Prognostic Meteorological Discussion
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000
FXUS10 KWNH 240429
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1228 AM EDT FRI APR 24 2015

VALID APR 24/0000 UTC THRU APR 27/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...DEEP TROUGH/CLOSED LOW DIGGING INTO SOUTHWEST U.S. THIS
WEEKEND...
...LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON...

PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 72 HOURS
            NON-GFS CONSENSUS...AFTER 72 HOURS
CONFIDENCE: ABOVE AVERAGE

THE MODELS HANDLE THE EVOLUTION OF THIS DIGGING SYSTEM SIMILARLY
THROUGH THE PERIOD UNTIL ABOUT 72 HOURS. THE 12Z ECENS MEAN IS
MUCH MORE SUPPORTIVE OF THE GLOBAL MODEL CONSENSUS OVERALL...WITH
THE 18Z GEFS MEAN LIKELY TOO PROGRESSIVE AND FOCUSING TOO MUCH
ENERGY FARTHER EAST ACROSS THE SOUTHERN PLAINS BY MON. THE 00Z GFS
ALOFT APPEARS REASONABLE THROUGH THE PERIOD...ALTHOUGH AFTER 72
HOURS THE GFS HANGS ON TO A MUCH BETTER DEFINED SURFACE LOW OVER
NORTH TEXAS. THE MULTI-MODEL CONSENSUS SUGGESTS LOW PRESSURE
SHOULD DROP SOUTHEAST DOWN THROUGH THE SOUTHERN HIGH PLAINS AND
FOCUS DOWN TOWARD FAR SOUTH TX NEAR THE GULF COAST BY MON. A
NON-GFS CONSENSUS WILL BE PREFERRED AFTER 72 HOURS.


...SOUTHERN STREAM SHORTWAVE TRAVELING FROM THE HIGH PLAINS TO THE
MID ATLANTIC...
...ASSOCIATED SURFACE PATTERN ALONG THE EAST COAST...

PREFERENCE: BLEND OF 00Z NAM AND 12Z ECMWF
CONFIDENCE: AVERAGE

THE MID LEVEL TROUGH/CLOSED LOW CURRENTLY OVER THE SOUTHWEST WILL
ADVANCE PROGRESSIVELY DOWNSTREAM...REACHING THE PLAINS FRI AND THE
EAST COAST BY SUN MORNING WHILE GRADUALLY SHEARING OUT. THERE IS
GENERALLY GOOD MASS FIELD AGREEMENT AMONG THE DETERMINISTIC MODELS
AT LEAST THROUGH ABOUT 48 HOURS WHEN THE 12Z GEM AND THE 12Z UKMET
BEGIN TO EDGE SLOWER THAN THE MULTI-MODEL CONSENSUS. ALL OF THE
MODELS DEPICT SURFACE LOW PRESSURE THAT WILL ADVANCE EAST FROM THE
CENTRAL PLAINS FRI TO THE MID-ATLANTIC COAST BY EARLY SUN.
HOWEVER...BY SAT THERE IS DECENT AGREEMENT THAT MULTIPLE LOW
CENTERS WILL BE IMPACTING THE MID-ATLANTIC REGION. MOST OF THE
MODELS HAVE A LEAD WAVE THAT DEVELOPS OVER THE MID-ATLANTIC
COASTAL PLAIN BY LATE SAT THAT MOVES OFFSHORE EARLY SUN.
MEANWHILE...THE MAIN LOW ASSOCIATED WITH THE SHEARING SHORTWAVE
WILL STILL BE OVER THE OH VALLEY APPROACHING THE CENTRAL
APPALACHIANS. THE 00Z NAM AND 12Z ECMWF PUT MORE EMPHASIS ON THE
LEAD WAVE SUN AS IT MOVES AWAY FROM THE EAST COAST...BUT THE 12Z
GEM/12Z UKMET AND ESPECIALLY THE 00Z GFS ALL FAVOR THE SLOWER WAVE
TIED IN WITH THE SHORTWAVE. IN FACT...THE GFS SAYS THIS WAVE
REMAINS THE DOMINANT WAVE THROUGH MON. THE 18Z GEFS MEAN AND 12Z
ECENS MEAN HOWEVER FAVOR A MORE PROGRESSIVE SCENARIO WITH A LEAD
WAVE ON THE MID-ATLANTIC COAST EARLY SUN BECOMING THE DOMINANT
WAVE. THIS IS IN SUPPORT OF THE ECMWF AND NAM...AND SUGGESTS THAT
THE GFS IN PARTICULAR IS AN OUTLIER AFTER ABOUT 60 HOURS. A BLEND
OF THE ECMWF AND NAM WILL BE PREFERRED GIVEN THE STRONGER ENSEMBLE
SUPPORT.


...DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND AND THE EASTERN
GREAT LAKES...

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

THE DEEP CLOSED LOW OVER NEW ENGLAND BEGINS TO GRADUALLY PIVOT
EAST OFFSHORE NOVA SCOTIA ON SAT BUT THEN BECOMES NOTABLY
ELONGATED BU SUN AS ADDITIONAL ENERGY DROPS SOUTH DOWN ACROSS THE
GREAT LAKES REGION. THE 12Z GEM AND 12Z UKMET REDEVELOP A SEPARATE
CLOSED LOW OVER THE LOWER LAKES REGION AND INTO NY STATE BY SUN
NIGHT. THE 00Z GFS/00Z NAM AND 12Z ECMWF ARE LESS EMPHATIC AND
HAVE MORE OF AN ELONGATED APPEARANCE...WITH MORE ENERGY FOCUSED
NEAR THE GULF OF MAINE SUN NIGHT AND MON. THE NAM/GFS AND ECMWF
HAVE MUCH BETTER ENSEMBLE SUPPORT FROM THE LATEST GEFS MEAN AND
ECENS MEAN...AND SO A CONSENSUS OF THESE SOLUTIONS WILL BE
PREFERRED.


...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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