333
FXUS10 KWNH 281647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 PM EDT SUN JUN 28 2020
VALID JUN 28/1200 UTC THRU JUL 2/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLOSED LOW ANCHORED OVER NEW ENGLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
AN UPPER-LEVEL LOW INITIALLY OVER SOUTHERN QUEBEC IS FORECAST TO
REACH CENTRAL NEW ENGLAND BY MONDAY AND THEN BECOME ANCHORED IN
PLACE THROUGH THE MIDDLE OF THE WEEK AS IT BECOMES CUT OFF FROM
THE MAIN NORTHERN STREAM FLOW. THE MODELS HAVE TRENDED CLOSER TO
A TIGHT CONSENSUS REGARDING THIS LOW/TROUGH, WITH THE CMC ONLY
SLIGHTLY DISPLACED TO THE NORTHEAST WITH THE CORE OF THE UPPER
LOW. HOWEVER, THE DIFFERENCE IS SMALL ENOUGH TO MERIT A GENERAL
MODEL BLEND FOR THE NORTHEAST U.S.
DEEP UPPER TROUGH/CLOSED LOW ACROSS THE INTERMOUNTAIN WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET/ECMWF
CONFIDENCE: AVERAGE
A STRONG MID-UPPER LEVEL LOW CURRENTLY OVER THE PACIFIC NORTHWEST
IS FORECAST TO CONTINUE AMPLIFYING ACROSS THE NORTHERN ROCKIES AND
INTERMOUNTAIN WEST THROUGH TUESDAY MORNING AS AN UPPER-LEVEL RIDGE
BUILDS ACROSS THE MIDWEST AND GREAT LAKES REGION, AND THEN THE
CORE OF THE UPPER LOW SHOULD BE CENTERED OVER SOUTHWEST CANADA BY
WEDNESDAY. THIS WILL YIELD A QUASI OMEGA-BLOCK PATTERN ACROSS THE
NORTH-CENTRAL U.S. THROUGH THE MIDDLE OF THE WEEK. THE 12Z NAM
TENDS TO LIFT THE TROUGH OUT FASTER THAN THE OTHER GUIDANCE, AND
THEREFORE THE SURFACE LOW OVER ALBERTA IS DISPLACED TO THE NORTH.
THE 00Z CMC IS SLOWER WITH THE TROUGH EVOLUTION AND LAGS THE
REMAINING MODEL SUITE AS THE ENERGY PIVOTS THROUGH THE
INTERMOUNTAIN REGION, RESULTING IN A SOUTHEASTWARD DISPLACEMENT OF
THE MID-LEVEL LOW CENTER. THE 12Z GFS, 00Z UKMET AND 00Z ECMWF
HAVE SOME MODEST TIMING/DEPTH DIFFERENCES BUT OVERALL ARE WELL
CLUSTERED AND REPRESENT THE MODEL CONSENSUS, SO A BLEND OF THOSE
MODELS SHOULD WORK WELL.
SHORTWAVE LIFTING FROM THE WESTERN HIGH PLAINS TO THE UPPER MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z UKMET/ECMWF BLEND
CONFIDENCE: AVERAGE
AHEAD OF THE DEEP WESTERN U.S. TROUGH/CLOSED LOW WILL BE A
SHORTWAVE PERTURBATION THAT EJECTS NORTHEAST OUT ACROSS THE PLAINS
AND MIDWEST. THE SHORTWAVE THAT IS CURRENTLY OVER WESTERN KANSAS
IS FORECAST TO TRACK NORTHEASTWARD TO THE UPPER MIDWEST AND
AMPLIFY INTO POSSIBLY A WEAK CLOSED LOW OVER WESTERN ONTARIO AS
SUGGESTED BY THE 12Z NAM, AS SOME MODEST ENERGY LIFTING NORTHEAST
IN BEHIND IT MERGES AND CONSOLIDATES WITH IT, AND THERE HAS BEEN A
GRADUAL TREND TO A STRONGER SHORTWAVE IN THE GUIDANCE. THIS ALSO
HOLDS TRUE WITH THE 12Z GFS. GIVEN THE TREND TO A STRONGER
SOLUTION, A BLEND OF THE GFS/NAM/ECMWF SHOULD SUFFICE AS A
STARTING POINT.
SHORTWAVE CROSSING THE RIO GRANDE VALLEY ON SUNDAY
AMPLIFYING TOWARD MID MS VALLEY BY MONDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE
THE GUIDANCE SUPPORTS A CONVECTIVELY ENHANCED SHORTWAVE OR MCV
LIFTING NORTHEAST ACROSS THE LOWER/MIDDLE RIO GRANDE VALLEY ON
SUNDAY WHICH IS FORECAST TO LIFT NORTHEAST TOWARD THE MID-SOUTH BY
MONDAY NIGHT WHILE ATTEMPTING TO AMPLIFY. THE MODELS ALL APPEAR
TO BE TRENDING STRONGER WITH THIS FEATURE OVERALL, AND SUPPORT A
WEAK MID-LEVEL LOW CENTER IMPACTING THE GENERAL VICINITY OF
SOUTHERN ILLINOIS BY TUESDAY MORNING, WITH THIS FEATURE MOST
EVIDENT AT 700 MB. ONE OF THE MAIN DIFFERENCES NOTED WAS A
STRONGER CMC SOLUTION ACROSS THE OHIO VALLEY BY WEDNESDAY, WHEREAS
THE OTHER MODELS ARE SUGGESTING A SLIGHTLY WEAKER LOW THAT IS
FARTHER NORTH. FOR NOW, A NON-CMC BLEND IS 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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