664
FXUS10 KWNH 080446
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 AM EDT FRI MAY 08 2020
VALID MAY 08/0000 UTC THRU MAY 11/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z 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 08/00Z GFS AND THE 07/12 ECMWF AND 12Z
GEFS
CONFIDENCE: BELOW AVERAGE
DURING THE DAY TODAY, FRIDAY, SHORTWAVE 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 THIS 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 08/00Z GFS WAS A BIT
OF A STRONG OUTLIER WITH ITS INTENSITY COMPARED TO THE REMAINING
GUIDANCE DESPITE THE FACT THAT THE 00Z RUN OF THE GFS TEMPERED THE
DEPTH OF THE LOW A BIT COMPARED WITH PREVIOUS RUNS. THE MODEL
SPREAD WORSENS WITH RESPECT TO NEW ENGLAND AS THE LOW TRACKS
NORTHEASTWARD AND DEEPENS WITH TIME. THE 08/00Z NAM WAS STILL ENDS
UP FLATTER/WEAKER AND ON THE EAST SIDE OF THE MODEL SPREAD, AND
HAS AGREEMENT FROM THE 07/12Z UKMET. 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.
BASED ON THE LATEST TRENDS, ENSEMBLE MEANS AND CLUSTERING, A BLEND
OF THE 08/00Z GFS AND 07/12Z ECMWF AND THEIR RESPECTING MEANS
REMAIN PREFERRED FOR THE SYSTEM BECAUSE THAT BLEND TEMPERS 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 08/00Z GFS, 07/12Z CMC AND ECMWF
CONFIDENCE: AVERAGE
DOWNSTREAM OF A SHARP AND ELONGATED MID-LEVEL RIDGE IN PLACE OVER
WESTERN NORTH AMERICA TODAY THROUGH 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 08/00Z GFS TENDED TO BE STRONGER AND FASTER THAN
OTHER GLOBAL GUIDANCE AND THE LATEST NAM. OF THE GLOBAL MODELS,
THE 07/12Z UKMET REMAINED 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.
..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 REMAINS THE PREFERRED OPTION.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
BANN
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