088
FXUS10 KWNH 220451
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1250 AM EDT SUN SEP 22 2019
VALID SEP 22/0000 UTC THRU SEP 25/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..SYNOPTIC OVERVIEW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE SYNOPTIC PATTERN WILL FEATURE A DEEP LAYER RIDGE OVER THE
SOUTHEAST THROUGH SUNDAY, AS A PAIR OF ROBUST NORTHERN STREAM
TROUGHS TRAVERSE THE WESTERN AND CENTRAL U.S. THE FIRST TROUGH
WILL ADVANCE EAST ACROSS THE UPPER MIDWEST THROUGH SUNDAY ALONG
WITH AN ATTENDANT COLD FRONT AND A WAVE OF LOW PRESSURE RIDING UP
ALONG IT. THIS ENERGY WILL BREAK DOWN THE RIDGE OVER THE SOUTHEAST
AND ALLOW A COLD FRONT TO ARRIVE ACROSS THE OH VALLEY AND LOWER
GREAT LAKES REGION BY MONDAY. THE HEIGHT FALLS ARE EXPECTED TO
SHARPEN OVER THE NORTHEAST BY TUESDAY AS AN UPPER LOW DEEPENS AND
FOSTERS CYCLOGENESIS OVER NORTHERN NEW ENGLAND. THIS WILL ADVANCE
THE UPSTREAM COLD FRONT ACROSS THE EAST COAST. MEANWHILE, A SECOND
UPSTREAM TROUGH WILL CROSS THE WEST COAST AND MOVE INTO THE GREAT
BASIN BY MONDAY BEFORE THEN CUTTING OFF FROM THE WESTERLIES AND
DROPPING DOWN INTO THE SOUTHWEST ON TUESDAY. THIS UPPER TROUGH
WILL TAP SOME OF THE REMAINING MOISTURE AND ENERGY ASSOCIATED WITH
WEAKENING TROPICAL STORM LORENA WHICH WILL BE CROSSING NORTHWEST
MEXICO. BY TUESDAY AND WEDNESDAY, A NEW NORTHERN STREAM TROUGH
WILL DIG ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST ALONG WITH A
COLD FRONT.
..DEEP TROUGH CROSSING THE PLAINS/MIDWEST THROUGH SUNDAY
..ENERGY CLOSING OFF OVER THE NORTHEAST EARLY NEXT WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 60 HOURS
NON-GFS BLEND...AFTER 60 HOURS
CONFIDENCE: ABOVE AVERAGE
MODEL DIFFERENCES WITH THE FIRST TROUGH ARE RATHER SMALL THROUGH
MOST OF THE WEEKEND AS THE ENERGY CROSSES THE INTERMOUNTAIN WEST
AND ADVANCES ACROSS THE PLAINS AND MIDWEST, BUT BY LATER MONDAY
AND TUESDAY AS THE ENERGY CROSSES THE GREAT LAKES AND MOVES INTO
THE NORTHEAST, THE 00Z GFS BECOMES A BIT MORE PROGRESSIVE THAN THE
REMAINING WELL CLUSTERED GUIDANCE. WILL RECOMMEND A GENERAL MODEL
BLEND THROUGH ABOUT 60 HOURS, AND THEN A NON-GFS BLEND THEREAFTER.
..UPPER TROUGH DIGGING INTO THE WEST BY MONDAY
..CLOSED LOW EVOLUTION OVER THE SOUTHWEST BY TUESDAY
..MOISTURE/ENERGY ASSOCIATED WITH T.S. LORENA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/GFS AND 12Z ECMWF
CONFIDENCE: AVERAGE...BECOMING BELOW AVERAGE BY TUESDAY
REGARDING THE SECOND TROUGH MOVING INTO THE WEST, THE MODEL
GUIDANCE IS WELL CLUSTERED AND IN GOOD AGREEMENT WITH RESPECT TO
TIMING AND DEPTH THROUGH MOST OF MONDAY. HOWEVER, BY MONDAY NIGHT
AND TUESDAY AS THE ENERGY CUTS OFF AND DROPS SOUTH INTO THE
SOUTHWEST, THE 12Z CMC SUGGESTS A FASTER AND SOMEWHAT WEAKER
EVOLUTION WHICH ALLOWS THE HEIGHT FALLS TO ADVANCE MORE BODILY
ACROSS THE FOUR CORNERS VERSUS BEING MORE CONCENTRATED ACROSS
SOUTHEAST CA AND AZ. THE 00Z NAM/GFS AND 12Z ECMWF ARE VERY WELL
CLUSTERED ON A MORE COMPACT CLOSED LOW EVOLUTION THAT ULTIMATE
ALLOWS THE CLOSED LOW TO CROSS THE DESERT SOUTHWEST AND THEN DROP
INTO THE FAR NORTHERN GULF OF CA AND THE IMMEDIATE ADJACENT AREAS
OF NORTHWEST MEXICO. THE 12Z UKMET IS A TAD EAST OF THIS
CONSENSUS. THE ENSEMBLE MEANS FOSTER SOME INCREASED UNCERTAINTY IN
THE FORECAST AS THE 12Z ECENS MEAN BASICALLY MIMICS THE UKMET AND
THE 18Z GEFS MEAN FAVORS A SOLUTION IN BETWEEN THE UKMET AND CMC,
AND ULTIMATELY EAST OF THE NAM/GFS/ECMWF CLUSTER. ALL OF THE
MODELS DO INDICATE SOME INTERACTION WITH THE REMNANT MOISTURE AND
ENERGY ASSOCIATED WITH WEAKENING TROPICAL STORM LORENA WHICH IS
EXPECTED TO LIFT ACROSS NORTHWEST MEXICO SUNDAY BEFORE THEN
DISSIPATING SUNDAY NIGHT. FOR NOW, A BLEND OF THE 00Z NAM/GFS AND
12Z ECMWF WILL BE PREFERRED, BUT CONFIDENCE BECOMES A TAD LIMITED
BY THE END OF THE PERIOD GIVEN SOME OF THE MODEL MASS FIELD SPREAD
BY THAT TIME.
..UPPER TROUGH OVER THE NORTHERN PLAINS BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 60 HOURS
NON-GFS BLEND...AFTER 60 HOURS
CONFIDENCE: ABOVE AVERAGE
THE MODELS HAVE GOOD AGREEMENT OVERALL WITH THE DETAILS OF A
NORTHERN STREAM TROUGH AND ASSOCIATED COLD FRONT CROSSING THE
NORTHERN HIGH PLAINS BY TUESDAY AND UPPER MIDWEST BY WEDNESDAY.
THE 00Z GFS IS JUST A TAD SHARPER AND MORE PROGRESSIVE THAN THE
REMAINING GUIDANCE TOWARD THE END OF THE PERIOD. THE 18Z GEFS MEAN
SUGGESTS A MODESTLY SLOWER SOLUTION THAT IS CLOSER TO THE
REMAINING WELL-CLUSTERED MULTI-MODEL CONSENSUS. SO, WILL PREFER A
GENERAL MODEL BLEND THROUGH ABOUT 60 HOURS, AND A NON-GFS BLEND
THEREAFTER.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
ORRISON
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