356
FXUS10 KWNH 200533
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1233 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 NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
..SHORTWAVE/FRONT CLIPPING THE PACIFIC NORTHWEST MONDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: 12Z ECMWF/CMC 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 WHILE THE 12Z UKMET IS
SLOWER. THE ENSEMBLE MEANS FAVOR A BLEND OF THE 12Z ECMWF AND 12Z
CMC, THROUGH A NON-NAM BLEND WILL ALSO SUFFICE FOR THIS SYSTEM.
..SOUTHERN STREAM SHORTWAVE CROSSING CALIFORNIA BY MONDAY
..ENERGY CROSSING THE SOUTHWEST/PLAINS TUESDAY AND WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: 00Z NAM/12Z ECMWF 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 12Z ECMWF (WHICH LIES
BETWEEN ITS ENSEMBLE MEAN AND THE NAM). THE 12Z UKMET APPEARS TOO
SLOW WHILE THE 12Z CMC ALSO APPEARS A TAD FASTER. OVERALL, A BLEND
BETWEEN THE 12Z ECMWF WITH THE FASTER 00Z NAM APPEARS 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...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF/12Z CMC
CONFIDENCE: SLIGHTLY BELOW AVERAGE
SOME LATITUDE DIFFERENCES CONTINUE TO EXIST WITH THIS SYSTEM AS IT
APPROACH THE PACIFIC NORTHWEST ON TUESDAY WITH THE 12Z 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, 12Z ECMWF
AND 12Z 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...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: 00Z GFS/12Z ECMWF 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 IS FASTEST
AND 12Z 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
12Z ECMWF 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
OTTO
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