Prognostic Meteorological Discussion
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FXUS10 KWNH 020453
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1252 AM EDT MON MAY 02 2016

VALID MAY 02/0000 UTC THRU MAY 05/1200 UTC

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

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

...SHORTWAVES MOVING FROM THE OHIO VALLEY TO THE NORTHEAST ON
MONDAY...
...SURFACE LOWS ACROSS THE NORTHEAST/MID-ATLANTIC ON MONDAY...

PRELIMINARY PREFERENCE: 12Z ECMWF/NAM BLEND
CONFIDENCE: AVERAGE

A BROAD MID/UPPER-LEVEL TROUGH WILL EXPAND OVER THE EASTERN HALF
OF THE NATION MONDAY INTO TUESDAY AS MULTIPLE SHORTWAVES PROGRESS
THE REGION. AT THE SURFACE...A FRONTAL BOUNDARY WITH MULTIPLE
WAVES OF LOW PRESSURE ALONG IT WILL AFFECT AREAS FROM THE
NORTHEAST TO THE LOWER MS VALLEY. MODELS INDICATE ONE SURFACE LOW
MOVING FROM THE OHIO VALLEY INTO THE NORTHEAST ON MONDAY WHILE A
SECOND SURFACE LOW DEVELOPS FARTHER SOUTH ALONG THE FRONT OVER THE
MID-ATLANTIC REGION. WITH THE SURFACE LOW CROSSING THE
NORTHEAST...THE GFS APPEARS TOO FAR EAST OFF THE NEW ENGLAND COAST
BY MONDAY NIGHT. THE NAM IS MORE IN LINE WITH THE LOW POSITION
SHOWN BY THE 12Z ECMWF/ECMWF ENS MEAN/UKMET/CMC. FOR THE SURFACE
LOW DEVELOPING OVER THE MID-ATLANTIC MONDAY AFTERNOON...THE GFS
AND NAM ARE GENERALLY IN GOOD AGREEMENT WITH THE MODEL CONSENSUS
AS THE LOW WEAKENS AND MOVES OFF THE COAST ON TUESDAY. THE
NORTHERN OF THE TWO SURFACE LOWS WILL BE MORE SIGNIFICANT PLAYER
IN THE WEATHER ACROSS NEW ENGLAND ON MONDAY...THEREFORE WILL
RECOMMEND A BLEND OF THE NAM AND 12Z ECMWF AT THIS TIME.


...SHORTWAVE ENTERING THE NORTHERN PLAINS/UPPER MIDWEST ON
MONDAY...
...COLD FRONT ACROSS THE LOWER MS VALLEY AND SOUTHEASTERN STATES...
...SURFACE LOW DEVELOPING ACROSS THE SOUTHERN MID-ATLANTIC ON
WEDNESDAY...

PRELIMINARY PREFERENCE: GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

A MORE SIGNIFICANT SHORTWAVE WILL ENTER THE NORTHERN PLAINS/UPPER
MIDWEST MONDAY MORNING BEFORE DIVING SOUTHEASTWARD AND DEEPENING
THE LONG WAVE TROUGH ON TUESDAY. THE NAM APPEARS TO BE A LITTLE TO
WEAK/FAST WITH THIS SHORTWAVE BY TUESDAY (AND WITH THE SURFACE
FRONT ACROSS THE SOUTHEAST)...WHILE THE GFS IS CLOSER IN-LINE WITH
THE CONSENSUS SOLUTION REPRESENTED BY THE 12Z ECMWF/CMC. AS THE
FRONT MOVES TOWARD THE EAST COAST...THIS SHORTWAVE WILL INFLUENCE
THE DEVELOPMENT OF AN ADDITIONAL WAVE OF LOW PRESSURE ALONG THE
SURFACE FRONT ACROSS THE SOUTHERN MID-ATLANTIC BY WEDNESDAY
MORNING...WHICH THEN MOVES NORTHEASTWARD OFFSHORE. MODELS ARE
INITIALLY IN GOOD AGREEMENT ON THE DEVELOPMENT OF THE LOW BUT
SPREAD INCREASES QUICKLY AFTER THE LOW MOVES OFFSHORE. THE NAM
APPEARS TO MOVE THE LOW NORTHEASTWARD MORE QUICKLY THAN
CONSENSUS...WHILE THE GFS/12Z UKMET/12Z CMC ARE SLOWER. A SOLUTION
SLOWER THAN THE NAM/12Z ECMWF IS ALSO SUPPORTED BY THE 12Z ECMWF
ENSEMBLE MEAN. A COMBINATION OF THE GFS AND 12Z ECMWF WOULD SEEM
TO BEST REPRESENT CONSENSUS AT THIS TIME.


...LOW PRESSURE ACROSS THE GREAT LAKES WED MORNING...

PRELIMINARY PREFERENCE: GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

A STRONG SHORTWAVE WILL DIVE SOUTHEASTWARD FROM THE WESTERN HUDSON
BAY TO UPPER GREAT LAKES BY TUESDAY MORNING BEFORE CLOSING OFF
INTO AN UPPER-LEVEL LOW. THE ACCOMPANYING SURFACE LOW PRESSURE
SYSTEM WILL BRING PRECIPITATION TO THE UPPER GREAT LAKES ON
TUESDAY. THE NAM AND GFS BOTH APPEAR ON THE DEEP SIDE WITH THE 500
HPA LOW...ALTHOUGH NOT TO THE POINT OF BEING OUTSIDE CONSENSUS. AT
THE SURFACE...THE GFS AND NAM ARE RELATIVELY CLOSE TO THE
CONSENSUS WITH THE TIMING OF THE COLD FRONT AS IT MOVES ACROSS THE
MIDWEST. AS THE LOW PRESSURE SYSTEM BEGINS TO INTERACT WITH THE
SYSTEM ALONG THE MID-ATLANTIC/NORTHEAST COASTLINE WED NIGHT/THURS
MORNING...IT IS UNCLEAR HOW STRONG GREAT LAKES SURFACE LOW WILL
REMAIN AS IT ENTERS THE LOWER GREAT LAKES. THE GFS WEAKENS THE
GREAT LAKES SFC LOW MORE QUICKLY THAN THE 12Z ECMWF...WHILE THE
ENSEMBLE MEANS ARE IN BETWEEN. THUS A GFS/12Z ECMWF BLEND APPEARS
REPRESENT THE BEST SOLUTION OVERALL.


...DEEP UPPER TROUGH APPROACHING THE WEST COAST ON TUES...
...CLOSED UPPER-LEVEL LOW OFF THE COAST OF CALIFORNIA WED
NIGHT/THURS...

PRELIMINARY PREFERENCE: GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE NAM AND GFS ARE BOTH WITHIN THE MODEL CONSENSUS WITH THE
TIMING AND AMPLITUDE OF THE MID/UPPER-LEVEL TROUGH AS IT
APPROACHES THE WEST COAST ON TUESDAY. AS THE SYSTEM CLOSES OFF
INTO A LOW AT 500 HPA BY WEDNESDAY...THE GFS REMAINS RELATIVELY
CLOSE TO THE 12Z ECMWF AND CONSENSUS...WHILE THE NAM APPEARS A
LITTLE MORE AMPLIFIED WITH THE TROUGH AS THE LOW CLOSES OFF. GIVEN
THAT THE 12Z ECMWF ENSEMBLE MEAN/18Z GEFS MEAN BOTH ARE SIMILAR TO
THE GFS/12Z ECMWF...WILL RECOMMEND A BLEND OF THESE TO MODELS AT
THIS POINT.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

RYAN

$$





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