Prognostic Meteorological Discussion
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FXUS10 KWNH 270721
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
320 AM EDT MON JUL 27 2015

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

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

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

...SHORTWAVE IMPULSE CROSSING THE NORTHERN PLAINS/UPPER MIDWEST...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

A SHORTWAVE IMPULSE CURRENTLY EJECTING EAST ACROSS THE UPPER
MIDWEST WILL ADVANCE DOWNSTREAM AND BEGIN TO SHEAR OUT ACROSS
PORTIONS OF THE GREAT LAKES REGION THROUGH MON. THE 00Z NAM
REMAINED A STRONG OUTLIER SOLN AND WAS DISCOUNTED.  OTHER GLOBAL
MODELS WERE IN GOOD TO EXCELLENT AGREEMENT WITH THE IDEA OF A MORE
SHEARED OUT/WEAKER SYSTEM.  AMONG THE GLOBAL MODELS ON A MORE
SHEARED/WEAKER SYSTEM BY COMPARISON.


...UPPER LOW/TROUGH DIGGING THROUGH THE NORTHWEST...
...ENERGY TRAVERSING THE NORTHERN PLAINS/UPPER MIDWEST...
...CYCLOGENESIS OVER THE NORTHERN HIGH PLAINS...

PREFERENCE: ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AN UPPER LOW AND ASSOCIATED TROUGH WILL DIG SOUTHEAST FROM BRITISH
COLUMBIA/WASHINGTON AND MOVE ACROSS THE NORTHWEST U.S. THROUGH THE
DAY TODAY BEFORE EJECTING EAST OUT ACROSS THE NORTHERN PLAINS AND
UPPER MIDWEST TUES AND WED. MEANWHILE...LEE-SIDE CYCLOGENESIS OVER
THE NORTHERN HIGH PLAINS WILL OCCUR BY EARLY MON...WITH THE
GUIDANCE AGREEING ON THE DEVELOPMENT OF LOW PRESSURE OVER
SOUTHEAST MT.

THE NAM LOOKED TO BE A STRONG OUTLIER AND WAS GIVEN MINIMAL
CONSIDERATION.  HAVE OPTED AGAINST THE GFS STARTING TUESDAY
AFTERNOON SINCE GRID SCALE FEEDBACK APPEARED TO ADVERSELY IMPACT
THE FORECAST OVER A FAIRLY LARGE PART OF THE UPPER MIDWEST TUESDAY
AFTERNOON AND TUESDAY NIGHT.  THE ECMWF HAD GOOD RUN TO RUN
CONSISTENCY AND WAS FAVORED...ALTHOUGH THE CANADIAN AND UKMET
SOLNS WERE IN THE SAME BALLPARK.

...MID LEVEL TROUGH IMPACTING THE SOUTHEAST/FL PENINSULA...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS MAINTAIN AN ELONGATED MID LEVEL TROUGH AXIS FROM THE
EASTERN GULF OF MEXICO TO THE SOUTHWEST ATLANTIC BASIN THROUGH THE
PERIOD. THE GLOBAL MODELS ARE CLUSTERED WELL ENOUGH OTHERWISE THAT
A NON-NAM CONSENSUS CAN BE PREFERRED.


...UPPER TROUGH REDEVELOPING OFF THE EAST COAST MON AND TUES...

PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/CMC
CONFIDENCE: AVERAGE

THE MODELS STRONGLY FAVOR THE IDEA OF A TROUGH RELOADING ALOFT OFF
THE EAST COAST BY TUES AS ENERGY OVER SOUTHEAST CANADA INCLUDING A
CLOSED LOW DROPS SOUTHEAST AND COUPLES WITH LEFTOVER ENERGY
SHEARING THROUGH THE GREAT LAKES ASSOCIATED WITH THE CURRENT UPPER
MIDWEST SHORTWAVE TROUGH. THE GUIDANCE ALSO FAVORS DEVELOPING LOW
PRESSURE WELL OFF THE EAST COAST. THE 00Z NAM REMAINS AS A
STRONGER OUTLIER WITH THE HEIGHT FALLS AND ALSO DEVELOPING SURFACE
LOW PRESSURE WHILE THE 00Z ECMWF HAD GOOD RUN TO RUN CONTINUITY.
THE LATEST UKMET TRENDED WEAKER/FASTER WITH THE WAVE AS IT DEEPENS
AND THEN MOVES OFF SHORE...WHILE THE CMC WAS STRONGER/SLOWER WITH
THE WAVE WHEN COMPARED WITH ITS PREVIOUS RUN.  THE 00Z
GFS/CMC/ECMWF SPLIT THE DIFFERENCE WITH RESPECT TO THE DEPTH OF
THE UPPER TROF.  THIS IDEA ALSO HAS SUPPORT FROM THE ENSEMBLE
MEAN.  AS A RESULT...A BLEND OF THESE SOLUTIONS REMAINS 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...

BANN

$$





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