724
FXUS10 KWNH 160636
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 AM EDT SAT MAY 16 2020
VALID MAY 16/0000 UTC THRU MAY 19/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
07Z UPDATE: NO SIGNIFICANT CHANGES WITH THE REST OF THE 00Z
GUIDANCE NOW AVAILABLE. FOR THE POTENTIAL LOW PRESSURE DEVELOPMENT
OFF THE FL COAST AND EVENTUAL TRACK UP THE EAST COAST, THE GFS
CONTINUES TO BE THE WESTERN OUTLIER, THOUGH THERE HAS BEEN A
GRADUAL TREND IN THE GUIDANCE TO THE WEST. FOR NOW, WILL CONTINUE
TO PREFER A NON-GFS BLEND AFTER 60 HOURS /18.12Z/. ELSEWHERE, THE
REST OF THE GUIDANCE HASN'T CHANGED MUCH TO DEVIATE FROM THE
ONGOING BLEND PREFERENCES.
SHORTWAVE AND SURFACE LOW TRACKING ACROSS THE NORTHERN TIER STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z ECMWF, AND 12Z ECENS BLEND
CONFIDENCE: AVERAGE
SHORTWAVE ENERGY SKIRTING THROUGH THE NORTHERN ROCKIES IS EXPECTED
TO AMPLIFY AND DEEPEN AS IT MOVES TOWARD THE UPPER MISSISSIPPI
RIVER VALLEY BY SUNDAY, WITH THE SHORTWAVE ENERGY TAKING ON A MORE
NEGATIVE TILT. IN THE INCREASING AMPLIFIED PATTERN OVER THE CONUS
(THANKS TO A DIGGING LONGWAVE TROUGH OVER THE WESTERN US AND
BUILDING HEIGHTS OVER THE CENTRAL PLAINS), THE SHORTWAVE IS
FORECAST TO EXPAND AND CLOSE OFF OVER THE LOWER GREAT LAKES AND
OHIO VALLEY EARLY NEXT WEEK. THIS SETUP OFFERS AVERAGE AT BEST
FORECAST CONFIDENCE BUT THE OBVIOUS OUTLIERS AT THIS POINT APPEAR
TO BE THE 12Z CMC AND 12Z UKMET WHICH ARE OPEN/FASTER COMPARED TO
THE MORE CLOSED OFF NAM/GFS AND ECMWF SOLUTIONS. THE TREND OVER
THE LAST FEW DAYS HAS BEEN FOR THE CUT-OFF LOW TO REMAIN
STATIONARY OR SLOWLY WOBBLE IN THE AREA. THE 00Z NAM HOWEVER
APPEARS TO BE OVERDONE AND TOO DEEP WITH THE LOW BY 72-84 HOURS.
AS SUCH, THE PREFERRED BLEND IS FOR A COMPROMISE OF THE 00Z GFS
AND 12Z ECMWF WITH SOME INCORPORATION OF THE 12Z ECENS MEAN.
DEEP UPPER LEVEL TROUGH DEVELOPING ALONG THE WEST COAST BY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A LARGE CLOSED MID/UPPER LEVEL LOW IS FORECAST TO MOVE FROM THE
EASTERN PACIFIC TOWARD THE PACIFIC NORTHWEST COAST THROUGH THE
PERIOD. GIVEN THE HIGHLY AMPLIFIED PATTERN, THE MODEL GUIDANCE
SHOWS ABOVE AVERAGE AGREEMENT, WITH ONLY SOME MINOR DIFFERENCES AT
500 MB ON DAY 3 NOTED. AS THE SYSTEM APPROACHES THE COAST LATE ON
DAY 2 AND INTO DAY 3, IT WILL STALL AND THE SURFACE LOW WEAKENS.
MODEL AGREEMENT IS ABOVE AVERAGE IN THIS SETUP AND A GENERAL MODEL
BLEND SHOULD SUFFICE.
SOUTHERN STREAM TROUGH TRACKING FROM TEXAS AND ALONG THE GULF COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A SUBTLE/WEAK SOUTHERN STREAM SHORTWAVE WILL MOVE ACROSS SOUTHERN
PLAINS THROUGH THIS WEEKEND WITH THE MID-LEVEL WAVE DAMPENING OUT
OVER THE NORTHERN GULF BY EARLY NEXT WEEK. MODEL GUIDANCE SHOWS
AVERAGE TO SLIGHTLY ABOVE AVERAGE AGREEMENT WITH JUST MINOR TIMING
DIFFERENCES NOTED IN THE 500 MB PATTERN. THE CMC WAS A SLOW
OUTLIER WHILE THE GFS WAS ON THE FASTER SIDE OF THE MODEL SPREAD.
BUT THESE DIFFERENCES APPEAR TO BE FAIRLY MINOR AND A GENERAL
MODEL BLEND IS FAVORED AT THIS POINT.
A RELATIVELY WEAK SOUTHERN STREAM TROUGH WILL MOVE ACROSS THE
SOUTHERN PLAINS THROUGH EARLY SATURDAY, AND GRADUALLY THE MID
LEVEL LOW CROSSES THE GULF COAST STATES BY LATE IN THE WEEKEND.
THE 12Z NAM IS A LITTLE FARTHER NORTH WITH THE 700MB LOW ACROSS
TEXAS, AND THIS RESULTS IN LESS QPF COMPARED TO THE OTHER MODELS
THROUGH SATURDAY EVENING. THE UKMET IS NOTED AS A SLOWER SOLUTION
BY MONDAY, AND THEREFORE HEAVIER QPF ACROSS THE CENTRAL GULF COAST
REGION. A BLEND OF THE ECMWF/GFS WOULD SERVE AS A GOOD STARTING
POINT SINCE THERE IS DECENT ENSEMBLE SUPPORT FOR THIS INITIAL
BLEND.
LOW PRESSURE DEVELOPING NEAR THE BAHAMAS...MOVING UP THE SOUTHEAST
COAST THROUGH EARLY NEXT WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 60 HOURS /18.12Z/ THEN
NON-GFS
CONFIDENCE: AVERAGE
AN AREA OF LOW PRESSURE OFF THE SOUTHEAST FLORIDA COAST IS
EXPECTED TO GRADUALLY FURTHER DEVELOP THIS WEEKEND AND THEN TURN
NORTHWARD THIS WEEKEND BEFORE TRACKING OFF THE NC COAST BY EARLY
NEXT WEEK. MODEL AGREEMENT HAS COME INTO BETTER FOCUS THROUGH 60
HOURS, WITH A REASONABLE SPREAD BETWEEN THE VARIOUS DETERMINISTIC
GUIDANCE. THE LATEST /00Z/ GFS OFFERS A SOLUTION WEST OF ITS 18Z
ENSEMBLE MEAN AND IS ALSO ON THE WESTERN SIDE OF THE MODEL SPREAD
ENVELOPE. THE 12Z ECMWF IS ON THE EASTERN SIDE OF THE SPREAD WITH
THE NAM/UKMET/CMC IN THE MIDDLE. GIVEN THE OUTLIER WESTERN
SOLUTION THE GFS IS ADVERTISING AT THIS POINT AND WITHOUT THE
ENSEMBLE SUPPORT, A NON-GFS BLEND AFTER 18.12Z IS PREFERRED. FOR
MORE INFORMATION ON THIS SYSTEM AND POTENTIAL DEVELOPMENT, SEE THE
LATEST FROM THE NATIONAL HURRICANE CENTER.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
TAYLOR
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