259
FXUS10 KWNH 071633
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1232 PM EDT THU MAY 07 2020
VALID MAY 07/1200 UTC THRU MAY 11/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...ENERGY DIGGING SOUTHEAST FROM THE NORTHERN PLAINS TO THE OH
VALLEY AND MID-ATLANTIC...
..STRONG VORTEX OVER SOUTHEAST CANADA AND THE NORTHEAST
..DEEPENING SURFACE LOW FROM THE OH VALLEY TO THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE
A COMPACT MID-LEVEL CLOSED LOW AND ASSOCIATED TROUGH OVER THE
NORTHERN HIGH PLAINS THIS MORNING WILL DIG SOUTHEAST ACROSS THE
MIDWEST THROUGH THURSDAY. BY FRIDAY, THE ENERGY WILL BE CROSSING
THE OH VALLEY AND WILL BE ATTEMPTING TO PHASE WITH VERY STRONG
NORTHERN STREAM HEIGHT FALLS/TROUGHING ASSOCIATED WITH A VORTEX
SETTLING SOUTH OVER EASTERN ONTARIO AND SOUTHWEST QUEBEC. THIS
WILL LEAD TO STRENGTHENING LOW PRESSURE UP ACROSS THE OH VALLEY
ALONG A FRONTAL BOUNDARY, AND THIS LOW CENTER WILL THEN CROSS THE
MID-ATLANTIC BY FRIDAY EVENING. ON SATURDAY, THE COUPLING/PHASED
RESULTANT OF ENERGY MOVING INTO THE NORTHEAST WILL YIELD A HIGHLY
ANOMALOUS CLOSED LOW AND ASSOCIATED UPPER TROUGH OVER THE
NORTHEAST U.S. (500 MB HEIGHTS 3 TO 4 STANDARD DEVIATIONS BELOW
NORMAL), WITH LIKELIHOOD OF A RAPIDLY DEEPENING SURFACE LOW
LIFTING UP ACROSS OR JUST OFFSHORE OF COASTAL NEW ENGLAND.
THE MODEL SPREAD WITH THE LOW TRACK ACROSS THE OH VALLEY AND
MID-ATLANTIC IS RATHER SMALL, WITH THE DIFFERENCES HERE MAINLY
RELATED TO THE 12Z GFS BEING A BIT STRONGER THAN THE MODEL
CONSENSUS. HOWEVER, THE DIFFERENCES INCREASE MARKEDLY WITH RESPECT
TO NEW ENGLAND AS THE LOW TRACKS NORTHEASTWARD AND DEEPENS WITH
TIME. THE 12Z NAM ENDS UP FARTHER EAST, FLATTER AND WEAKER THAN
THE GLOBAL MODEL SUITE, WITH EXCEPTION TO THE 00Z UKMET WHICH IS
ALSO WEAKER AND FLATTER. THE 12Z GFS, 00Z CMC AND 00Z ECMWF ARE
ALL DEEPER AND FARTHER WEST WITH THE LOW TRACK, AND SUGGESTIVE OF
STRONGER/QUICKER PHASING RELATIVE TO THE NAM/UKMET CAMP WHICH
ALLOWS THE LOW CENTER TO TUCK IN CLOSER TO THE NEW ENGLAND COAST
AND EVEN SLIGHTLY INLAND BEFORE EXITING UP ACROSS SOUTHEAST
CANADA. THE 06Z GEFS/00Z ECENS AND 00Z CMCE ALL SUPPORT A
GFS/ECMWF WEIGHTED SOLUTION, WITH THE IDEA THAT THE NAM AND UKMET
ARE A BIT TOO WEAK/FLAT AND TOO FAR EAST, AND WITH A LIKELIHOOD
THAT THE DETERMINISTIC CMC (AT LEAST FROM 00Z) IS OVERALL TOO FAR
WEST. SO, WILL PREFER A BLEND OF THE 12Z GFS AND 00Z ECMWF FOR THE
TIME BEING.
...SHORTWAVES/SURFACE LOW IMPACTING THE NORTHERN PLAINS AND
MIDWEST THIS WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS, 00Z CMC AND 00Z ECMWF
CONFIDENCE: AVERAGE
DOWNSTREAM OF A SHARP AND ELONGATED MID-LEVEL RIDGE IN PLACE OVER
WESTERN NORTH AMERICA ON FRIDAY AND SATURDAY, AND EMBEDDED WITHIN
DEEP LAYER NORTH-NORTHWEST FLOW OVER CENTRAL CANADA, A PAIR OF
SHORTWAVES WILL DROP DOWN OUT OF CANADA AND DOWN ACROSS PORTIONS
OF THE NORTHERN PLAINS AND MIDWEST THIS WEEKEND. THE LEAD
SHORTWAVE WILL HAVE A LOW CENTER AND COLD FRONT ASSOCIATED WITH IT
WHICH WILL CROSS THE DAKOTAS ON SATURDAY AND THEN GRADUALLY WEAKEN
AS IT CROSSES THE MIDWEST ON SUNDAY. MODEL SPREAD IS RELATIVELY
MINIMAL, BUT THE 12Z NAM IS GENERALLY A TAD STRONGER WITH THE
SHORTWAVE ENERGY AND ALSO THE SURFACE LOW REFLECTION COMPARED TO
THE GLOBAL MODELS. THE NAM IS ALSO A TAD FASTER WITH THE SURFACE
LOW EVOLUTION. OF THE GLOBAL MODELS, THE 00Z UKMET IS THE MOST
QUESTIONABLE AT THIS TIME AS IT HAS A SLOWER SHORTWAVE EVOLUTION
AND SURFACE REFLECTION RELATIVE TO THE MODEL CONSENSUS AND THE
ENSEMBLE MEANS. THE BEST OVERALL MODEL CLUSTERING AND ENSEMBLE
SUPPORT TENDS TO FAVOR A 12Z GFS, 00Z CMC AND 00Z ECMWF BLEND, AND
SO THIS CONSENSUS WILL BE PREFERRED.
..SHORTWAVE ENERGY CROSSING SOUTHERN CA BY SUN MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW A WEAK SHORTWAVE CROSSING AREAS OF COASTAL
SOUTHERN CA AND THEN THE DESERT SOUTHWEST ON SUNDAY. GIVEN THE
MODEST SPREAD IN TIMING AND DEPTH RELATING TO THIS ENERGY, A
GENERAL MODEL BLEND WILL STILL 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
ORRISON
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