191
FXUS10 KWNH 200649
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 AM EST MON JAN 20 2020
VALID JAN 20/0000 UTC THRU JAN 23/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
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..SHORTWAVE/FRONT CLIPPING THE PACIFIC NORTHWEST MONDAY MORNING
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~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
DIFFERENCES WITH THIS SYSTEM ARE VERY MINOR AND SO THEREFORE, A
GENERAL MODEL BLEND WILL BE PREFERRED.
..AMPLIFYING SHORTWAVE CROSSING THE MIDWEST THROUGH MONDAY
..CLOSED LOW EVOLUTION OVER THE SOUTHEAST BY TUESDAY
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~~
PREFERENCE: NON 00Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
AS A SHORTWAVE AMPLIFIES SOUTHEASTWARD ACROSS THE MISSISSIPPI
RIVER, IT IS EXPECTED TO CLOSE OFF ALONG THE SOUTHEAST AND MOVE
OUT INTO THE WESTERN ATLANTIC. THE 00Z NAM ENDS UP DEEPEST AND
NORTH OF THE FAVORED POSITION OF THE LATEST ENSEMBLE MEANS. THE
00Z GFS IS ALSO A TAD NORTH OF IDEAL BUT QUICKER TRENDS FROM THE
00Z UKMET/CMC (RELATIVE TO THEIR PREVIOUS 12Z CYCLES) ALONG WITH
THE CONSISTENT ECMWF SUPPORTS A GENERAL NON-00Z NAM BLEND FOR THIS
SYSTEM.
..SOUTHERN STREAM SHORTWAVE CROSSING CALIFORNIA BY MONDAY
..ENERGY CROSSING THE SOUTHWEST/PLAINS TUESDAY AND WEDNESDAY
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PREFERENCE: 00Z NAM/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
THE 00Z GFS CONTINUES TO APPEAR TOO FAST AS THE SHORTWAVE REACHES
THE GREAT PLAINS AND BEYOND AS THE FEATURE APPROACHES THE
MISSISSIPPI RIVER. THIS IS REFLECTED IN THE LATEST ENSEMBLE
GUIDANCE VALID TUESDAY EVENING AS WELL WITH THE GFS LEADING THE
PACK OF THE GEFS SPAGHETTI PLOTS, WHILE THE ECMWF MEMBERS TRAIL
THE REMAINING GUIDANCE. THE 00Z NAM IS IN THE MIDDLE REGARDING
TIMING, FOLLOWED BY THE DETERMINISTIC 00Z ECMWF AND 00Z UKMET
(WHICH BOTH SPED UP FROM THEIR PREVIOUS 12Z CYCLES AND ARE FASTER
THAN THE ECMWF ENSEMBLE MEAN). THE 00Z CMC DID NOT CHANGE MUCH
FROM ITS PREVIOUS 12Z CYCLE AND CONTINUES TO APPEAR TOO FAST.
OVERALL, A BLEND BETWEEN THE 00Z ECMWF WITH THE 00Z NAM AND 00Z
UKMET SHOULD WORK BEST FOR THIS SYSTEM AS ENSEMBLE TRENDS APPEAR
TO BE APPROACHING THE MIDDLE GROUND.
..UPPER TROUGH/CLOSED LOW OVER THE PACIFIC NORTHWEST BY TUESDAY
...ENERGY EJECTING OUT ACROSS THE NORTHERN PLAINS WEDNESDAY
NIGHT...
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~~
PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/CMC
CONFIDENCE: SLIGHTLY BELOW AVERAGE
SOME LATITUDE DIFFERENCES CONTINUE TO EXIST WITH THIS SYSTEM AS IT
APPROACH THE PACIFIC NORTHWEST ON TUESDAY WITH THE 00Z ECMWF/UKMET
NORTH WITH THE CENTER OF THE CLOSED LOW WHILE THE 00Z NAM IS
SOUTH. THESE DIFFERENCES AMPLIFY DOWNSTREAM INTO INTERIOR PORTIONS
OF THE NORTHWEST, DOWNSTREAM OF A LONGWAVE RIDGE CENTERED OVER THE
EASTERN PACIFIC. AT THIS TIME, A MIDDLE GROUND IS FAVORED WHICH
CURRENTLY IS BEST REPRESENTED BY A BLEND OF THE 00Z GFS, 00Z ECMWF
AND 00Z CMC, NOTING THAT THERE WAS A SMALL TREND TO BE FASTER AS
THE TROUGH AXIS REACHES THE NORTHERN PLAINS IN THE 00Z ECMWF/CMC.
GIVEN ABOVE AVERAGE ENSEMBLE SPREAD AND COMPLEX EVOLUTION OF THE
DOWNSTREAM TROUGH GIVEN MULTIPLE EMBEDDED VORTICITY MAXIMA,
CONFIDENCE IS A LITTLE BELOW AVERAGE FOR THIS SYSTEM.
...UPSTREAM MID-LEVEL TROUGH OFFSHORE OF THE PACIFIC NORTHWEST
EARLY THURSDAY ALONG WITH ACCOMPANYING SURFACE CYCLONE...
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PREFERENCE: 00Z GFS/UKMET BLEND
CONFIDENCE: AVERAGE
TIMING DIFFERENCES APPEAR TO BE THE SIGNIFICANT REASON FOR MODEL
DIFFERENCES WITH AN UPSTREAM, SHALLOW AMPLITUDE LONGWAVE TROUGH TO
NEAR THE PACIFIC NORTHWEST WEDNESDAY NIGHT. THE 00Z NAM/ECMWF ARE
FASTEST AND 00Z CMC SLOWEST WITH THE LEADING SHORTWAVE. THERE ARE
MODEST DIFFERENCES REFLECTED IN THE ENSEMBLE SPREAD AND GIVEN THE
SOURCE REGION FOR THIS SYSTEM IS AN AREA OF HIGHER UNCERTAINTY,
WILL PREFER TO GO IN THE MIDDLE OF THE SPREAD TOWARD THE 00Z GFS
AND 00Z UKMET AT THIS TIME.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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