Prognostic Meteorological Discussion
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FXUS10 KWNH 281610
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1109 AM EST SUN DEC 28 2014

VALID DEC 28/1200 UTC THRU JAN 01/0000 UTC

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

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


...SHORTWAVE ENERGY SHEARING FROM THE SOUTHERN PLAINS TO THE TN
VALLEY/SOUTHEAST...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

SHORTWAVE ENERGY CURRENTLY OVER THE SOUTHERN PLAINS WILL SHEAR
EAST OUT OVER THE NEXT COUPLE OF DAYS DOWNSTREAM ACROSS THE TN
VALLEY AND SOUTHEAST. A WEAK SURFACE LOW SHOULD CROSS THE INTERIOR
SOUTHEAST AND SOUTHERN MID-ATLANTIC LATER TONIGHT AND MON BEFORE
GOING OFFSHORE. THERE IS MINIMAL MASS FIELD SPREAD WITH THIS SYS
NOW...AND SO A GENERAL MODEL COMPROMISE WILL BE FAVORED.


...PROGRESSIVE SHORTWAVE IMPULSE REACHING THE OH
VALLEY/MID-ATLANTIC ON TUES...

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

A SHORTWAVE DIGGING ACROSS THE GREAT BASIN CURRENTLY WILL ADVANCE
RAPIDLY EAST ACROSS THE CENTRAL PLAINS ON MON...AND THEN EAST
ACROSS THE OH VALLEY AND MID-ATLANTIC REGION ON TUES. THE 12Z NAM
AND THE 09Z SREF ARE STRONGER OUTLIERS SOLNS AS COMPARED TO THE
12Z GFS AND ALL OF THE NON-NCEP MODELS INCLUDING THE 00Z UKMET/00Z
GEM AND 00Z ECMWF. THE PREFERENCE AS SUPPORTED BY THE LATEST GEFS
MEAN AND ECENS MEAN IS FOR A FLATTER SHORTWAVE TO MOVE
PARTICULARLY ACROSS THE OH VALLEY AND MID-ATLANTIC CONSIDERING THE
LARGER SCALE CONFLUENT MID LEVEL FLOW THAT THE ENERGY WILL
ENCOUNTER. WILL LEAN TOWARD A BLEND OF THE 12Z GFS AND 00Z ECMWF.


...JET ENERGY/DEEP TROUGH EVOLVING OVER THE WESTERN U.S THROUGH
WED...
...CLOSED LOW OVER THE SOUTHWEST BY WED...

PREFERENCE: BLEND OF THE 00Z ECMWF/00Z ECENS MEAN AND 06Z GEFS MEAN
CONFIDENCE: AVERAGE

THE MODELS CONTINUE TO ADVERTISE A STRONG UPPER RIDGE DEVELOPING
OFFSHORE THE WEST COAST AND NEAR PORTIONS OF THE GULF OF AK. THIS
WILL ALLOW A SIGNIFICANT AMOUNT OF SHORTWAVE/JET ENERGY TO DIVE
SOUTH DOWN THE EAST SIDE OF THE RIDGE AND INTO THE WESTERN U.S.
THROUGH THE PERIOD. THE RESULT WILL GRADUALLY BE A DEEP TROUGH
SINKING SOUTH THROUGH THE GREAT BASIN...WITH ULTIMATELY AN
ELONGATED CLOSED UPPER LOW DEVELOPING OVER CA/NV THAT WILL BE
SETTLING INTO THE SOUTHWEST U.S. BY LATE WED. THE 12Z NAM
GRADUALLY BECOMES A SOMEWHAT SLOWER AND DEEPER OUTLIER WITH THE
CLOSED LOW EVOLUTION. THE 00Z UKMET IS THE FASTEST SOLN AND DRIVES
HEIGHT FALLS MORE QUICKLY INTO THE SOUTHWEST BY WED. THE 12Z
GFS/00Z ECMWF AND 00Z GEM SPLIT THE DIFF BUT THE GEM IS TENDING
TOWARD THE FASTER UKMET BY THE END OF THE PERIOD AND GRADUALLY THE
GFS ENDS UP NOTABLY SOUTH OF THE ECMWF. THE 00Z ECMWF HAS THE
STRONGEST ENSEMBLE SUPPORT INCLUDING BOTH THE GEFS MEAN AND ECENS
MEAN...AND SO THIS CONSENSUS WILL BE PREFERRED.


...NORTHERN STREAM SHORTWAVE TROUGH DROPPING ACROSS THE UPPER
MIDWEST BY TUES...

PREFERENCE: 12Z GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS INDICATE A NORTHERN STREAM TROUGH DIGGING SOUTH FROM
CANADA AND TRAVERSING THE UPPER MIDWEST BY TUESDAY AND THEN ACROSS
THE OH VALLEY AND LOWER GREAT LAKES ON WED. THE 00Z ECMWF IS THE
MOST PROGRESSIVE SOLN...FOLLOWED BY THE 12Z GFS. THE 12Z NAM/00Z
UKMET AND 00Z GEM ARE ALL A LITTLE SLOWER. THE 12Z GFS APPEARS TO
BE A REASONABLE COMPROMISE SOLN WITH RESPECT TO TIMING.
FORTUNATELY THERE IS MINIMAL SPREAD WITH RESPECT TO SHORTWAVE
DEPTH.

...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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