Prognostic Meteorological Discussion
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FXUS10 KWNH 161651
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1150 AM EST TUE DEC 16 2014

VALID DEC 16/1200 UTC THRU DEC 20/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...TROUGH DEVELOPING TOWARD THE SOUTHERN ROCKIES/PLAINS...

PREFERENCE: BLEND OF 00Z ECMWF AND 00Z ECENS MEAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE STILL ATTEMPTING TO CONVERGE TOWARD A COMMON
SOLUTION WHICH IS GENERALLY TOWARD THE NOTABLY MORE STABLE ECENS
MEAN. THE 12Z NAM IS A LITTLE SLOWER AND DEEPER THAN THE ECENS
MEAN...WITH THE 12Z GFS ALSO A LITTLE SLOWER BUT WEAKER. THE 00Z
GEM/00Z UKMET AND 00Z ECMWF ARE REASONABLY CLOSE IN DEPTH TO THE
00Z ECENS MEAN. AT THE SURFACE...THE HEIGHT FALLS SHOULD BEGIN TO
INVIGORATE A WAVE OF LOW PRESSURE OVER THE WESTERN GULF COAST
STATES. THE 00Z ECMWF AND 00Z ECENS MEAN ARE VERY WELL CLUSTERED
TOGETHER WITH TIMING AND STRENGTH. THE 12Z GFS IS CLOSE TO THE
ECMWF/ECENS MEAN CAMP...WITH THE 12Z NAM SLOWER. THE 00Z GEM AND
00Z UKMET ARE FASTER AND FLATTER. THE STRONGER MODEL CLUSTERING
RIGHT NOW FAVORS THE ECMWF/ECENS MEAN WHICH HAVE BEEN MUCH MORE
CONSISTENT THAN THE GFS/NAM SOLUTIONS...AND GIVEN THE SPREAD OF
SOLUTIONS...A BLEND OF THE ECMWF AND ECENS MEAN WILL BE FAVORED.


...SOUTHERN/CENTRAL PLAINS LEAD SHORTWAVE...

PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

AHEAD OF THE DEEPENING SOUTHERN ROCKIES/PLAINS SYSTEM A LEAD
SHORTWAVE WILL EJECT EAST ON WED/THU ACROSS THE CENTRAL/SOUTHERN
PLAINS BEFORE THEN SHEARING OUT INTO AN UPPER LEVEL CONFLUENCE
ZONE OVER THE OH VALLEY ON FRI. THE 00Z GEM IS THE FLATTEST
SOLUTION WITH THIS FEATURE...BUT THE REMAINING MODELS UNIFORMLY
MAINTAIN A WEAK REFLECTION OF THIS WAVE EVEN INTO THE OH VALLEY.
BASED ON BETTER RUN TO RUN CONTINUITY AND PREFERENCE WITH THE
LARGER SCALE PATTERN...THE ECMWF WILL BE PREFERRED.


...MIDWEST/GREAT LAKES/NORTHEAST...

PREFERENCE: BLEND OF 12Z GFS/00Z GEM AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE MODELS CONTINUE TO SUGGEST A CYCLONE LIFTING INTO THE GREAT
LAKES WHICH WILL THEN MERGE WITH A DEEPER LOW CENTER DROPPING DOWN
FROM ONTARIO. FOLLOWING THIS MERGER...THE MODELS AGREE IN TAKING
AN UPPER LOW PROGRESSIVELY DOWNSTREAM ACROSS THE NORTHEAST ON WED
AND INTO NOVA SCOTIA BY THURS. ONE SURFACE LOW CENTER MOVING
ACROSS THE LOWER GREAT LAKES REGION WILL GRADUALLY GIVE WAY TO A
SECONDARY LOW THAT DEVELOPS BY WED MORNING SOUTH OF LONG ISLAND
AND LIFTS NORTHEAST THROUGH THE GULF OF MAINE BEFORE ARRIVING IN
NOVA SCOTIA BY THURS. THE 12Z NAM IS A BIT SLOWER AND TO THE LEFT
OF THE MULTI-MODEL CONSENSUS WITH THE LOW TRACK. THE 00Z UKMET ON
THE FLIP SIDE IS TO THE RIGHT OF THE SAME CONSENSUS. THE 12Z
GFS/00Z ECMWF AND 00Z GEM CLUSTER TOGETHER VERY WELL IN THE
MIDDLE...AND THIS CONSENSUS WILL BE PREFERRED.


...PACIFIC NORTHWEST...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODELS ARE CONVERGING ON THE PRESENCE OF A DEEP LOW IN THE GULF OF
ALASKA...WITH AN ATTENDANT JET DIVING TOWARD THE WA/OR COAST. THE
STRONGER MODEL CLUSTERING FOR THE PACIFIC NORTHWEST SUGGESTS
LEANING TOWARD A BLEND OF THE 12Z GFS AND 00Z ECMWF. THE 00Z GEM
AND TO AN EXTENT THE 00Z UKMET ARE SEEN AS DRIVING ENERGY INLAND
FASTER AND SHARPER THAN THE GFS/ECMWF CAMP. THE 12Z NAM APPEARS TO
BE A LITTLE TOO SLOW. A BLEND OF THE 12Z GFS AND 00Z ECMWF WILL BE
FAVORED FOR THE PACIFIC NORTHWEST THIS PERIOD.


...NORTHERN ROCKIES/NORTHERN PLAINS...

PREFERENCE: BLEND OF 12Z GFS/00Z UKMET AND 00Z GEM
CONFIDENCE: AVERAGE

SEVERAL SMALLER SCALE AND RELATIVELY WEAK VORTICITY MAXIMA WILL
INTERACT WITHIN A GENERAL WEAKNESS IN THE MID LEVEL HEIGHT FIELD
OVER THE NORTHERN ROCKIES/PLAINS. BY EARLY FRI...SOME
CONSOLIDATION OF THIS ENERGY SHOULD OCCUR DOWNSTREAM OF A
SHARPENING SHORTWAVE RIDGE
AXIS...YIELDING A LOOSELY DEFINED TROUGH OVER EASTERN MT/WY AND
INTO THE CENTRAL AND NORTHERN PLAINS. THE 00Z ECMWF STILL TEND TO
BE A LITTLE WEAKER THAN THE MULTI-MODEL CONSENSUS. WILL MAINTAIN
CONTINUITY AND CONTINUE FAVORING A BLEND OF THE GFS/UKMET AND GEM
WHICH WHICH ARE PRETTY WELL CLUSTERED TOGETHER.

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

ORRISON

$$





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