Prognostic Meteorological Discussion
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000
FXUS10 KWNH 270650
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 AM EDT WED JUL 27 2016

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 NAM/GFS/UKMET/CMC AND ECMWF


...MULTIPLE SHORTWAVES MOVING EAST OVER THE SOUTHWEST
RIDGE...DROPPING SOUTHEAST INTO A DEVELOPING EAST COAST TROUGH...
...SHORTWAVE ENERGY MOVING NORTH THROUGH THE LOWER MS
VALLEY...BECOMING ABSORBED INTO THE EAST COAST TROUGH...

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

A COMPLEX PATTERN OVER THE CONUS FOR THE SHORT TERM PERIOD...WITH
THE FORECAST AGAIN EXPECTED TO BE INFLUENCED BY SMALL SCALE
CONVECTIVE FEATURES/VORTS...WHICH WILL BE DIFFICULT TO TRACK. ON
THE LARGE SCALE THERE IS PRETTY GOOD AGREEMENT AMONGST THE
MODELS...WITH A SOUTHWESTERN U.S. UPPER RIDGE...AND A DEVELOPING
BROAD TROUGH OVER THE EASTERN HALF OF THE NATION. HELPING TO
DEVELOP THIS TROUGHING WILL BE MULTIPLE SHORTWAVES RIDING UP AND
OVER THE RIDGE AND DIGGING SOUTHEAST ACROSS THE MS VALLEY AND INTO
THE EAST. THERE IS REASONABLY GOOD AGREEMENT AS WELL THAT THE MID
LEVEL TROUGH/CLOSED LOW OVER THE LOWER MS VALLEY WILL BE PULLED
NORTH AND GRADUALLY ABSORBED INTO THE TROUGH.

THE DISAGREEMENT COMES FROM THE TIMING/STRENGTH OF TWO SHORTWAVES
MOVING OVER THE RIDGE ACROSS THE PLAINS AND ALSO WITH THE LOWER MS
VALLEY ENERGY...AND HOW THESE SYSTEMS INTERACT WITH EACH OTHER.
DIFFERENCES WITH THE FIRST SHORTWAVE DROPPING SOUTHEAST ACROSS THE
NORTHERN PLAINS AND MIDWEST WED AND THURS ARE FAIRLY
MINOR...ALTHOUGH THE 00Z NAM DOES HAVE SLIGHTLY MORE AMPLIFICATION
THAN THE GLOBAL MODELS. THIS ENERGY IS EXPECTED TO ABSORB THE MID
LEVEL LOW/TROUGH OVER THE LOWER MS VALLEY AND PULL THE REMNANT
ENERGY NORTHEAST INTO THE OH VALLEY AND MID-ATLANTIC REGION
THROUGH FRI AND THIS IS WHEN MORE NOTABLE MODEL DIFFERENCES ARE
SEEN. THE 00Z NAM AND 00Z GFS BECOME A LITTLE FASTER THAN THE 00Z
UKMET/00Z CMC AND 00Z ECMWF BY FRI...WITH THE 00Z CMC BECOMING THE
SLOWEST. A WAVE OF LOW PRESSURE WILL DEVELOP ALONG A FRONT AND
WILL TRAVERSE THE OH VALLEY/MID-ATLANTIC REGION THURS AND
FRI...AND THE UKMET AND CMC BOTH TEND TO HAVE SLOWER SOLUTIONS
VERSUS THE NAM/GFS AND ECMWF.

UPSTREAM A SECOND SHORTWAVE WILL BE DIGGING DOWN FROM THE PLAINS
AND ACROSS THE MIDWEST FRI AND SAT. THE CMC AND ESPECIALLY THE NAM
APPEAR TO BE TOO DEEP AND A LITTLE TOO SLOW. IN FACT...THE NAM
DEVELOPS A WELL-DEFINED SURFACE WAVE OVER THE MIDWEST BY SAT WHICH
IS NOT WELL SUPPORTED BY THE OTHER MODELS. THE GFS/UKMET AND ECMWF
ARE ALL A LITTLE MORE PROGRESSIVE WITH THE ENERGY AND HAVE WEAKER
SURFACE REFLECTIONS. ALONG THE EAST COAST BY SAT...THE GFS AND
ECMWF TEND TO COME INTO BETTER AGREEMENT WITH THEIR SURFACE WAVE
DETAILS AND IS RATHER WELL SUPPORTED BY THE UKMET AND THE LATEST
GEFS MEAN AND ECENS MEAN. THE CMC AND NAM EVENTUALLY APPEAR TO BE
TOO STRONG WITH THEIR LOWS EXITING OFFSHORE...AND SO WILL
THEREFORE PREFER A BLEND OF THE GFS AND ECMWF.


...SHORTWAVE TROUGH AIMING FOR THE NORTHWEST BY SAT...

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

THE GUIDANCE HAS A SHORTWAVE TROUGH CROSSING THE GULF OF AK AND
DROPPING SOUTHEAST ACROSS BRITISH COLUMBIA BY FRI..WITH THE ENERGY
CLIPPING THE NORTHWEST U.S. ON SAT. THE 00Z CMC APPEARS TO BE A
BIT SLOWER AND DEEPER THAN THE MODEL CONSENSUS WITH THIS SYSTEM.
THE 00Z UKMET AND 00Z NAM ALSO APPEAR TO MAYBE BE A LITTLE TOO
SLOW. THE BEST OVERALL MODEL CLUSTERING AND ENSEMBLE SUPPORT
RESIDES WITH THE 00Z GFS AND 00Z ECMWF...AND THUS A BLEND OF THESE
SOLUTIONS WILL BE PREFERRED.

ORRISON

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

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

$$




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