425
FXUS10 KWNH 221911
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 PM EDT WED JUL 22 2020
VALID JUL 22/1200 UTC THRU JUL 26/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...BROAD GREAT LAKES TROUGH AXIS AND CORRESPONDING COLD FRONT
IMPACTING THE OH VALLEY, NORTHEAST AND MID-ATLANTIC INTO
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z GFS AND 12Z ECMWF BLEND
CONFIDENCE: AVERAGE
19Z UPDATE...NO SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z CYCLES.
PREVIOUS DISCUSSION BELOW...
TIMING DIFFERENCES REGARDING THE EASTWARD TRACKING GREAT LAKES
TROUGH SHOW UP LATE THURSDAY WITH THE 00Z UKMET SLOWING RELATIVE
TO THE REMAINING DETERMINISTIC/ENSEMBLE CONSENSUS. THE 00Z UKMET
ALSO SHOWS THE STRONGEST DEPICTION OF THE CENTRAL CONUS RIDGE
WHICH MAY HAVE IMPACTS ON DOWNSTREAM TROUGHING ACROSS THE
NORTHEAST OVER THE WEEKEND. MEANWHILE, THE 00Z CMC STANDS OUT WITH
GREATER AMPLIFICATION OF THE TROUGH AXIS NEAR THE EAST COAST
SATURDAY MORNING WITH ENSEMBLE SPAGHETTI PLOTS OF THE 500 MB 588
DAM HEIGHT CONTOUR SUPPORTING GREATER CLUSTERING AROUND THE 12Z
NAM, 12Z GFS AND 00Z ECMWF MODELS. THE 06Z GEFS MEAN CONTINUES TO
STAND OUT WITH GREATER AMPLIFICATION OF THE MID-LEVEL TROUGH OVER
THE EAST COAST AS WELL. THEREFORE, THE PREFERENCE CENTERS AROUND
GREATER ENSEMBLE/DETERMINISTIC SUPPORT AND STAYING CLEAR OF
OUTLIERS SINCE TRENDS OVER THE PAST FOUR 12/00Z CYCLES SEEM TO
SUPPORT THE MIDDLE GROUND.
..MID-UPPER LEVEL TROUGHING IMPACTING THE NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
19Z UPDATE...THE 12Z ECMWF/UKMET/CMC TRENDED SLIGHTLY FASTER/SOUTH
COMPARED TO THEIR PREVIOUS 00Z CYCLES MAKING MODEL AGREEMENT
BETTER THAN THE EARLIER GUIDANCE, DESPITE SOME MINOR TIMING
DIFFERENCES THAT REMAIN.
PREVIOUS DISCUSSION BELOW...
AFTER THE DEPARTURE OF A SHORTWAVE TROUGH OVER WASHINGTON
(THURSDAY MORNING), THE SOUTHERN PORTION OF A SECOND TROUGH IS
EXPECTED TO PASS OVER THE NORTHWEST ON FRIDAY/SATURDAY BEFORE
ADVANCING EASTWARD TOWARD THE NORTHERN HIGH PLAINS FOR SATURDAY
EVENING. THE 12Z NAM/GFS ARE SLIGHTLY FASTER AND STRONGER WITH THE
SECOND TROUGH AXIS AFFECTING THE NORTHWEST ON SATURDAY COMPARED TO
THE 00Z ECMWF/UKMET/CMC. HOWEVER, THE ENSEMBLE MEANS APPEAR TO
SPLIT THE DIFFERENCE WITH A GENERAL MODEL BLEND LIKELY BEST ACROSS
THE NORTHWESTERN U.S.
..CALIFORNIA/SOUTHWEST U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
19Z UPDATE...TIMING ADJUSTMENTS WERE NOTED WITH THE UT SHORTWAVE
FROM THE 12Z ECMWF/CMC TO MATCH THE REMAINING MODEL CONSENSUS.
OTHERWISE, NO SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z CYCLES.
