Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300408
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1208 AM EDT SAT MAY 30 2015

VALID MAY 30/0000 UTC THRU JUN 02/1200 UTC

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

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

...SHORTWAVE TROUGH THE CENTRAL PLAINS...
...MCV AND ATTENDANT SURFACE LOW OVER THE MIDDLE MS VALLEY...
...NORTHERN STREAM ENERGY CROSSING THE GREAT LAKES MON AND TUES...

PREFERENCE: 00Z GFS
CONFIDENCE: AVERAGE

THE MODELS SHOW REASONABLY GOOD AGREEMENT WITH THE NORTHEASTWARD
ADVANCE OF THE MCV THE THAT IS NOW OVER THE MID MS VALLEY REGION.
THIS ENERGY WILL SHEAR AND DAMPEN OUT OVER THE OH VALLEY ON SAT AS
NORTHERN STREAM ENERGY EJECTS EAST FROM THE CENTRAL PLAINS AND
GRADUALLY ADVANCES THROUGH THE OH VALLEY SAT AND SUN BEFORE
WEAKENING. THE 12Z UKMET APPEARS TO BE TOO WEAK WITH THE MCV WITH
THE REMAINING MODELS WELL CLUSTERED WITH ITS STRENGTH AS IT
WEAKENS WITH TIME. THE INFUSION OF NORTHERN STREAM ENERGY SHOULD
HELP TO SUSTAIN AN AREA OF LOW PRESSURE ORIGINALLY ATTACHED TO THE
MCV...AND THE MODELS ARE IN GOOD AGREEMENT IN TRACKING THIS WAVE
INTO UPPER OH VALLEY AND MID-ATLANTIC REGION BY MON. THE 12Z ECMWF
APPEARS A LITTLE SLOW...WITH THE 12Z GEM AND ESPECIALLY THE 12Z
UKMET TOO FAST. THE 00Z NAM AND 00Z GFS ARE GENERALLY WELL
CLUSTERED IN BETWEEN WITH THE DETAILS OF THIS THROUGH 48 HOURS.
AFTER 48 HOURS...THE ARRIVAL OF ADDITIONAL NORTHERN STREAM
TROUGHING THROUGH THE GREAT LAKES REGION IS EXPECTED TO CAPTURE
THIS AREA OF LOW PRESSURE. THE NAM AND GFS BOTH ARE FAIRLY
AGGRESSIVE IN LIFTING THE SURFACE LOW ON TUES UP NEAR THE NEW
ENGLAND COAST. THE UKMET IS ALREADY OFFSHORE BY TUES...WITH THE
ECMWF SLOWER. BASED ON THE LATEST TRENDS AND MODEL
CLUSTERING...THE GFS REMAINS A REASONABLE SOLUTION AND GIVEN
BETTER OVERALL ENSEMBLE SUPPORT...THE GFS WILL REMAIN THE
PREFERENCE.


...SHORTWAVE TROUGH OVER THE SOUTHERN ROCKIES...

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

THE 00Z NAM STILL FAVORS PORTIONS OF THE TROUGH TO SLOW DOWN AND
POSSIBLY BREAK OFF FROM THE WESTERLIES ACROSS THE MIDDLE/LOWER MS
VALLEY THROUGH THE PERIOD. THE 12Z ECMWF AND ESPECIALLY THE 12Z
UKMET ARE WEAKER AND MORE PROGRESSIVE. THE 12Z GEM TENDS TO BE A
BIT DEEPER THAN THE ECMWF AND UKMET...BUT IS FASTER THAN THE NAM
AND GFS. THE 00Z GFS WHICH HAD BEEN SLOWER/DEEPER LIKE THE NAM HAS
NOW JOINED THE NON-NCEP CAMP IN TIMING AND STRENGTH OVERALL.
THEREFORE...A NON-NAM CONSENSUS WILL BE PREFERRED...LED BY A BLEND
OF THE 00Z GFS AND 12Z ECMWF.


...SHORTWAVE TROUGH REACHING THE NORTHWEST BY MON...

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

AN UPPER LOW AND ASSOCIATED TROUGH AXIS POSITIONED NEAR 35N 147W
WILL MOVE EAST PROGRESSIVELY EAST OVER THE NEXT COUPLE OF DAYS AND
ADVANCE INTO THE NORTHWEST U.S. BY MON OUT AHEAD OF A STRONGER
CORE OF WESTERLIES AND ENERGY SOUTH OF THE ALEUTIANS. THERE IS
EXCELLENT AGREEMENT ALOFT WITH THE EVOLUTION OF THE HEIGHT
FALLS...HOWEVER THERE IS A LITTLE MORE SPREAD WITH THE ATTENDANT
SURFACE LOW. THE 12Z UKMET AND 12Z GEM BOTH TENDED TO HANG ONTO A
SOMEWHAT STRONGER SURFACE WAVE APPROACHING THE PACIFIC NORTHWEST
BY EARLY MON...WITH THE 00Z NAM/00Z GFS AND 12Z ECMWF ALL A LITTLE
WEAKER. THE ENSEMBLE MEANS FAVOR THE SLIGHTLY WEAKER
CONSENSUS...AND SO A BLEND OF THE NAM/GFS AND ECMWF 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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