Prognostic Meteorological Discussion
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FXUS10 KWNH 021717
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
117 PM EDT TUE JUN 02 2015

VALID JUN 02/1200 UTC THRU JUN 06/0000 UTC

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

WELL DEVELOPED NORTHERN STREAM UPPER LOW ROLLING ACROSS NEW ENGLAND
SURFACE LOW PASSING JUST OFF NOVA SCOTIA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

NO SIGNIFICANT MODEL DIFFERENCES WERE NOTED...ABOVE AVERAGE
CONFIDENCE EXITS GIVEN THE SHORT TERM NATURE OF THE FORECAST AND
VERY GOOD AGREEMENT AMONG THE LATEST GUIDANCE.


CLOSED LOW FORECAST TO WEAKEN EWD ACROSS THE SRN APPALACHIANS
  THROUGH THE END OF THE WORK WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 00Z ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z NAM/GFS HAVE BOTH TRENDED A BIT FASTER WITH THE EWD
PROGRESSION OF THE MID-LEVEL CLOSED LOW TRACKING EAST ACROSS THE
SRN APPALACHIANS BY THU EVENING. THE NAM IS THE FASTEST...FOLLOWED
BY THE GFS...WITH THE 00Z ECMWF/UKMET LAGGING SLIGHTLY BEHIND BY
THU EVENING. THE 00Z CMC IS SLOWEST WITH THE PROGRESSION BY FRI
EVENING. ALTHOUGH TRENDS IN MUCH OF THE GUIDANCE HAVE BEEN
FASTER...THE ENSEMBLE MEANS...INCLUDING THE 09Z SREF...STILL
SUPPORT A PROGRESSION SIMILAR TO THE 00Z ECMWF/UKMET. GIVEN THE
SLOW PROGRESSION OF THIS TROUGH TO DATE...AND THE PRESENCE OF
RIDGING ACROSS THE WRN ATLANTIC...PREFER TO NOT JUMP ON THE
FASTEST SOLUTIONS AT THIS TIME.


SHORTWAVE SHEARING OUT ALONG U.S./CANADIAN BOARDER
NORTHERN HIGH PLAINS CYCLOGENESIS
SOUTHERN STREAM SHORTWAVE EJECTING INTO CENTRAL PLAINS THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 00Z ECMWF
            12Z GFS SECONDARY PREFERENCE AFTER 12Z FRI
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A COMPLEX SITUATION FORECAST ACROSS THE PLAINS WITHIN SOUTHWEST
FLOW ALOFT AND WEAK IMPULSES EJECTING OUT FROM THE WESTERN CONUS.
CONVECTIVE DETAILS MUDDLE THE FORECAST AND FEATURES ARE DIFFICULT
TO TRACK GIVEN RELIANCE ON YET TO BE SEEN CONVECTIVELY DRIVEN
VORTICITY MAXIMA.

HOWEVER...THE NAM REMAINS A STRONGER OUTLIER WITH SHORTWAVE ENERGY
REACHING THE UPPER MIDWEST EARLY THU MORNING WITH THE GFS FLATTEST
OF THE DETERMINISTIC GUIDANCE. THE 00Z ECMWF/UKMET SEEM TO BE IN
AGREEMENT WITH EACH OTHER AND THE ENSEMBLE MEANS HERE...BUT THE
UKMET APPEARS TO DEVELOP CONVECTIVE FEEDBACK ACROSS THE CNTRL HIGH
PLAINS THU MORNING WHICH CONTAMINATES THE FORECAST INTO FRI. THE
WEAKER SOLUTION ALOFT IN THE 12Z GFS MAY BE CAUSING THE FRONTAL
BOUNDARY ACROSS THE PLAINS TO BE TOO FAR NORTH. OFTEN TIMES IT
SEEMS THE MODELS CAN BE TOO FAR NORTH WITH FRONTS/CONVECTION IN
THESE TYPES OF SETUPS ACROSS THE PLAINS. THE 00Z ECMWF APPEARS TO
BE THE MOST RELIABLE MODEL FROM TODAY THROUGH FRI EVENING...WITH
THE 12Z GFS A SECOND CHOICE FOR FRI ACROSS THE PLAINS AS EARLIER
DIFFERENCES ARE NO LONGER AN ISSUE BACK ACROSS THE PLAINS.


UPPER TROUGH RELOADING OVER THE WEST BY WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z UKMET BLEND
CONFIDENCE: ABOVE AVERAGE

ONLY MINOR PLACEMENT/TIMING DIFFERENCES EXIST WITH A CLOSED LOW
FORECAST TO FORM OVER CALIFORNIA BY MID-DAY THURSDAY. THE 00Z
UKMET DOES STAND OUT ENOUGH BY FRI EVENING HOWEVER...WITH A
SOMEWHAT MORE OPEN AND NEWD PROGRESSION. GIVEN GOOD AGREEMENT
OUTSIDE OF THE 00Z UKMET...THE PREFERENCE IS FOR A NON 00Z UKMET
BLEND OF MODELS.


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

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

OTTO

$$





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