PREVIOUS DISCUSSION BELOW...
A SERIES OF SYSTEMS WILL IMPACT THE SOUTHWESTERN U.S. OVER THE
NEXT FEW DAYS. FIRST, A NEGATIVELY TILTED MID-LEVEL TROUGH AXIS
WILL TRACK FROM UT THIS MORNING INTO THE NORTHERN HIGH PLAINS FOR
THURSDAY EVENING. MINOR TIMING DIFFERENCES HERE, WITH THE 00Z
ECMWF SLIGHTLY FASTER AND 00Z CMC SLIGHTLY SLOWER. SECOND, A
CLOSED LOW OVER CENTRAL CA IS EXPECTED TO WEAKEN WITH AN EASTWARD
OR SOUTHEASTWARD PROGRESSION INTO INTERIOR PORTIONS OF THE WEST.
AFTER THE DEPARTURE OF THE CLOSED LOW FROM CA, ANOTHER DISTURBANCE
(WEAKER THAN THE PREVIOUS LOW) WILL REACH THE CA COAST LATE ON
SATURDAY.
THE MODELS ALL SHOW DECENT AGREEMENT WITH ALL OF THESE FEATURES
WITH NO SINGLE MODEL DIFFERING ENOUGH TO EXCLUDE IT FROM THE
PREFERENCE.
..EASTERLY WAVE MOVING THROUGH THE GULF OF MEXICO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z GFS, 12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
19Z UPDATE...NO SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z CYCLES, THOUGH
THERE IS GENERALLY A NON-NCEP CAMP OF MODELS THAT SHOWS MORE
ORGANIZATION/SYMMETRY WITH THE MID-LEVEL LOW VERSUS THE MORE
DISORGANIZED 12Z NAM/GFS. ENSEMBLE MEANS ARE BETWEEN THE TWO
CAMPS.
PREVIOUS DISCUSSION BELOW...
ALL OF THE MODELS SHOW A SIMILAR DEPICTION REGARDING A LOW TO
MID-LEVEL TROUGH AXIS/LOW ADVANCING WESTWARD ACROSS THE GULF OF
MEXICO THROUGH SATURDAY, REACHING THE TEXAS COAST SOMETIME FRIDAY
NIGHT OR SATURDAY MORNING. THE 00Z UKMET IS THE STRONGEST OF THE
LATEST MODEL GUIDANCE, FOLLOWED NEXT BY THE 00Z CMC. THE
NAM/GFS/ECMWF SHOW VARYING DEGREES OF STRENGTH BUT SIMILAR
POSITION AND TIMING OVER THE NEXT COUPLE OF DAYS. THE 12Z GFS IS A
BIT WEAKER AND THE 00Z ECMWF STALLS THE SYSTEM NEAR THE MIDDLE
TEXAS COAST ON SATURDAY WHICH IS NOT SUPPORTED IN A MAJORITY OF
THE AVAILABLE ENSEMBLE GUIDANCE. THE 12Z NAM IS ALSO A BIT WEAKER
BUT SPLITS THE DIFFERENCE IN STRENGTH BETWEEN THE WEAKER 12Z GFS
AND STRONGER 00Z ECMWF.
THE NATIONAL HURRICANE CENTER IS MONITORING THIS AREA FOR TROPICAL
CYCLONE FORMATION, SHOWING A 50 PERCENT CHANCE OF DEVELOPMENT OVER
THE NEXT 5 DAYS. IT SHOULD BE NOTED THAT SCATTER LOW ENSEMBLE PLOT
SPREAD IS MODERATE AND BOTH DETERMINISTIC AND ENSEMBLE GUIDANCE
HAS SHOWN A UNANIMOUS TREND TO BE SLOWER WITH THE WESTWARD
PROGRESSION OF THE LOW LEVEL WAVE COMPARED TO MODEL RUNS FROM
YESTERDAY.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
OTTO
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