577
FXUS10 KWNH 211835
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT THU MAY 21 2020
VALID MAY 21/1200 UTC THRU MAY 25/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CUT-OFF LOW OVER LOWER OH AND TN RIVER VALLEYS, EXITING
MID-ATLANTIC LATE SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: NO SIGNIFICANT CHANGE WAS NOTED WITH THE 12Z UKMET,
CMC, ECMWF OR GEFS TO BREAK FROM INITIAL THINKING. THE SPREAD OF
THE SURFACE LOW DUE TO THE ANTICYCLONIC LOOP BETWEEN LONG ISLAND
AND BERMUDA.
---PRIOR DISCUSSION---
THERE CONTINUES TO BE NEAR-TERM SOLID AGREEMENT THROUGH ABOUT
48HRS (23.12Z) AS THE CLOSED LOW STARTS TO BE PICKED UP INTO THE
NORTHERN STREAM AND MOVE THROUGH THE MID-ATLANTIC. THE 12Z
NAM/GFS CONTINUE TO BE SLIGHTLY OUTWARD FROM THE CENTER OF
ANTICYCLONIC LOOPING AND FURTHER INTO THE NORTHERN STREAM AS THE
SURFACE WAVE DEVELOPS ALONG THE HUDSON CANYON/NEW YORK BIGHT
REGION OF THE NW ATLANTIC. THE CMC/ECMWF ARE MUCH TIGHTER TO THE
ANTICYCLONIC LOOP AND THEREFORE SOUTH AND WEST ESPECIALLY BY
SUNDAY. ENSEMBLE SUITE/TRENDS WOULD SUPPORT THIS TIGHTER
ROTATION SOLUTION BUT THE GFS/NAM REMAIN CLOSE ENOUGH TO BE VIABLE
IN A GENERAL MODEL BLEND THROUGHOUT THE SHORT-TERM FORECAST
PERIOD. CONFIDENCE IS ABOVE AVERAGE.
..DEEP UPPER TROUGH/CLOSED LOW OVER THE NORTHERN HIGH PLAINS
...SECONDARY UPPER DIGGING UNDERNEATH ACROSS NORTHERN ROCKIES,
EJECTING INTO NORTHERN PLAINS BY LATE SAT/EARLY SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z ECMWF TRENDED MUCH SLOWER, IN FACT, MOVING TO
ONE OF THE SLOWEST MEMBERS WITH THE SHORTWAVE EMERGING OUT OF THE
NORTH-CENTRAL ROCKIES AND SO THE SURFACE EVOLUTION IS NOW IN LINE
WITH THE REMAINDER OF THE GUIDANCE, AND IT MAKES THE GFS LOOK MORE
NORMAL BEING A BIT TOO FAST AND WITH THE SHIFT OF THE GEFS FURTHER
SOUTH, A GENERAL MODEL BLEND IS SUPPORTED THROUGHOUT THE
SHORT-TERM FORECAST, WITH NO INCREASE OF WEIGHTING DESIRED, AS
SUCH WILL HAVE SLIGHTLY ABOVE AVERAGE CONFIDENCE THROUGHOUT THE
REMAINDER OF THE FORECAST PERIOD AS WELL.
---PRIOR DISCUSSION---
GOES-WV SUITE DENOTES A CLOSED LOW CURRENTLY IN EASTERN MT IS
LIFTING INTO CANADA, WITH A REPLACEMENT CLOSED LOW/SHORTWAVE
ACROSS SW BC/VANCOUVER ISLAND STARTING TO UNDERCUT THE LARGER LOW.
