Prognostic Meteorological Discussion
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FXUS10 KWNH 171837
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 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 STORM ODILE...

PREFERENCE: THE LATEST NHC TRACK FORECAST

T.S. ODILE CONTINUES TO LIFT NORTHEAST ACROSS THE NORTHERN GULF OF
CALIFORNIA AND IS EXPECTED TO MOVE INLAND OVER THE NEXT 6 TO 12
HOURS OVER NWRN MAINLAND MEXICO. MEANWHILE...THE SYSTEM SHOULD
WEAKEN RAPIDLY AND 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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