Prognostic Meteorological Discussion
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000 FXUS10 KWNH 011854 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 254 PM EDT MON SEP 01 2014 VALID SEP 01/1200 UTC THRU SEP 05/0000 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 ...TROUGH SLIDING FROM THE MIDWEST TO THE NORTHEAST THROUGH WED... PREFERENCE: NON-GEM CONSENSUS CONFIDENCE: AVERAGE THIS TROUGH CONSISTS OF A LEAD SHORTWAVE AND A SMALLER SHORTWAVE THAT QUICKLY FOLLOWS OVER THE NEXT COUPLE OF DAYS. THE COMBINATION OF THE TWO WILL DRIVE A COLD FRONT THROUGH THE NORTHERN AND NORTHEASTERN U.S...WHILE THE TAIL END STALLS IN THE MID MS VLY AND CNTRL PLAINS. IN GENERAL THERE IS GOOD MODEL MASS FIELD AGREEMENT WITH THE LARGER SCALE TROUGH AXIS. HOWEVER...THE 12Z GFS IS SEEN AS BEING A TAD SLOWER THAN THE 12Z NAM AND THE REMAINING NON-NCEP SOLNS INCLUDING THE 12Z UKMET/12Z GEM AND 12Z ECMWF. AT THE SFC THOUGH......THE 12Z ECMWF AND 12Z UKMET HAVE TRENDED TWD THE 12Z GFS AND 12Z NAM IDEA OF A RELATIVELY WEAKER/FLATTER WAVE THAT IMPACTS THE ST LAWRENCE RIVER VALLEY AND SRN QUEBEC. THE 12Z GEM IS NOW VIEWED AS A STRONG OUTLIER...AND EVEN THOUGH THE 00Z ECENS MEAN SUPPORTS A STRONGER SFC WAVE...THE TRENDS IN THE 12Z GUIDANCE COLLECTIVELY SUPPORT THE IDEA OF LEANING TWD A MORE PROGRESSIVE/WEAKER SOLN. THEREFORE...WILL FAVOR A NON-GEM CONSENSUS ATTM. ...PACIFIC TROUGH AFFECTING THE WEST AND SPILLING INTO THE NORTHERN PLAINS LATE WED... ...LINGERING TROUGH/WEAKNESS LEFT OVER THE NORTHWEST... PREFERENCE: BLEND OF 12Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS INDICATE A PROGRESSIVE BUT RATHER VIGOROUS TROUGH DIGGING INTO THE NORTHWEST ON TUES AND THEN MOVING EAST OUT INTO THE NRN PLAINS BY WED. MEANWHILE...ALL OF THE MODELS BY WED AND THURS SHOW A TAIL OF ENERGY OR WEAKNESS LEFT BEHIND THE MAIN SHORTWAVE TROUGH THAT WILL BE SITUATED OVER THE NORTHWEST AND DOWN INTO NRN CA WHERE IT WILL BE ATTEMPTING TO INTERACT WITH ENERGY OFFSHORE OF CA. THE 12Z UKMET AND 12Z GEM ARE FASTER WITH THE HEIGHT FALLS THAT EJECT OUT ACROSS THE NRN PLAINS VS THE RELATIVELY SLOWER 12Z GFS/12Z NAM AND 12Z ECMWF. THE SAME APPLIES TO THE SFC LOW EVOLUTION THROUGH THE PERIOD...ALTHOUGH THE 12Z NAM IS SEEN MOST TIME FRAMES AS BEING A TAD NORTH OF THE GLOBAL MODEL CONSENSUS. THE LATEST GEFS MEAN AND ECENS MEAN FAVOR A SOMEWHAT SLOWER SOLN AND SUPPORT THE DETERMINISTIC GFS AND ECMWF CAMP. OVER THE NORTHWEST ON WED AND THURS...THERE IS NOT AS MUCH SPREAD WITH THE GUIDANCE. BASED ON THE CURRENT DEGREE OF SPREAD AND CLUSTERING...FEEL LIKE A BLEND OF THE 12Z GFS AND 12Z ECMWF WILL SUFFICE FOR THE TIME BEING. ...BROAD AREA OF LOW PRESSURE ENTERING THE BAY OF CAMPECHE... PREFERENCE: LATEST NHC TROPICAL WEATHER OUTLOOK A BROAD AREA OF LOW PRESSURE IS ADVANCING INTO THE BAY OF CAMPECHE FROM THE YUCATAN PENINSULA TODAY. THE NATIONAL HURRICANE CENTER FORECASTS A 80 PERCENT CHANCE OF TROPICAL CYCLONE FORMATION WITHIN THE NEXT 48 HOURS. THE MODEL SPREAD REMAINS RATHER MINIMAL REGARDING THE TRACK...WITH THE GUIDANCE SUGGESTING THAT THE LOW CENTER MOVES INTO NERN MEXICO BY WED. HOWEVER...IT SHOULD BE NOTED THAT THE 12Z NAM AND 12Z UKMET SHOW CONSIDERABLY MORE VERTICAL DEVELOPMENT AND ORGANIZATION COMPARED TO THE RELATIVELY WEAKER 12Z GFS AND 12Z ECMWF. THE 12Z GEM TENDS TO SPLIT THE DIFF. PLS CONSULT THE LATEST NHC TROPICAL WEATHER OUTLOOK FOR MORE INFORMATION ON THIS SYS. ...EASTERLY WAVE APPROACHING FLORIDA... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: AVERAGE AN EASTERLY WAVE APPROACHING THE BAHAMAS WILL BE ADVANCING ACROSS SRN FL AND THE FL KEYS BY WED. THE 12Z NAM APPEARS TO BE TOO STRONG WITH THE WAVE AXIS. THE 12Z GFS ALONG WITH THE 12Z GEM/12Z UKMET AND 12Z ECMWF ARE A LITTLE WEAKER BUT ARE WELL CLUSTERED AT THIS TIME WITH A TRACK GENERALLY OFF TO THE WEST. WILL PREFER A NON-NAM CONSENSUS AS A RESULT. ...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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