THIS WAVE WILL ELONGATE THE LARGER SCALE TROF INTO THE CENTRAL
ROCKIES BY SAT. UNCHARACTERISTICALLY, THE 00Z ECMWF IS A BIT TOO
FAST BOTTOMING OUT FURTHER WEST IN SE ID, WHILE THE UKMET/NAM/CMC
SUGGEST A SMALL CLOSED LOW IN N UT/SW WY. THIS LEADS TO AN
EARLIER AND NORTHWARD SURFACE WAVE DEVELOPMENT THROUGH THE
NORTHERN PLAINS. THE 06Z GEFS AND 00Z ECENS MEAN, SUPPORT THIS
NORTHERN SOLUTION TO A POINT BUT ARE GENERALLY WASHED OUT WITH
SOLID AMOUNTS OF UNCERTAINTY. THE NAM/CMC/UKMET ALL GENERALLY
MUCH FURTHER SOUTH AND SLOWER TO DEVELOP; THE UKMET MAY BE A BIT
OFF IN TIMING GIVEN ITS DOWNSTREAM WEAKNESS. THE 12Z GFS FURTHER
SLOWED AND MOVED TOWARD THE FRINGE OF THE GEFS SOLUTIONS BUT
NEARER THE NAM/CMC/UKMET EVOLUTION. THERE IS SUFFICIENT
UNCERTAINTY AND GIVEN THE GFS TREND, IS A BIT CONCERNING MOVING
AWAY FROM MORE RELIABLE/STATISTICALLY PREFERABLE SOLUTIONS;
HOWEVER, OBSERVATIONS, BROAD ENSEMBLE SPREAD AND THE ECMWF IN AN
UNCHARACTERISTIC POSITION RELATIVE TO THE REMAINDER OF THE SUITE
(NOT TO MENTION IMPORTANCE OF MESOSCALE PROCESSES FEEDING BACK TO
THE SYNOPTIC SCALE. AFTER 72HRS, THE UKMET IS WEAK, THE CMC IS
FASTER AND SHIFTS NORTHEAST WHILE THE GFS/NAM ARE MORE MIDDLE
GROUND SO WILL ADJUST WEIGHTING PREFERENCES ACCORDINGLY ACROSS THE
NORTHERN PLAINS. THERE MAY BE ENOUGH TO SUPPORT USING A NON-ECMWF
BLEND, HEDGING WEIGHTING TOWARD THE 12Z GFS AS MIDDLE-GROUND
COMPROMISE. CONFIDENCE IS INITIALLY SLIGHTLY ABOVE AVERAGE BUT
DECREASES AFTER 60HRS AS THE ECMWF MOVES TOO FAST RELATIVE TO THE
SUITE, BECOMING SLIGHTLY BELOW AVERAGE
..SHORTWAVE LIFTING NORTHEAST ACROSS THE MIDWEST BY LATE FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: 12Z UKMET IS A BIT STRONGER BUT REMAINS TOO WEAK TO
INCLUDE IN THE BLEND, AS SUCH A NON-UKMET BLEND REMAINS PREFERRED
FOR THIS SYSTEM.
---PRIOR DISCUSSION---
A SHORTWAVE OVER THE SOUTHERN ROCKIES IS EMERGING INTO THE CENTRAL
PLAINS TONIGHT (FRIDAY MORNING), SETTING OFF SOME CONVECTIVE
DEVELOPMENT AND UPSCALE ENHANCEMENT OF THE WAVE. THE MAGNITUDE
AND PLACEMENT OF THE LATENT HEAT RELEASE AND UPSCALE GROWTH IS KEY
TO FUTURE EVOLUTION. THE 12Z GFS AND NAM CONTINUE TO BE A BIT
STRONGER AND MORE COMPACT (THE NAM MORE BROAD, THE GFS A BIT MORE
COMPACT). THE 00Z UKMET IS VERY WEAK AND GENERALLY FASTER WITH
THE WAVE WHILE THE CMC/ECMWF ARE WEAKER THAN THE GFS/NAM BUT
GENERALLY BETTER TIMED THAN THE FASTER UKMET. THIS IS KEY TO THE
DOWNSTREAM EVOLUTION THROUGH THE UPPER-MIDWEST AND DEPENDING ON
THE STRENGTH OF THE MID-LEVEL WAVE, HOW GREAT IT SHEARS AS IT
OVER-TOPS THE RIDGE IN THE GREAT LAKES ON SUNDAY. SO IN GENERAL,
THE UKMET IS NOT FAVORED GIVEN THE CURRENT ENVIRONMENTAL SETUP IN
THE PLAINS, SUGGESTING THE GFS/NAM/ECMWF/CMC ARE MORE ALIGNED.
