Prognostic Meteorological Discussion
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FXUS10 KWNH 280430
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 AM EDT THU MAY 28 2015

VALID MAY 28/0000 UTC THRU MAY 31/1200 UTC

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

00Z NAM/GFS EVALUATION AND PRELIMINARY MODEL PREFERENCES

MODEL INITIALIZATION ERRORS DO NOT APPEAR TO BE SUFFICIENTLY LARGE
TO IMPACT THEIR FORECASTS OF LARGE-SCALE FEATURES.


...SHORTWAVE AND SURFACE COLD FRONT MOVING FROM THE LOWER GREAT
LAKES TO NEW ENGLAND...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

MODEL AGREEMENT IS GOOD WITH RESPECT TO THESE FEATURES. THE NAM
AND GFS ARE VERY CLOSE TO MODEL CONSENSUS AT THE SURFACE AND
UPPER-LEVELS.


...SHORTWAVE MOVING FROM THE CENTRAL ROCKIES TODAY INTO THE PLAINS
ON FRIDAY...

PRELIMINARY PREFERENCE: 12Z ECMWF
CONFIDENCE: AVERAGE

MODEL AGREEMENT IS GOOD THROUGH EARLY FRIDAY. AFTER THAT TIME THE
NAM BECOMES MORE AMPLIFIED AND SLOWER WITH THE WAVE RELATIVE TO
CONSENSUS...WHILE THE GFS IS LESS AMPLIFIED AND FASTER THAN
CONSENSUS. THE 12Z ECMWF AND CMC APPEAR TO BE IN BETWEEN THE NAM
AND GFS...AND CLOSE TO A CONSENSUS. THESE SOLUTIONS ARE ALSO
SUPPORTED BY THE 12Z ECMWF ENSEMBLE MEAN AND THE 18Z GEFS MEAN.


...SURFACE LOW PRESSURE SYSTEM CROSSING THE NORTHERN PLAINS AND
MIDWEST TODAY...

PRELIMINARY PREFERENCE: 12Z ECMWF
CONFIDENCE: AVERAGE

A SURFACE LOW IS FORECAST TO DEVELOP OVER NORTH DAKOTA TODAY IN
RESPONSE TO A VIGOROUS SHORTWAVE MOVING SOUTHEASTWARD THROUGH
CENTRAL CANADA. THE GFS APPEARS TO BE ON THE FAST SIDE OF THE
SPREAD WITH THE UPPER-LEVEL WAVE...AND AS A RESULT IS ALSO FASTER
THAN CONSENSUS WITH THE SURFACE LOW AS IT MOVES INTO ONTARIO EARLY
FRIDAY. THE SAME HOLDS TRUE FOR THE COLD FRONT MOVING INTO THE
PLAINS BEHIND THE SYSTEM. THE NAM SOLUTION IS CLOSER TO
CONSENSUS...ALBEIT JUST SLIGHTLY MORE AMPLIFIED WITH THE
UPPER-LEVEL WAVE EARLY SATURDAY...WHICH CAUSES ITS SURFACE LOW TO
LAG A BIT BEHIND THE 12Z ECMWF/GEM GLOBAL.


...UPPER-LEVEL LOW OVER BRITISH COLUMBIA...

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

THE NAM AND GFS ARE SIMILAR IN THEIR DEPICTION OF THIS
FEATURE...AND IN RELATIVELY GOOD AGREEMENT WITH MODEL CONSENSUS AS
THE LOW DRIFTS SOUTHEASTWARD THROUGH EARLY FRIDAY. AFTER THAT TIME
THE LOW WILL BECOME ABSORBED IN STRONGER UPPER-LEVEL FLOW AND
BEGIN TO MOVE EASTWARD. THE NAM AND GFS SHOW THIS PROCESS
OCCURRING IN A SIMILAR WAY TO THE 12Z ECMWF AND GEM GLOBAL.



...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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