Prognostic Meteorological Discussion
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FXUS10 KWNH 171903
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 PM EDT WED SEP 17 2014

VALID SEP 17/1200 UTC THRU SEP 21/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE
ECMWF


...TROPICAL DEPRESSION ODILE...

PREFERENCE: THE LATEST NHC TRACK FORECAST

T.D. ODILE HAS MADE LANDFALL AS OF THE 18Z NHC INTERMEDIATE
ADVISORY OVER NORTHWESTERN MEXICO AND IS EXPECTED TO MOVE FARTHER
INLAND WHILE RAPIDLY WEAKENING OVER THE NEXT 24 HOURS. THE SYSTEM
SHOULD BEGIN TO SHEAR APART WITH A MID LEVEL CENTER RACING AND
SHEARING EAST-NORTHEAST ACROSS THE SOUTHERN ROCKIES AND OUT INTO
THE SOUTHERN HIGH PLAINS OVER THE NEXT COUPLE OF DAYS. THE LATEST
NHC TRACK FORECAST IS CLOSEST TO A BLEND OF THE 12Z UKMET AND 12Z
ECMWF. THE ENERGY ALOFT SHEARING DOWNSTREAM SHOULD TEND TO BE MORE
PROGRESSIVE. THE UKMET AND ECMWF THOUGH HAVE SHIFTED THEIR
RESPECTIVE TRACKS OF THE VORT ENERGY FARTHER SOUTH...SUGGESTING
THAT THE NAM AND GFS ARE TOO FAR NORTH. THERE IS EVIDENCE THAT THE
GFS IS SUFFERING FROM CONVECTIVE FEEDBACK PROBS AND AS RESULT
PLACING ITS VORT TOO FAR NORTH OVER THE SOUTHERN HIGH PLAINS. THE
NAM ASSUMES A MORE NORTHEAST TRACK...BUT EVEN THE LATEST SAT
TRENDS SUGGEST A MOTION MORE TO THE EAST-NORTHEAST. SO...BASED ON
THIS...A SOLN MORE CLOSELY TIED TO A 12Z UKMET/12Z ECMWF BLEND
APPEARS REASONABLE WITH THE ENERGY SHEARING DOWNSTREAM.


...DEEP UPPER TROUGH AFFECTING THE WESTERN STATES THROUGH SAT...

PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE LARGER SCALE RIDGE POSITIONED OVER THE WESTERN U.S. WILL SHIFT
EASTWARD AHEAD OF A BROAD UPPER TROUGH OFFSHORE THE WEST COAST
THAT WILL BE DIGGING INTO THE SOUTHWEST U.S. BY FRI. IN GENERAL
ALL OF THE MODELS SHOW VERY GOOD MASS FIELD AGREEMENT WITH THE
EVOLUTION OF THIS SYS THROUGH SAT. THE OVERALL BEST MODEL
CLUSTERING WOULD SUPPORT A BLEND OF THE 12Z GFS AND 12Z
ECMWF...AND THAT WILL BE THE PREFERENCE.


...UPPER TROUGH OVER THE NORTHEAST...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

AN UPPER TROUGH WILL BE SWINGING THROUGH THE NORTHEAST OVER THE
NEXT 36 HOURS...AND THE LATEST GLOBAL MODELS SHOW EXCELLENT MASS
FIELD AGREEMENT THROUGH THAT TIME PERIOD AS THE ENERGY THEN LIFTS
ACROSS EASTERN CANADA. A GENERAL MODEL COMPROMISE WILL BE
PREFERRED.


...UPPER TROUGH DIGGING INTO THE NORTHERN PLAINS ON FRI...

PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF
CONFIDENCE: AVERAGE

ALL OF THE MODELS INDICATE A TROUGH DIGGING INTO THE NORTHERN
PLAINS ON FRI ALONG WITH A COLD FRONT. THE 12Z UKMET AND 12Z GEM
ARE MUCH MORE PROGRESSIVE AND SHEARED WITH THEIR SHORTWAVE ENERGY
DIGGING ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST. THE 12Z
GFS/12Z ECMWF AND ESP THE 12Z NAM ARE SLOWER. THE 12Z NAM APPEARS
AS IF IT MAY BE A LITTLE TOO AMPLIFIED. WILL PREFER A BLEND OF THE
12Z GFS AND 12Z ECMWF BASED ON STRONGER MODEL CLUSTERING.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

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