Prognostic Meteorological Discussion
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FXUS10 KWNH 081617
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1116 AM EST MON FEB 08 2016

VALID FEB 08/1200 UTC THRU FEB 12/0000 UTC

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

12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES

LOW PRESSURE FORMING OFF THE MID-ATLANTIC COAST TONIGHT/TUESDAY...

PREFERENCE: 3-WAY BLEND 12Z NAM/12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE

SMALL-SCALE DIFFERENCES EMBEDDED WITHIN THE UPPER TROUGH COMBINED
WITH MODESTLY STEEP MID LEVEL LAPSE RATES AND CLOSE PROXIMITY TO
THE LINGERING MOISTURE GRADIENT OFF THE COAST ARE CONTRIBUTING TO
CONTINUED MODEL SPREAD AND THEREFORE UNCERTAINTY WITH THE LOW
TRACK...ITS DEPTH...AND EVEN TIMING. THE NAM HAS THE ADVANTAGE OF
RECENT INITIALIZATION AND HIGH RESOLUTION BUT LIES NEAR THE STRONG
EDGE OF THE GUIDANCE AND IS CLOSER TO THE COAST BY LATE TUESDAY
COMPARED WITH MOST OTHER SOLUTIONS AND IS AGAINST RECENT TRENDS
FOR A LOW MORE OFFSHORE. THE GFS HAS A LOW TRACK AND DEPTH NEAR
THE CONSENSUS AND THEREFORE OFFERS ADVANTAGES BUT IS ALSO NEAR THE
COLD EDGE OF THE GUIDANCE ALOFT CONTRIBUTING TO ASCENT AND
MOISTURE SHIELDS THAT LIES NEAR THE HIGH END OF THE GUIDANCE. THE
06Z PARALLEL GFS IS MORE SUBDUED WITH THE COLDNESS ALOFT AND MAY
AFFORD AN EVEN MORE RELIABLE SOLUTION. THE 00Z ECMWF IS NEAR THE
SOUTHERN EDGE OF THE GUIDANCE BUT HAS SUPPORT FROM THE ITS OWN
ENSEMBLE MEAN/SREF MEAN AND THE 00Z UKMET. THUS...WHILE ONLY
MODESTLY SUPPORTED...WOULD PREFER TO SEE MORE RECENT GUIDANCE
SUPPORT IT TO RELY UPON IT ENTIRELY. THUS...THE MOST PREFERRED
APPROACH IS TO BLEND THE 12Z NAM/12Z GFS/00Z ECMWF AT THIS TIME.

LONGWAVE TROUGH EXTENDING SOUTHWARD FROM THE GREAT LAKES TUE-WED...
SURFACE TROUGH OVER NEW ENGLAND...

PREFERENCE: NAM
CONFIDENCE: AVERAGE

THE NAM REPRESENTS THE MODEL CONSENSUS THROUGH THIS PERIOD...WITH
THE 00Z ECMWF NEAR THE SOUTHERN EDGE OF THE GUIDANCE AND THE GFS
NEAR THE COLD EDGE OF THE GUIDANCE THAT APPEARS TO TRANSFER TO A
STRONGER SURFACE TROUGH OVER NEW ENGLAND ON THURSDAY THAN
PREFERRED AT THIS TIME.

LOW PRESSURE MOVING FROM MONTANA TO TEXAS WED-THU...

PREFERENCE: NAM OR GFS
CONFIDENCE: AVERAGE

ALTHOUGH THE NAM IS A LITTLE STRONGER WITH THE LEE LOW FORMING
DOWNWIND OF THE CANADIAN ROCKIES COMPARED TO THE GFS...THEY ARE
CONCEPTUALLY SIMILAR AND STRONGER THAN THE 00Z ECMWF TRACKING
SOUTHEASTWARD WITH A ZONE OF FRONTOGENESIS. GIVEN THEIR AGREEMENT
AND MORE RECENT INITIALIZATION...THEY ARE MORE RECOMMENDED
COMPARED TO THE ECMWF.

SHORTWAVE TROUGH INFLUENCING THE PACIFIC NORTHWEST WED-THU...

PREFERENCE: NAM OR ECMWF
CONFIDENCE: ABOVE AVERAGE

THE GFS LIES NEAR THE STRONG AND FAST EDGES OF THE GUIDANCE AND
MAY BE SHOWING ITS OCCASIONAL FAST BIAS. GIVEN THE STRONG RIDGE
ACROSS THE WEST AT THIS TIME...THE PREFERENCE IS FOR PERSISTENCE
AND THEREFORE THE WEAKER NAM/ECMWF.

...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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