Prognostic Meteorological Discussion
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000
FXUS10 KWNH 290649
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 AM EST MON DEC 29 2014

VALID DEC 29/0000 UTC THRU JAN 01/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...PROGRESSIVE SHORTWAVE MOVING FROM THE ARKLATEX TOWARD THE
MID-ATLANTIC...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

EMBEDDED WITHIN SOUTHWESTERLY ALOFT...AN IMPULSE ORIGINATING OVER
THE ARKLATEX WILL GRADUALLY SHEAR WHILE LIFTING INTO THE
MID-ATLANTIC BY 29/1200Z. MODELS ARE IN SUFFICIENT AGREEMENT WITH
THIS WAVE ALONG WITH THE POSITION OF THE BOUNDARY MOVING INTO THE
OFFSHORE WATERS. A GENERAL MODEL COMPROMISE WILL BE RECOMMENDED.


...MID-LEVEL ENERGY TRACKING THROUGH THE CENTRAL PLAINS ON
30/0000Z...

FINAL PREFERENCE: NON-21Z SREF MEAN MODEL CONSENSUS
FORECAST CONFIDENCE: ABOVE AVERAGE

HEIGHT FALLS CURRENTLY MOVING THROUGH THE CENTRAL GREAT BASIN WILL
HELP CARVE OUT AN ELONGATED AXIS OF VORTICITY INTO THE CENTRAL
HIGH PLAINS BY MONDAY EVENING. THE SYSTEM SHOULD BECOME RATHER
PROGRESSIVE AS IT MOVES EAST OF THE GREAT PLAINS REACHING THE
CENTRAL APPALACHIANS/MID-ATLANTIC BY 30/1800Z. THE GUIDANCE IS IN
MUCH BETTER AGREEMENT THAN PREVIOUS DAYS AS THE SPREAD HAS
DIMINISHED MARKEDLY. THE 21Z SREF MEAN IS PERHAPS A BIT FARTHER
NORTH WITH THE SHORTWAVE ENERGY SO WILL GO WITH A NON-21Z SREF
MEAN MODEL CONSENSUS.


...CLOSED LOW ANCHORING THE SOUTHWESTERN U.S. TUESDAY THROUGH
THURSDAY...
...ACCOMPANYING SURGE OF ARCTIC AIR...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A HIGH AMPLITUDE PATTERN IS IN PLACE TO START THE PERIOD WITH A
STOUT UPPER RIDGE EXTENDING ALONG THE EAST PACIFIC UP TO THE YUKON
TERRITORY. STRONG HEIGHT FALLS ASSOCIATED WITH A VIGOROUS
SHORTWAVE WILL DIVE DOWN ACROSS THE WESTERN U.S. BEFORE SETTLING
INTO THE DESERT SOUTHWEST BY TUESDAY. THE FORECAST SPREAD IS NOT
TOO SIGNIFICANT THROUGH EARLY WEDNESDAY WITH SOLUTIONS IN THE
BALLPARK OF ONE ANOTHER. TIMING DIFFERENCES EMERGE BY MID-WEEK
ONWARD AS THE UPPER LOW SPINS OVER SOUTHERN CA BEFORE SHIFTING
EASTWARD. THE 12Z ECMWF ENSEMBLE MEAN IS SLOWER THAN THE 00Z GEFS
MEAN WHILE THE 21Z SREF IS DISPLACED TO THE NORTH. REGARDING MODEL
TRENDS...THE 00Z CMC/ECMWF MOVED IN THE SOMEWHAT FASTER DIRECTION
WHILE THE 00Z UKMET HAS GENERALLY MAINTAINED ITS CONTINUITY. THIS
SHIFT IN THE ECMWF DOES KEEP IT WELL WITHIN THE SPREAD IN THE
540-DM SPAGHETTI PLOTS. WPC WILL KEEP THE PREVIOUS PREFERENCE AS
IS WHICH FEATURES A BLEND OF THE 00Z GFS/ECMWF.


...SERIES OF NORTHERN STREAM WAVES CROSSING THE GREAT LAKES
REGION...

FINAL PREFERENCE: MODEL COMPROMISE BETWEEN THE 00Z GFS/ECMWF/UKMET
THROUGH DAY 2...THEREAFTER A BLEND OF THE 00Z GEFS/12Z ECMWF
ENSEMBLE MEANS
FORECAST CONFIDENCE: AVERAGE

AN ACTIVE NORTHERN STREAM WILL DRAW A SERIES OF IMPULSES FROM THE
UPPER MIDWEST ACROSS THE GREAT LAKES FROM TUESDAY THROUGH
THURSDAY. REGARDING THE FIRST SYSTEM CROSSING THE UPPER GREAT
LAKES ON 31/0000Z...THE 21Z SREF MEAN IS SLOWER/MORE NORTHWARD.
THERE IS MORE UNCERTAINTY WITH THE NEXT DISTURBANCE SLIDING INTO
MN BY WEDNESDAY. THE BIGGEST OUTLIERS ARE THE 00Z NAM/CMC WHICH
FEATURE NOTHING CLOSE TO WHAT THE ENSEMBLE MEANS AND OTHER
DETERMINISTIC GUIDANCE SHOW. THEREAFTER...A THIRD IMPULSE WILL
BEGIN TO CROSS INTO CENTRAL CANADA WITH A SLEW OF DIFFERENCES
NOTED WITH THAT FEATURE. WILL FOLLOW A BLEND OF THE ENSEMBLE MEANS
FOR DAY 3 IN THAT CASE. BEFORE THAT...A MODEL COMPROMISE BETWEEN
THE 00Z GFS/ECMWF/UKMET IS FEASIBLE.


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

RUBIN-OSTER

$$





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