Prognostic Meteorological Discussion
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593
FXUS10 KWNH 280632
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 AM EDT THU APR 28 2016

VALID APR 28/0000 UTC THRU MAY 01/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/ECMWF/UKMET/CMC AND
FINAL MODEL PREFERENCES


...LOW PRESSURE SYSTEM OVER THE CENTRAL PLAINS/MIDWEST MOVING TO
THE MID-ATLANTIC BY FRIDAY...

PREFERENCE: ECMWF
CONFIDENCE: ABOVE AVERAGE

THE UPPER-LEVEL LOW OVER THE CENTRAL PLAINS/MIDWEST TONIGHT IS
FORECAST BY ALL MODELS TO OPEN INTO A WEAKER SHORTWAVE AS IT MOVES
EAST ACROSS THE GREAT LAKES TO THE MID-ATLANTIC STATES BY FRIDAY.
THE OCCLUDED SURFACE LOW WILL WEAKEN OVER THE OHIO VALLEY WHILE A
NEW SURFACE LOW DEVELOPS OVER THE CAROLINAS AND MOVES INTO THE
ATLANTIC OCEAN. THE GFS KEEPS THE SHORTWAVE STRONGER (AND SLOWER)
AS IT CROSSES THE GREAT LAKES RELATIVE TO OTHER DETERMINISTIC AND
ENSEMBLE GUIDANCE. AT THE SURFACE...THE GFS SEEMS TO BE MORE
SIMILAR TO OTHER GUIDANCE...AND IS WELL WITHIN CONSENSUS AS THE
NEW SURFACE LOW DEVELOPS OVER THE NORTH CAROLINA THURSDAY AND
MOVES NORTHEAST INTO THE ATLANTIC. HOWEVER...GIVEN THE ISSUES WITH
THE GFS WITH THE AMPLITUDE OF THE UPPER TROUGH...PREFER THE ECMWF
WHICH HAS SUPPORT...TO VARYING DEGREES...FROM THE OTHER NON-GFS
DETERMINISTIC AND ENSEMBLE GUIDANCE.


...LOW PRESSURE SYSTEM CROSSING THE SOUTHWESTERN U.S. ON THURSDAY
AND EMERGING INTO THE SOUTHERN PLAINS ON FRIDAY...

PREFERENCE: GFS/ECMWF COMPROMISE THROUGH 00Z SUNDAY
            ECMWF/GEFS MEAN BLEND AFTER 00Z SUNDAY
CONFIDENCE: AVERAGE

THE NAM AND GFS ARE COMPARABLE TO THE MODEL CONSENSUS WITH RESPECT
TO THIS FEATURE THROUGH THURSDAY NIGHT. AS THE SURFACE LOW EMERGES
INTO THE SOUTHERN PLAINS ON FRIDAY...THE NAM BECOMES A LITTLE
FASTER THAN CONSENSUS WITH THE UPPER-LEVEL TROUGH AND WITH THE
SURFACE LOW. THE GFS LOOKS SIMILAR TO CONSENSUS AT THE
UPPER-LEVELS...BUT ITS SURFACE LOW LAGS A LITTLE SLOWER THAN
CONSENSUS (IT DOES HAVE THE SUPPORT OF ITS ENSEMBLE MEAN HOWEVER).
THROUGH SUNDAY...WILL RECOMMEND A COMPROMISE BETWEEN THE  ECMWF
(WHICH IS A LITTLE FASTER THAN ITS ENSEMBLE MEAN) AND THE SLOWER
GFS. STARTING SUNDAY AFTERNOON...THE GFS BEGINS TO WEAKEN THE
UPPER-LEVEL WAVE A LITTLE MORE QUICKLY THAN CONSENSUS... AND THUS
SHUNTS THE SURFACE LOW EAST INTO THE OHIO VALLEY A LITTLE MORE
QUICKLY. THE 00Z GEFS MEAN CONTINUES TO SUPPORT THE SLOWER
ECMWF/UKMET/NAM/CMC SOLUTION BY SUNDAY MORNING. AS A RESULT...WILL
RECOMMEND THE ECMWF ALONG WITH THE GEFS MEAN AFTER 00Z SUNDAY.


...UPPER-LEVEL TROUGH/PACIFIC COLD FRONT REACHING THE NORTHWEST
THURSDAY NIGHT...
...CLOSED UPPER-LEVEL LOW OVER THE SOUTHWEST ON SATURDAY...

PREFERENCE: GFS/NAM/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GFS IS INITIALLY A LITTLE FASTER THAN CONSENSUS WITH BRINGING
THE UPPER TROUGH INTO THE PACIFIC NORTHWEST ON FRIDAY...WHILE THE
NAM IS WELL WITHIN THE MIDDLE OF CONSENSUS. BY THE TIME THE TROUGH
BEGINS TO CLOSE OFF INTO AN UPPER LOW OVER THE SOUTHWESTERN U.S.
ON SATURDAY THE NAM AND GFS ARE BOTH WELL WITHIN A REASONABLE
RANGE OF CONSENSUS THAT INCLUDES THE ECMWF/12Z ECMWF ENSEMBLE
MEAN/00Z GEFS MEAN. THE UKMET SEEMS TO BE ON THE FAST SIDE OF THE
SPREAD WITH THE PROGRESSION OF THE UPPER LOW WHILE THE CMC IS ON
THE SLOW SIDE. GIVEN THE SIMILAR SOLUTIONS SHOWN BY THE
GFS/NAM/ECMWF...WILL RECOMMEND A BLEND OF THESE THREE SOLUTIONS AT
THIS TIME.


...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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