272
FXUS10 KWNH 071846
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 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/ECMWF AND 12Z GEFS/00Z ECENS
CONFIDENCE: BELOW 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 ITSELF ACROSS THE OH VALLEY
AND MID-ATLANTIC IS RATHER SMALL, HOWEVER THE 12Z GFS IS A BIT OF
A STRONG OUTLIER WITH ITS INTENSITY COMPARED TO THE REMAINING
GUIDANCE. THE MODEL SPREAD WORSENS WITH RESPECT TO NEW ENGLAND AS
THE LOW TRACKS NORTHEASTWARD AND DEEPENS WITH TIME. THE 12Z NAM
ENDS UP FLATTER/WEAKER AND ON THE EAST SIDE OF THE MODEL SPREAD,
AND HAS AGREEMENT FROM THE 12Z UKMET, AND NOW THE 12Z CMC WHICH
TRENDED MUCH FARTHER EAST FROM ITS 00Z RUN. THE 12Z GFS AND 12Z
ECMWF ARE ON THE WEST SIDE OF THE MODEL SPREAD AND ARE DEEPER, BUT
THE ECMWF DID TREND A TAD EAST FROM ITS 00Z RUN. SO, THE GFS AND
ECMWF ARE STILL SUGGESTIVE OF STRONGER/QUICKER PHASING RELATIVE TO
THE NAM/UKMET/CMC CAMP WHICH ALLOWS THE LOW CENTER TO TUCK IN
CLOSER TO THE NEW ENGLAND COAST BEFORE EXITING UP ACROSS SOUTHEAST
CANADA. THE LATEST AVAILABLE ENSEMBLE MEANS DO NOT EXACTLY FOSTER
HIGH CONFIDENCE IN THIS FORECAST, AS THE 12Z CMCE MADE A STRONG
SHIFT FARTHER EAST AND IS WEAKER RELATIVE TO ITS 00Z SOLUTION. THE
12Z GEFS MEAN IS CURRENTLY A TAD EAST AND IS WEAKER IN COMPARISON
TO THE DETERMINISTIC GFS. THE LATEST ECENS MEAN (00Z CYCLE STILL)
IS VERY CLOSE TO THE CURRENT ECMWF. SO, AS A CONSENSUS, THERE IS
BIT MORE OF AN EASTWARD SHIFT IN THE GUIDANCE WITH THE LOW TRACK
RELATIVE TO NEW ENGLAND WHICH BEGAN GENERALLY WITH LAST NIGHT'S
00Z MODEL CYCLE AND HAS CONTINUED WITH TODAY'S 12Z CYCLE.
BASED ON THE LATEST TRENDS, ENSEMBLE MEANS AND CLUSTERING, A BLEND
OF THE 12Z GFS/ECMWF AND 12Z GEFS/00Z ECENS MEANS WILL BE
PREFERRED FOR THE SYSTEM, WHICH WILL TEMPER THE STRONGER GFS OVER
THE OH VALLEY AND MID-ATLANTIC WHILE ALSO PROMOTING AT LEAST A
MODEST EASTWARD SHIFT IN THE LOW TRACK RELATIVE TO NEW ENGLAND.
GIVEN THE RUN TO RUN VARIABILITY AND MODEL SPREAD, CONFIDENCE IS
BELOW AVERAGE.
...SHORTWAVES/SURFACE LOW IMPACTING THE NORTHERN PLAINS AND
MIDWEST THIS WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS, 12Z CMC AND 12Z 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 12Z 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, 12Z CMC AND 12Z ECMWF BLEND, AND
SO THIS CONSENSUS WILL BE PREFERRED.
..SHORTWAVE ENERGY CROSSING SOUTHERN CA BY SUN MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: 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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