Prognostic Meteorological Discussion
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000
FXUS10 KWNH 160509
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
108 AM EDT WED APR 16 2014

VALID APR 16/0000 UTC THRU APR 19/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

==================================================
00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

...UPPER MIDWEST STORM LATER APPROACHING THE NORTHEAST IN A
WEAKENED STATE...

PREFERENCE: BLEND OF 00Z NAM/GFS WITH 12Z ECMWF

FOR MANY FEATURES ON THE MAP THE 12Z CANADIAN WAS OUT OF PHASE IN
BOTH DEPTH AND TIMING...AND THE UKMET WAS SLOW...AS IT WAS FOR
THIS SYSTEM. THE NAM/GFS/ECMWF FORM A STRONG CLUSTER OF
OPERATIONAL MODELS...SUPPORTED BY THE ENSEMBLE
MEANS...PARTICULARLY DURING THE EARLY LIFE OF THIS SYSTEM WHEN IT
WILL PRODUCE IMPACTFUL SNOWFALL ACROSS THE UPPER MIDWEST. SEE THE
HEAVY SNOW DISCUSSION...QPFHSD FROM THE WPC WINTER WEATHER DESK
FOR SNOWFALL DETAILS. 00Z RUNS OF THE NAM AND GFS TRENDED DEEPER
ALOFT ON DAY 1 WHICH HELPS PULL THE SURFACE LOW BACK WEST AND INTO
BETTER AGREEMENT WITH THE ECMWF. IN PLAN VIEW 850-700 MB PLOTS
THERE APPEARS TO BE STRONG CONSENSUS REGARDING THERMAL PROFILES.

FOLLOWING THIS INITIAL SHORTWAVE EVENT ANOTHER SHORTWAVE IN
SOUTHERN CANADA WILL SWING THROUGH THE BASE OF THE EXISTING
TROUGH. THE GFS IS CERTAINLY ONE OF THE DEEPEST SOLUTIONS AT 500
MB WITH THIS SECOND SHORTWAVE. AS OF YET THERE IS LITTLE SUPPORT
FOR THE GFS. DIFFERENCES BETWEEN THE GFS/NAM/ECMWF ARE LESS
PRONOUNCED FROM THE SURFACE TO 700 MB...BUT HEAVIER WEIGHT IS
RECOMMENDED ON THE NAM/ECMWF OVER THE EASTERN GREAT LAKES AND NEW
ENGLAND.


...SOUTHERN STREAM WAVE AMPLIFYING ALONG THE GULF COAST...

PREFERENCE: BLEND OF 12Z ECMWF/UKMET

A SHORTWAVE DIPPING INTO THE SOUTHERN PLAINS ON DAY 1 WILL PHASE
WITH AN ACTIVE SUB-TROPICAL JET TO ALLOW THE FORMATION OF A BROAD
BUT ORGANIZED BAROCLINIC SYSTEM IN THE GULF OF MEXICO. THERE IS AN
INCREASING MODEL SIGNAL FOR HEAVY RAIN IN FLORIDA THURSDAY AND
FRIDAY. THE MODELS VARY IN THEIR DEGREE OF PHASING AND THE DEPTH
THAT THE GULF SYSTEM ATTAINS. GENERALLY THE ECMWF/UKMET/CANADIAN
FORECAST A SIMILAR SYSTEM CONCEPTUALLY...ALTHOUGH THE CANADIAN IS
ON THE WEAK SIDE. THE PAST FEW RUNS OF THE NAM HAVE HANDLED THIS
SYSTEM IN A REASONABLE FASHION...BUT ITS SOLUTION IS ONE OF THE
DEEPEST AMONG OPERATIONAL MODELS AND THE ENSEMBLES. THE
PERFORMANCE OF THE NAM REGARDING LARGE SCALE SYSTEMS AT THIS
LATITUDE IS NOT USUALLY THE BEST...SO WE WILL NOT YET INCLUDE IT
IN OUR PREFERENCE HERE...BUT WILL NOT RULE IT OUT EITHER. RECENT
GFS RUNS HAVE BEEN FAST AND UNDER-DEVELOPED.


...TROUGH CROSSING THE NORTHWEST AND REACHING THE NORTHERN PLAINS
THU/FRI...

PREFERENCE: BLEND OF 12Z ECMWF/UKMET

THE MODELS PREDICT SIMILAR STRENGTH AND TIMING FOR THIS
PROGRESSIVE SHORTER WAVELENGTH SYSTEM. THEY DIFFER MAINLY IN THE
LATITUDE AT WHICH THE EMBEDDED VORTICITY MAXIMUM WILL FORM. THE
GFS/ECMWF/UKMET ARE IN THE MIDDLE...AND ARE SUPPORTED BY ENSEMBLE
INFORMATION...ALTHOUGH THE GFS APPEARS SOMEWHAT SLOW. THIS MAY BE
IN PART RELATED TO ITS DEEPER SOLUTION DOWNSTREAM OVER THE GREAT
LAKES WHICH PROPS UP SHORTWAVE RIDGING FARTHER WEST ACROSS THE
PLAINS ON THU/FRI.


...SYSTEM ENTERING THE SOUTHWEST U.S...

PREFERENCE: BLEND OF 00Z NAM/GFS WITH 12Z ECMWF

IT IS DIFFICULT TO JUDGE THIS SYSTEM AT 500 MB...GIVEN THE BROAD
WAVELENGTH AND WEAK GRADIENT. GENERALLY...THE 12Z UKMET APPEARS
FAST AND THE 12Z CANADIAN IS ONE OF THE DEEPEST SOLUTIONS. THE
NAM/GFS/ECMWF CLUSTER REASONABLY WELL AT 500 MB...WITH PLENTY OF
ENSEMBLE SUPPORT...AND THEIR DIFFERENCES FROM THE SURFACE TO 700
MB ARE EVEN LESS.


...PACIFIC NORTHWEST LATE FRIDAY...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE 12Z
CANADIAN

THE IMPACTS FROM THIS SYSTEM WILL LIKELY HOLD OFF UNTIL DAY 4.
THROUGH DAY 3 THERE IS STRONG MODEL AGREEMENT ON THE LARGE SCALE.
THE 12Z CANADIAN TRACKED THE ASSOCIATED SURFACE SYSTEM FARTHER
NORTH IN THE GULF OF ALASKA.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$





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