Prognostic Meteorological Discussion
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000
FXUS10 KWNH 270505
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
104 AM EDT MON APR 27 2015

VALID APR 27/0000 UTC THRU APR 30/1200 UTC

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

12Z NAM/GFS EVALUATION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


DEEP TROUGH/CLOSED LOW CURRENTLY OVER THE SOUTHWEST U.S.
LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE THROUGH 12Z WED...GFS/12Z
ECMWF COMPROMISE THEREAFTER
CONFIDENCE: AVERAGE

THROUGH EARLY WED...THE MODELS ARE SHOWING BETTER AGREEMENT WITH
THE 00Z NAM TRENDING TOWARD THE SLOWER CONSENSUS.  THE NAM/GFS/12Z
ECMWF/12Z UKMET ARE FAIRLY WELL CLUSTERED THROUGH 12Z WED.
THEREAFTER...THE NAM REMAINS ON THE PROGRESSIVE SIDE OF THE
GUIDANCE WITH THE REMNANT SHORTWAVE MOVING ACROSS THE
SOUTHEAST/SOUTHERN MID-ATLANTIC AND THE SURFACE LOW TRACKING UP
THE SOUTHEAST COAST.


UPPER TROUGH DIGGING INTO THE GREAT LAKES LATE WED-THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z EC ENSMEAN/18Z GEFS MEAN
CONFIDENCE: BELOW AVERAGE

THERE IS BELOW AVERAGE CONFIDENCE ACROSS THE GREAT LAKES/OH VALLEY
LATE WED-THU AS A RESULT OF POOR RUN-TO-RUN CONTINUITY AND ABOVE
AVERAGE MODEL SPREAD WITH RESPECT TO THE EVOLUTION OF A SHORTWAVE
TROUGH FORECAST TO DIG INTO THE GREAT LAKES LATE WED-THU.  BY LATE
WED...THE NAM BEGAN TO TREND TOWARD A MORE AMPLIFIED SOLUTION OVER
THE GREAT LAKES...HOWEVER IT IS THE 00Z GFS/UKMET THAT ARE
SIGNIFICANT DEPARTURES FROM THEIR 12Z RUNS...NOW SHOWING A DEEP
LOW CLOSING OFF OVER THE GREAT LAKES LATE WED...BEFORE SETTING
INTO THE OH VALLEY BY EARLY WED.  AT THE MOMENT THESE TWO MODELS
ARE AT THE DEEP..SOUTHWEST SIDE OF THE GUIDANCE...WHILE THE
REMAINING MODELS ARE TO VARYING DEGREES MORE SHEERED AND FURTHER
TO THE NORTH.  WILL AWAIT THE 00Z ECMWF TO SEE IT FOLLOWS THE SAME
TREND AS THE GFS/UKMET...BUT FOR NOW AM HESITANT TO RECOMMEND
THEIR SOLUTIONS WITHOUT BROADER OPERATIONAL/ENSEMBLE
SUPPORT...INSTEAD SUGGESTING A MORE CONSERVATIVE APPROACH SIMILAR
TO THE LATEST ENSEMBLE MEANS.

UPPER TROUGHING OVER THE PACIFIC NORTHWEST TUE/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 00Z GFS IS MORE AMPLIFIED AND SLOWER WITH THE SHORTWAVE TROUGH
FORECAST TO MOVE ONSHORE LATE WED-THU...PUTTING IT INTO BETTER
AGREEMENT WITH NAM/12Z ECMWF.  THE 00Z UKMET HAS SLOWED AS
WELL...FURTHER BROADENING THE MODEL CONSENSUS.


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

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

PEREIRA

$$





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