Prognostic Meteorological Discussion
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000
FXUS10 KWNH 311854
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 PM EDT FRI OCT 31 2014

VALID OCT 31/1200 UTC THRU NOV 04/0000 UTC

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...TROUGH AFFECTING THE EASTERN U.S...

PREFERENCE: BLEND OF 12Z NAM/ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GFS...NAM...ECMWF...AND UKMET CLUSTER FAIRLY WELL. ENSEMBLE
SPREAD IS AVERAGE OR BORDERING ON LESS THAN AVERAGE. YET SUBTLE
VARIATION IN THE HANDLING OF COASTAL LOW PRESSURE MAKES A LARGE
DIFFERENCE FOR SOME AREAS...PARTICULARLY MAINE. THE GFS HAS
CONSISTENTLY OFFERED MORE AGGRESSIVE SOLUTIONS IN WHICH THE
DEEPENING CYCLONE TRACKS CLOSER TO THE NEW ENGLAND
COAST...YIELDING A GREATER EXPANSE OF MODERATE OR HEAVY
PRECIPITATION INLAND. THE OPERATIONAL GFS CONTINUES A LITTLE LEFT
OF THE GEFS MEAN. THE UKMET...MEANWHILE...TRENDED INTO A TIGHTER
CONSENSUS WITH THE NAM/ECMWF MASS FIELDS...ALTHOUGH THE UKMET
PRECIPITATION TRENDED MORE TOWARD THE WETTER GFS. THE UKMET TENDS
TO HAVE A HIGH BIAS...SO WE WILL MAINTAIN A RECOMMENDATION OF THE
MORE CONSISTENT NAM/ECMWF. THE LOBE OF COLD AIR THAT SLIDES INTO
THE SOUTHEAST U.S. BEHIND THIS SYSTEM IS IMPRESSIVE WITH 850 MB
TEMPERATURES 0 TO -5 C...OR 3 TO 4 DEVIATIONS BELOW CLIMATOLOGY.


...TROUGH MIGRATING THROUGH THE WESTERN AND CENTRAL U.S...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE 12Z
CANADIAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODELS HAVE BEEN CONSISTENT IN DEPICTING A POSITIVELY TILTED LARGE
SCALE TROUGH WITH A WELL DEFINED LEAD WAVE EJECTING TO THE
NORTHERN PLAINS AND A SEPARATE VORTICITY MAXIMUM PASSING THROUGH
THE SOUTHWEST U.S. THE LEAD WAVE HAS A BETTER DEFINED SURFACE
REFLECTION. AS WAS TRUE FOR THE EASTERN U.S. SYSTEM...THE
GFS/NAM/ECMWF/UKMET CLUSTER FAIRLY WELL. THERE ARE VARIATIONS IN
THE FORWARD SPEED OF THE NORTHERN AND SOUTHERN STREAM WAVES
ALOFT...BUT DIFFERENCES AT THE SURFACE ARE LESS. ALOFT THE ECMWF
WOULD BE PREFERRED UP NORTH...AND THE NAM/GFS/UKMET WOULD BE
FAVORED IN THE SOUTHWEST/SOUTHERN PLAINS. DIFFERENCES ARE SMALL
ENOUGH TO MAKE A MORE GENERAL RECOMMENDATION OF A MULTI-MODEL
BLEND. THE CANADIAN IS OMITTED ONLY BECAUSE IT IS SLOW TO MOVE THE
SURFACE LOW IN THE NORTHERN PLAINS/SOUTHERN CANADA.


...NEXT SYSTEM INTO THE PACIFIC NORTHWEST SUN/MON...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE HANDLING THE PATTERN WELL GIVEN THE EXISTENCE OF
LARGE SCALE...EVENLY SPACED WAVES AND LITTLE IN THE WAY OF SPLIT
FLOW. THE MOST NOTABLE OUTLIER WAS THE 00Z CANADIAN WHICH
UNDER-EMPHASIZED SHORTWAVE RIDGING POPPING UP INTO SOUTHWEST
CANADA ON MONDAY. THE 12Z RUN IMPROVED...FORMING A STRONG
CONSENSUS AND GIVING US SOMEWHAT GREATER CONFIDENCE THAN AVERAGE
FOR A DAY 3 FORECAST.

...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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