873
FXUS10 KWNH 031856
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EST FRI JAN 03 2020
VALID JAN 03/1200 UTC THRU JAN 07/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..AMPLIFYING LONGWAVE TROUGH ACROSS THE CENTRAL U.S.
...SURFACE LOW TRACKING FROM THE OHIO VALLEY TO OFFSHORE NEW
ENGLAND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z GFS BLEND
CONFIDENCE: AVERAGE
MODEL SPREAD CONCERNING THE INTERACTION BETWEEN TWO PIECES OF
ENERGY WITHIN A LONGWAVE TROUGH SHIFTING EASTWARD HAS DIMINISHED
CONSIDERABLY COMPARED TO PREVIOUS DAYS. HOWEVER, SOME MINOR TIMING
DIFFERENCES REMAIN WITH THE 500 MB TROUGH AXIS WHICH RESULTS IN
DIFFERING PLACEMENTS OF THE CORRESPONDING SURFACE LOW TO TRACK
EAST-NORTHEASTWARD JUST SOUTH OF NEW ENGLAND ON SATURDAY. THE 12Z
GFS APPEARS A BIT FAST COMPARED TO THE LATEST
DETERMINISTIC/ENSEMBLE SPREAD. THE GEFS/EC ENSEMBLE MEANS ALSO
SUPPORT A SLOWER TRACK THAN THE 12Z GFS WITH THE 12Z NAM AND 00Z
ECMWF CLOSEST TO WHAT IS CONSIDERED BEST FOR THIS SYSTEM. THE 12Z
ECMWF/UKMET/CMC MADE MINOR ADJUSTMENTS BUT CONTINUE TO SUPPORT A
NON 12Z GFS BLEND.
..SHORTWAVE TROUGH/LOW IMPACTING THE PACIFIC NORTHWEST
..ENERGY EJECTING OUT ACROSS THE PLAINS/MIDWEST BY SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z CMC BLEND
CONFIDENCE: AVERAGE
THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE SHORTWAVE
TRACKING FROM THE PACIFIC NORTHWEST FRIDAY NIGHT TOWARD THE GREAT
LAKES REGION SUNDAY NIGHT. THE 12Z NAM/GFS ARE ORIENTED FARTHER
NORTH WITH THE NEGATIVELY TILTED TROUGH AXIS EXTENDING FROM THE
UPPER MISSISSIPPI VALLEY TO THE UPPER OHIO VALLEY SUNDAY EVENING
COMPARED TO THE 00Z ECMWF/UKMET/CMC. THE 00Z CMC IS SLOWEST AND
FARTHEST SOUTH, SO IT WILL BE DISCOUNTED GIVEN BETTER AGREEMENT
FOR A BLEND BETWEEN THE NAM/GFS AND ECMWF/UKMET FORECASTS. NO
SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES.
..SPLIT FLOW TROUGH NEAR THE PACIFIC NORTHWEST BY SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z CMC BLEND
CONFIDENCE: AVERAGE
SIMILAR TO THE ABOVE SYSTEM, MODEL SPREAD IS SMALL WITH THE
MID-LEVEL TROUGH AXIS REACHING THE PACIFIC NORTHWEST ON SUNDAY.
HOWEVER, THE 00Z AND 12Z CMC STAND OUT AS SLOW COMPARED TO THE
REMAINING AVAILABLE GUIDANCE BY LATE MONDAY. THEREFORE, WHILE
DIFFERENCES ARE RELATIVELY MINOR, A NON CMC BLEND WILL BE
PREFERRED FOR THIS SYSTEM.
...UPSTREAM SHORTWAVE OFF OF THE PACIFIC NORTHWEST MONDAY
EVENING...
..WARM FRONTAL TIMING INTO THE PACIFIC NORTHWEST ON MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z GFS, 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
MODERATE SPREAD EXISTS WITH AN UPSTREAM SHORTWAVE TROUGH AXIS
LOCATED ROUGHLY 1000 MILES OFF OF THE COAST OF THE PACIFIC
NORTHWEST 00Z/07. THE 12Z ECMWF WAS STRONGEST WITH THE
CORRESPONDING SURFACE LOW AND TOWARD THE SOUTHERN SIDE OF THE
LATEST WIDE ENSEMBLE BASED SCATTER LOW PLOTS. BOTH THE 12Z ECMWF
AND CMC WERE FASTER THAN THE ENSEMBLE MEANS SO A BLEND OF THE 12Z
NAM/GFS/UKMET IS PREFERRED WITH THIS SYSTEM GIVEN THEIR BETTER
PLACEMENT WITH RESPECT TO THE MIDDLE OF THE LATEST ENSEMBLE
DISTRIBUTION.
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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