WITHIN THIS NON-UKMET A PREFERENCE TOWARD A COMPROMISE IN
TIMING/PLACEMENT OF THE GFS/ECMWF ARE PREFERRED. GIVEN THE
IMPORTANCE OF THE UPSCALE ENHANCEMENT OF THE WAVE TO THE OVERALL
EVOLUTION, YET THERE IS SOLID AGREEMENT IN THE SYNOPTIC EVOLUTION
TO HAVE THIS SLIGHTLY ABOVE AVERAGE CONFIDENCE IN THE BLEND.
..SOUTHERN PLAINS SHORTWAVE DEVELOPING SUN INTO MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS AND 00Z ECMWF BLEND
CONFIDENCE: BELOW AVERAGE
19Z UPDATE: THE 12Z ECMWF TRENDED A BIT DEEPER AND EAST PUSHING IT
A BIT CLOSER TO THE GFS, WHILE THE UKMET AND CMC CONTINUE TO BE
VERY SIMILAR TO THEIR PRIOR SOLUTIONS. AS SUCH WILL KEEP A
GFS/ECMWF BLEND PREFERENCE AT BELOW AVERAGE CONFIDENCE GIVEN THE
IMPORTANCE OF CONVECTIVE FEATURES, OUTFLOW AND RETURN MOISTURE
THAT ARE VERY HARD TO DELINEATE AT DUE TO THE CHAOTIC NATURE OF
CONVECTIVELY INDUCED BOUNDARIES AND CLOUD COVER MESSING WITH
INSTABILITY IN THE NEAREST TERM.
---PRIOR DISCUSSION---
THE BASE OF THE ELONGATED WESTERN LARGE SCALE TROF WILL BRING
BROAD SOUTHWESTERLY FLOW AND PERIPHERY OF JET ENERGY TO INTERSECT
THE RETURN GULF MOISTURE THROUGH THE PECOS RIVER VALLEY INTO THE
RIO GRANDE. AS SUCH A CONVECTIVE COMPLEX WILL HELP TO SUPPORT A
SHORTWAVE/MCV DEVELOPMENT BY EARLY SUNDAY ACROSS TX WITH THE
POTENTIAL FOR A PACIFIC STREAM SHORTWAVE TO RE-ENERGIZE THE BASE
OF THE WESTERN TROF. THE 12Z NAM IS A CLEAR OUTLIER EARLY GIVEN
A VERY STRONG RESPONSE/WITH UNREALISTIC CONVECTIVE FEEDBACK,
LIKELY SOME GRID-SCALE FEEDBACK, BUT MORE IMPORTANTLY MUCH FURTHER
NORTH. THE GFS SEEMS GOOD IN TIMING/PLACEMENT ALONG WITH THE CMC
AND UKMET; HOWEVER, THE UKMET AND CMC SHOW VERY STRONG CONVECTIVE
RESPONSE NEARER THE GULF ON LATE SUNDAY. WHILE PLAUSIBLE, THEIR
CONVECTIVE COMPLEX MAGNITUDES/UPSCALE FEEDBACK MAY BE IN THE SAME
REALM AS THE UNFAVORED NAM. THE 12Z ECMWF IS SLOWER AND WEAKER
WITH THE UPSCALE DEVELOPMENT BUT IS ALSO A TAD SLOWER HAVING A
SLIGHTLY STRONGER PACIFIC STREAM, BASE OF THE LARGE SCALE WESTERN
TROF LATE SUNDAY. STILL, THIS SEEMS MORE SENSIBLE GIVEN THE
UNCERTAINTY/IMPORTANCE OF CONVECTIVE UPSCALE...WILL SUPPORT A 12Z
GFS AND 00Z ECMWF BLEND BUT AT BELOW AVERAGE CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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