST MON FEB 17 2020
VALID FEB 17/0000 UTC THRU FEB 20/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z FINAL 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/00Z 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 00Z CMC
TRENDED CLOSER TO THE MODEL CONSENSUS WITH THE DEPTH OF THE TROUGH
AND THE SURFACE LOW POSITION, ALTHOUGH STILL A LITTLE WEAKER
ALOFT. SIMILAR TO ITS 12Z RUN, THE 00Z UKMET REMAINS SLIGHTLY
SLOWER WITH THE PROGRESSION OF THE COLD FRONT BUT BETTER CLUSTERED
WITH THE LOW POSITION 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/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 GFS AND NAM ARE NOW AMONG THE MOST AMPLIFIED SOLUTIONS
WHEREAS THE NON-NCEP GUIDANCE IS A LITTLE WEAKER. THE PREFERENCE
REMAINS THE SAME EXCEPT TO SUBSTITUTE THE 00Z GEFS MEAN FOR THE
18Z RUN.
BROAD UPPER LEVEL TROUGH BUILDING ACROSS THE INTERMOUNTAIN WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z 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
AND NAM INDICATING THE GREATEST DEGREE OF UNDERCUTTING, AND THE
NAM IS ALSO STRONGER ACROSS THE NORTHERN ROCKIES AND GREAT BASIN
BY WEDNESDAY NIGHT.
LONGWAVE TROUGH APPROACHING THE WEST COAST BY THURSDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GEFS MEAN/00Z ECMWF/00Z CMC
CONFIDENCE: NEAR AVERAGE
THE UPPER LEVEL RIDGE HOLDS OVER THE WEST COAST REGION THROUGH
WEDNESDAY NIGHT, AFTER WHICH HEIGHT FALLS ENSUE AS THE NEXT STORM
SYSTEM APPROACHES FROM THE EASTERN PACIFIC. THIS WILL LIKELY BE
AN ELONGATED TROUGH AXIS WITH A HINT OF A CLOSED LOW DEVELOPING.
THE NAM APPEARS MORE AMPLIFIED THAN THE MODEL CONSENSUS, AND THE
UKMET SLIGHTLY SLOWER. THE 00Z GEFS MEAN APPEARS TO HAVE A GOOD
DEPICTION OF THE EVOLUTION, AND IS SUPPORTED BY THE CMC, ECMWF,
AND TO A LESSER DEGREE THE GFS.
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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