532
FXUS10 KWNH 221853
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 PM EDT FRI MAY 22 2020
VALID MAY 22/1200 UTC THRU MAY 26/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CUT-OFF LOW IMPACTING THE OH VALLEY AND NORTHERN MID-ATLANTIC
INTO SUNDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
ONLY MINOR TIMING DIFFERENCES EXIST WITH THIS SYSTEM WITH THE 12Z
GFS FASTEST. THE 12Z UKMET SPED UP FROM ITS PREVIOUSLY SLOWER
CYCLE. THE DIFFERENCES ARE GREATEST AFTER THE SYSTEM MOVES
OFFSHORE OF THE EAST COAST AND SO A GENERAL MODEL BLEND SHOULD
SUFFICE FOR THIS SYSTEM.
..DEEP UPPER TROUGH/CLOSED LOW RELOADING OVER THE WESTERN U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 12Z NAM AND 12Z GFS STAND OUT EARLY IN THE PERIOD (SATURDAY
EVENING) WITH A FASTER PROGRESSION WITH A MID-LEVEL CLOSED LOW
TRACKING ACROSS THE GREAT BASIN, BUT THE 12Z ECMWF/UKMET/CMC SPED
UP CLOSER TO THE NAM/GFS THROUGH SATURDAY NIGHT. BY SUNDAY MORNING
THE 12Z GFS PULLS AWAY FROM ALL OF THE GUIDANCE WITH A FASTER
PROGRESSION TOWARD THE NORTHERN PLAINS. MEANWHILE, ADDITIONAL
ENERGY WILL BE DIVING INTO THE WESTERN U.S., HELPING TO AMPLIFY A
LONGWAVE TROUGH AXIS THROUGH MONDAY.
WHILE TRENDS HAVE BEEN SLOWER OVER THE PAST 24-48 HOURS WITH THE
MEAN TROUGH AXIS TRANSLATING EASTWARD, THE 12Z GFS REMAINS FASTER
TO TAKE THE SYSTEM EAST, WHILE THE 00Z UKMET IS SLOWEST. THE 12Z
UKMET SPED UP WITH THE BASE OF THE TROUGH INTO MONDAY WHILE THE
12Z CMC REMAINS SIMILAR TO THE PREVIOUS CYCLE. THE 12Z ECMWF
NUDGED SLIGHTLY SLOWER WITH THIS FEATURE COMPARED TO ITS 00Z
CYCLE. THE 12Z NAM HAS SOME SIMILARITIES TO THE 00Z UKMET BY LATE
MONDAY BUT WHEN BLENDED WITH THE FASTER 12Z ECMWF, A FAVORABLE
BLEND IS REACHED. THE LATEST ENSEMBLE MEAN'S POSITION FOR THE
TROUGH AXIS IS A LITTLE SLOWER THAN THE 00Z ECMWF, NEAR THE 12Z
ECMWF BUT AHEAD OF THE 12Z NAM. GIVEN TRENDS IN THE ENSEMBLE
GUIDANCE, PREFER TO BE SLIGHTLY SLOWER THAN THE MEANS, ESPECIALLY
WHEN CONSIDERING THE POTENTIAL CUTOFF NATURE OF THIS SYSTEM MOVING
FORWARD.
...SHORTWAVE LIFTING NORTHEAST TOWARD THE GREAT LAKES THROUGH
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
GENERALLY THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM, BUT
THE 12Z GFS IS SLIGHTLY QUICKER AND THE 00Z UKMET IS NOTABLY
SLOWER. WITH THE 12Z UKMET ADJUSTING TOWARD THE REMAINING
CONSENSUS, A GENERAL MODEL BLEND CAN BE USED AT THIS TIME WITH
TIMING DIFFERENCES FAIRLY MINOR AT THIS POINT.
...ZONAL FLOW INTO PACIFIC NORTHWEST WITH EMBEDDED WEAK
SHORTWAVES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GFS BLEND
CONFIDENCE: AVERAGE
THERE ARE SOME MINOR DIFFERENCES WITHIN A REGION OF ZONAL FLOW
SANDWICHED BETWEEN A LARGE CLOSED LOW CENTERED OVER THE ALUETIANS
AND BROAD RIDGING IN THE EASTERN PACIFIC. LOW AMPLITUDE SHORTWAVES
ARE FORECAST WITHIN THE ZONAL FLOW WITH IMPACTS MAINLY TO BRITISH
COLUMBIA. HOWEVER, A SLIGHTLY MORE DEFINED SHORTWAVE IS EXPECTED
TO NEAR VANCOUVER ISLAND EARLY NEXT WEEK, ASSOCIATED WITH COLD
FRONT A THE SURFACE WHICH WILL EDGE NEARER TO THE COAST.
THE NAM/GFS HAVE BEEN TRENDING STRONGER WITH THIS WAVE SINCE
YESTERDAY BUT THE 12Z GFS STANDS OUT WITH LOWER HEIGHTS INTO THE
PACIFIC NORTHWEST WHICH IS AGAINST THE REMAINING MODEL CONSENSUS.
A NON-12Z GFS BLEND IS PREFERRED AT THIS TIME. NO SIGNIFICANT
CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR
PREVIOUS 00Z CYCLES.
...UPPER LEVEL SHORTWAVE LIFTING NORTHEAST ACROSS THE SOUTHERN
PLAINS SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GFS BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
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 SHORTWAVE TROUGH ROUNDING ITS BASE, LIFTING NORTHEAST
ACROSS THE SOUTHERN PLAINS ON SUNDAY. THERE IS POTENTIAL FOR
THUNDERSTORMS TO CONVECTIVE ENHANCE THE EXISTING SHORTWAVE OR
DEVELOP A SEPARATE CONVECTIVELY GENERATED VORTICITY MAX. SOME OF
THE GUIDANCE IS A BIT MORE BULLISH WITH THIS IDEA SUCH AS THE 00Z
UKMET AND 00Z CMC, BUT ONLY THE 12Z GFS STANDS OUT ENOUGH WITH A
FASTER TIMING (SIMILAR TO THE ABOVE SYSTEMS) TO BE EXCLUDED FROM
THE PREFERENCE. NO SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z CYCLES.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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