070
FXUS10 KWNH 231644
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 PM EDT SAT MAY 23 2020
VALID MAY 23/1200 UTC THRU MAY 27/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CUT-OFF LOW EXITING THE NORTHEAST U.S. BY SATURDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
A WEAK UPPER LOW CURRENTLY SOUTH OF LONG ISLAND IS SUSTAINING A
SURFACE LOW THAT WILL EMERGE OFFSHORE TONIGHT AND THEN GRADUALLY
SLOW DOWN IN FORWARD MOTION BY SUNDAY AND INTO MONDAY, AS THE
UPPER LOW EVOLVES INTO AN OPEN WAVE. GIVEN THE NEAR-TERM
EVOLUTION AND TRACK OF THIS FEATURE, THERE IS ENOUGH MODEL
AGREEMENT TO MERIT THE USE OF A MULTI-DETERMINISTIC MODEL BLEND.
SOUTHERN STREAM TROUGH FROM INTERMOUNTAIN WEST TO SOUTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 48 HOURS, THEN 6Z GEFS
MEAN/00Z EC MEAN BLEND
CONFIDENCE: LIMITED-MODERATE
THE LATEST GUIDANCE SHOWS VERY GOOD AGREEMENT IN BRINGING A NEW
LARGE SCALE UPPER TROUGH AND ASSOCIATED CLOSED LOW IN ACROSS THE
INTERMOUNTAIN WEST THIS WEEKEND. BY MONDAY, THE MODELS SUPPORT A
DEEP TROUGH EDGING TOWARD THE PLAINS WITH ONE CLOSED LOW CENTER
EXITING THE NORTHERN ROCKIES AND CROSSING THE NORTHERN HIGH PLAINS
BY THEN. MEANWHILE, A SECOND CLOSED LOW WILL BE ATTEMPTING TO
FOCUS OVER THE CENTRAL ROCKIES, AND BY TUESDAY THE GUIDANCE IS IN
REASONABLY GOOD AGREEMENT ON THE IDEA OF THIS CLOSED LOW BECOMING
BETTER DEFINED OUT ACROSS THE SOUTHERN HIGH PLAINS. THIS WILL
RESULT IN A CORRESPONDING SURFACE LOW, AND WITH THIS FEATURE THERE
IS A FAIR DEGREE OF MODEL MASS FIELD SPREAD. THE 00Z CMC HAS A
WEAKER AND NORTHERLY TRACKING LOW CENTER UP OVER SOUTHWEST
MISSOURI AT THE END OF THE PERIOD VERSUS THE 00Z UKMET, WHICH IS
THE STRONGEST SOLUTION AND HAS IT DOWN OVER SOUTHWEST OKLAHOMA
OWING TO THE STRONGER RIDGE ACROSS THE EAST-CENTRAL U.S. COMPARED
TO THE OTHER GUIDANCE. A GENERAL MODEL BLEND SHOULD GENERALLY
SUFFICE WITH THIS ENTIRE MASS FIELD EVOLUTION THROUGH 48 HOURS,
BUT THEREAFTER AS THE DEEP TROUGH/CLOSED LOW EJECTS OUT ACROSS THE
PLAINS, A BLEND OF THE LATEST GEFS MEAN AND ECENS MEAN WILL BE
PREFERRED AS A STARTING POINT IN THE FORECAST PROCESS GIVEN THE
LARGE SPREAD IN THE DETAILS OF SURFACE CYCLOGENESIS.
SHORTWAVE/CLOSED LOW CROSSING THE MIDWEST THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z MONDAY, THEN NON-UKMET
BLEND
CONFIDENCE: MODERATE-HIGH
A RATHER COMPACT MID-UPPER LEVEL LOW HAS BEEN TRACKING ACROSS THE
CENTRAL PLAINS AND IS NOW OVER IOWA. THIS LOW WILL BE ADVANCING
NORTHEAST ACROSS MINNESOTA AND WISCONSIN THROUGH SATURDAY NIGHT,
AND THEN GRADUALLY WEAKENING OVER THE NORTHERN GREAT LAKES ON
SUNDAY AS IT TRACKS AROUND THE NORTHERN PERIPHERY OF THE BUILDING
SOUTHEAST U.S. UPPER RIDGE. THE MODEL GUIDANCE IS IN GOOD
AGREEMENT OVERALL WITH THIS SYSTEM THROUGH 12Z MONDAY, AFTER WHICH
THE 00Z UKMET DEPICTS A SOMEWHAT STRONGER TROUGH THAT EXITS THE
GREAT LAKES AND MOVES ACROSS NORTHERN NEW ENGLAND FOR EARLY IN THE
WEEK. GIVEN GOOD CLUSTERING IN THE GUIDANCE OTHERWISE, A
NON-UKMET BLEND WILL BE PREFERRED FOR THIS REGION.
SHORTWAVE LIFTING NORTHEAST ACROSS THE SOUTHERN PLAINS ON SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE
AS THE DEEP TROUGH AND ASSOCIATED CLOSED LOW EVOLVES ACROSS THE
WEST THIS WEEKEND AND SLOWLY ENCROACHES ON THE HIGH PLAINS, THERE
WILL BE A WEAK SHORTWAVE TROUGH PIVOTING AROUND THE BASE OF THAT
AND LIFTING NORTHEAST ACROSS TEXAS THROUGH SUNDAY NIGHT, AND THIS
IS EXPECTED TO SUPPORT THE DEVELOPMENT OF AN MCS ACROSS PORTIONS
OF SOUTHERN TEXAS. BASED ON THE LATEST TRENDS AND DETERMINISTIC
CLUSTERING, A GENERAL MODEL BLEND WILL BE PREFERRED.
MID-LEVEL TROUGH IMPACTING FLORIDA EARLY IN THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/NAM/00Z EC MEAN
CONFIDENCE: MODERATE
AS A STRONG SUBTROPICAL RIDGE BUILDS OVER THE SOUTHEAST AND THE
MID-ATLANTIC REGION GOING INTO THE BEGINNING OF THE WEEK, THERE
WILL BE A MID-LEVEL TROUGH AXIS LIFTING NORTH FROM THE YUCATAN
PENINSULA AND WESTERN CARIBBEAN SEA TO THE SOUTHERN GULF OF
MEXICO. THIS ENERGY IS EXPECTED TO ELONGATE AND CROSS AREAS OF
SOUTHERN FLORIDA BY LATE MONDAY AND INTO TUESDAY. THERE WILL
LIKELY BE AN INVERTED SURFACE TROUGH THAT ACCOMPANIES THIS AS
WELL. THE UKMET IS STRONGER WITH THE BUILDING RIDGE TO THE NORTH
AND LOSES ENSEMBLE SUPPORT, AND THERE HAS BEEN A MULTI-MODEL TREND
TO FOCUS A STRONGER MID-LEVEL TROUGH A BIT FARTHER NORTH OVER THE
SOUTHEAST GULF OF MEXICO AND SOUTHERN FLORIDA FOR MONDAY AND
TUESDAY. THE 00Z ECMWF APPEARS MUCH HEAVIER WITH THE QPF ACROSS
THE REGION COMPARED TO THE OTHER GUIDANCE, OWING LARGELY TO HIGHER
INSTABILITY OVER LAND WITH ITS SOLUTION. TAKING THESE FACTORS
INTO ACCOUNT, THE PREFERENCE AT THIS TIME WILL BE FOR A BLEND OF
THE 12Z GFS/NAM/00Z EC MEAN.
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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