Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8
000
FXUS10 KWNH 210458
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1257 AM EDT SUN SEP 21 2014

VALID SEP 21/0000 UTC THRU SEP 24/1200 UTC

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...EASTERN U.S...INCLUDING A COASTAL LOW...

PREFERENCE DAY 2:  BLEND OF 21/00Z NAM/GFS
PREFERENCE DAY 3:  21/00Z NAM/GFS/GEFS MEAN
CONFIDENCE: AVERAGE

MODELS ARE NOW SIMILAR IN HANDLING THE TRACK AND TIMING OF COASTAL
LOW PRESSURE AS IT PARALLELS THE ATLANTIC COAST BEFORE BEING
ABSORBED AHEAD OF A SYNOPTIC LOW/FRONT NEAR NEW ENGLAND. THE
21/00Z NAM BACKED AWAY FROM ITS DEEPER SOLN IN HOW IT HANDLES THE
TROF OVER THE EASTERN STATES GETTING IT IN BETTER OVERALL
AGREEMENT WITH THE GFS AND THE PREVIOUS GEFS MEAN.  THE GFS
CONTINUITY WAS PRETTY GOOD IN HANDLING THIS FEATURE WHEN COMPARED
WITH THE 20/12Z GFS.

BY DAY 3...THE 20/12Z ECMWF WANTS TO DROP SHORTWAVE ENERGY INTO
THE SOUTHEAST...MUCH LIKE THE NAM/GFS...BUT THEN SLOW IT DOWN AND
DEEPEN IT IN OPPOSITION TO OTHER MODELS.  THE ECMWF ENS MEAN WOULD
TEND TO ARGUE AGAINST THAT SOLN.  WHILE THERE MAY BE SOME LOWER
HEIGHTS LEFT BEHIND OVER THE SOUTHEAST DURING THE LATTER HALF OF
DAY 3 AS SUGGESTED BY THE PREVIOUS CANADIAN...THINK THE OPNL ECMWF
WOULD BE TOO DEEP GIVEN THE OVERALL SYNOPTIC PATTERN. THE ECMWF
ALSO SEEMS TO BE THE MOST BULLISH IN BUILDING A SHORT LIVED MID
LEVEL HIGH OVER THE SOUTHERN GREAT LAKES AT AROUND 24/06Z.

...SHEAR AXIS TRAPPED IN THE UPPER RIDGE BUILDING OVER THE
SOUTHERN PLAINS...

PREFERENCE: A NON NAM BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: AVERAGE

OVERALL AGREEMENT IN THE MODEL MASS FIELDS WAS GOOD HERE WHILE THE
NAM BECOMES A BIT OF AN EASTWARD OUTLIER IN TERMS OF MOISTURE BY
DAY 3 OVER PARTS OF TX.

...SYSTEM TRACKING FROM CALIFORNIA TO THE NORTHERN PLAINS...

PREFERENCE: ANY OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

THE OPERATIONAL MODELS STILL SHOW STRONG AGREEMENT AT THE SURFACE
AND ALOFT.


...DEEP TROUGH LEANING INTO THE PACIFIC NORTHWEST...

PREFERENCE: ANY OF THE 00Z RUNS OR 12Z ECMWF/UKMET...LESS WEIGHT
ON THE 12Z CANADIAN
CONFIDENCE: ABOVE AVERAGE

A LEAD SHORTWAVE WILL BRING HEIGHT FALLS AND THE ONSET OF LIGHT
PRECIPITATION WEST OF THE WA/OR CASCADES ON MONDAY. THE WAVE WILL
PUSH A WEAK BOUNDARY INTO THE NORTHERN ROCKIES MON/TUE. A DEEPER
LONGWAVE TROUGH WILL APPROACH THE COAST BY LATE TUESDAY AND INTO
WEDNESDAY. MODEL AGREEMENT IN THE 00Z PRODUCTION CYCLE IS STILL
STRONG...ASIDE FROM THE 20/12Z CANADIAN WHICH HAS SHOWN MORE RUN
TO RUN VARIABILITY WITH RESPECT TO SHORTWAVE TIMING AND STRENGTH.

...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

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.