Prognostic Meteorological Discussion
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000
FXUS10 KWNH 230701
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 AM EDT TUE SEP 23 2014

VALID SEP 23/0000 UTC THRU SEP 26/1200 UTC

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

...AN EVALUATION OF THE 23/00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE
23/00Z NAM/GFS WHICH IMPACTED THEIR FORECASTS.

...NORTHERN STREAM TROF EXITING NEW ENGLAND ON TUESDAY...

PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

A NEUTRAL TO NEGATIVELY-TILTED TROF IS FORECAST TO CONTINUE
LIFTING NORTH AND EAST TODAY WITH ADDITIONAL SHORTWAVES TRACKING
THROUGH UPPER NEW ENGLAND. ONLY SMALL DIFFERENCES ARE NOTED AMONG
THE AVAILABLE MODELS SO A GENERAL MODEL COMPROMISE WOULD BE FINE
HERE.

...UPPER LOW CUTTING OFF OVER THE CAROLINAS...
...INVERTED TROF ALONG THE EASTERN SEABOARD...

PREFERENCE: 23/00Z NAM/ECMWF INTO WED MORNING AND THEN  22/12Z
ECMWF ENS MEAN
FORECAST CONFIDENCE: LOW

WATER VAPOR IMAGERY FROM LATE MONDAY AFTERNOON INTO MONDAY EVENING
SHOWED A POTENT SHORTWAVE DIVING INTO THE DEEP SOUTH WITH A WELL
DEFINED TONGUE OF DRY AIR SPILLING IN BEHIND IT...WITH INCREASING
AGREEMENT IN THE MODELS THAT THE SYSTEM WILL NEARLY STALL AS IT
BECOMES CUT OFF FROM THE NORTHERN STREAM. THE GENERAL CLUSTERING
IN THE GUIDANCE IS REASONABLE FROM TODAY INTO WEDNESDAY MORNING
BEFORE THE FORECAST BECOMES MORE NEBULOUS.

AT THAT POINT...THE ECMWF ENS MEAN TENDS TO SPLIT THE DIFFERENCE
BETWEEN A WEAKER SOLN OFFERED FROM THE NAM/UKMET AND THE
ECMWF/CMC/GFS SOLNS.  WILL CONTINUE TO GIVE THE NOD TO THE 22/12Z
ECMWF ENS MEAN GIVEN ITS MARGINALLY BETTER CONSISTENCY THAN THE
OPERATIONAL RUNS PLUS THE FACT THAT CHANGES OVER THE PAST COUPLE
OF DAYS IN THE OPERATIONAL RUNS HAVE BEEN MORE TOWARDS THE EC ENS
MEAN IDEA.


...SLOW-MOVING UPPER TROF MOVING FROM THE CENTRAL GREAT BASIN TO
UPPER MIDWEST...

PREFERENCE: BLEND OF THE 00Z NCEP MODELS AND THE ECMWF
FORECAST CONFIDENCE: AVERAGE

OVERALL THE MODELS PAINT A FAIRLY UNIFORM PICTURE OF THE TROF
MOVING FROM THE GREAT BASIN TO THE UPPER MIDWEST INTO WEDNESDAY.
BY WEDNESDAY EVENING...THOUGH...THE 00Z GFS GETS AHEAD OF THIS
CONSOLIDATED SOLUTION AND CONTINUES PUSHING THIS ENERGY EASTWARD
ALONG THE SOUTHERN FRINGE OF THE WESTERLIES. THE ENSEMBLES FROM
THE DAYTIME RUNS SUPPORTED STALLING THE SYSTEM AND ALLOWING
SHORTWAVE ENERGY TO SLOWLY MIGRATE SOUTHWARD.

...WEAK AXIS OF VORTICITY LINGERING OVER THE SOUTHERN HIGH
PLAINS...

PREFERENCE: GENERAL BLEND THE 00Z GFS/ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

MODELS CONTINUE TO ADVERTISE A WEAKNESS IN THE MID-LEVEL FLOW
ACROSS THE SOUTHERN/CENTRAL PLAINS BY WEDNESDAY/THURSDAY. SEE NO
REASON TO STRAY FROM PREVIOUS RATIONALE FOR FAVORING A SOLUTION
SIMILAR TO THE SYSTEM ACROSS THE NORTHERN TIER GIVEN BOTH BECOME
EMBEDDED IN SOME FORM OF GENERAL WEAKNESS ACROSS THE CENTER OF THE
COUNTRY BY THURSDAY. THE NAM SOLN STOOD ALONE AND WOULD NOT
RECOMMEND IT ON DAY 3.

...FULL-LATITUDE TROF ALONG THE IMMEDIATE WEST COAST BY THURSDAY...

PREFERENCE: BLEND OF THE 22/12Z GEFS AND 22/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

THE PATTERN BECOMES QUITE AMPLIFIED ACROSS THE EASTERN PACIFIC AND
WESTERN U.S. WITH A RIDGE ANCHORING THE DESERT SOUTHWEST UP INTO
THE GREAT BASIN/ROCKIES. THE ENSEMBLE MEANS HAD FAIRLY GOOD
AGREEMENT AMONGST THEMSELVES AND CONTINUED TO HAVE THE SUPPORT OF
THE 22/12Z GEFS.

...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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