Prognostic Meteorological Discussion
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FXUS10 KWNH 240637
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 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/GFS/UKMET/GEM AND ECMWF


...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 AND
00Z GEFS MEAN BOTH SUPPORT THE GLOBAL MODEL CONSENSUS WITH THE
THIS FEATURE ALOFT. HOWEVER...AFTER ABOUT 72 HOURS...THE 00Z 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 WITH A GENERAL MODEL
COMPROMISE PRIOR TO THIS.


...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 00Z 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 00Z GEM BEGINS 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 00Z ECMWF
PUT MORE EMPHASIS ON THE LEAD WAVE SUN AS IT MOVES AWAY FROM THE
EAST COAST...BUT THE 00Z GEM/00Z UKMET AND 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 00Z 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: NON-GEM CONSENSUS
CONFIDENCE: AVERAGE

THE DEEP CLOSED LOW OVER NEW ENGLAND BEGINS TO GRADUALLY PIVOT
EAST OFFSHORE NOVA SCOTIA ON SAT BUT THEN BECOMES NOTABLY
ELONGATED BY SUN AS ADDITIONAL ENERGY DROPS SOUTH DOWN ACROSS THE
GREAT LAKES REGION. THE 00Z GEM IS NOW OVERALL THE WEAKEST
SOLUTION WITH THE EVOLUTION OF THE ELONGATED CLOSED LOW...AND BY
EARLY MON IS SLOWER TO PIVOT ENERGY SOUTHWARD THROUGH THE LOWER
GREAT LAKES REGION. THE 00Z GFS/00Z NAM/00Z UKMET AND 00Z ECMWF
ARE ALL BETTER CLUSTERED WITH DEPTH AND TIMING...AND SO A NON-GEM
CONSENSUS WILL BE PREFERRED WHICH IS ALSO SUPPORTED BY THE LATEST
GEFS MEAN AND ECENS MEAN.


...TROUGH/FRONT FOCUSED ACROSS THE NORTHERN HIGH PLAINS SUN AND
MON...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS INDICATE A NORTHERN STREAM TROUGH LINGERING OVER THE
NORTHERN ROCKIES EARLY SUN AND ADVANCING GRADUALLY EAST INTO THE
NORTHERN PLAINS ON MON. THIS ENERGY WILL BE ACCOMPANIED BY A FRONT
AND AN AREA OF LOW PRESSURE THAT SHOULD GRADUALLY WEAKEN BY MON.
MODEL SPREAD FOR MASS FIELDS IS RATHER MINIMAL...AND SO A GENERAL
MODEL COMPROMISE WILL BE PREFERRED HERE.


...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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