258
FXUS10 KWNH 231822
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
222 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 FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
UPPER 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 12Z MONDAY, THEN 12Z 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 12Z CMC HAS A
WEAKER AND NORTHERLY TRACKING LOW CENTER UP OVER EASTERN KANSAS BY
TUESDAY MORNING AND HAS SOME SUPPORT FROM THE 12Z GFS. IN
CONTRAST, THE 12Z UKMET REMAINS SLIGHTLY STRONGER WITH THE LOW AND
FARTHER SOUTH OVER SOUTH-CENTRAL OKLAHOMA, OWING TO THE STRONGER
RIDGE ACROSS THE EAST-CENTRAL U.S. COMPARED TO THE OTHER GUIDANCE,
ALTHOUGH NOT TO THE SAME DEGREE AS THE 00Z UKMET. THE NAM IS
WEAKER AND EVEN MORE SUPPRESSED OVER TEXAS. A GENERAL MODEL BLEND
SHOULD GENERALLY SUFFICE WITH OVERALL EVOLUTION THROUGH 12Z
MONDAY, BUT THEREAFTER AS THE SYNOPTIC SCALE TROUGH 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
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, AND THE 12Z UKMET IS NOW CLOSE
ENOUGH TO THE OTHER DETERMINISTIC GUIDANCE COMPARED TO ITS 00Z
RUN, WHICH WAS A LITTLE BIT STRONGER. HAVING SAID THAT, A GENERAL
MODEL BLEND WILL WORK FOR THIS SHORTWAVE DISTURBANCE.
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 REACHES 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 OVERALL
DETERMINISTIC MODEL AGREEMENT, A GENERAL MODEL BLEND WILL BE
PREFERRED AS A STARTING POINT.
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 REMAINS 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. THE 12Z ECMWF IS
STILL HEAVIER THAN THE OTHER GUIDANCE WITH QPF, ALBEIT SLIGHTLY
LESS THAN ITS EARLIER RUN. TAKING THESE FACTORS INTO ACCOUNT, THE
PREFERENCE AT THIS TIME WILL CONTINUE TO 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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