Prognostic Meteorological Discussion
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000 FXUS10 KWNH 191850 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 249 PM EDT TUE SEP 19 2017 VALID SEP 19/1200 UTC THRU SEP 23/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...WITH PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...UPPER TROUGH SWEEPING ACROSS THE NORTHWEST THROUGH TONIGHT... ...ASSOCIATED COLD FRONT EJECTING ACROSS THE NORTHERN PLAINS THROUGH WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODEL DIFFERENCES ON THIS FEATURE HAVE CONTINUED TO DECREASE WITH THE 12Z GFS NOW IN LINE WITH 00Z ECMWF/UKMET/CMC CONSENSUS AS THE COLD FRONT MOVES ACROSS THE NORTHERN PLAINS TO LAKE SUPERIOR WEDNESDAY. THEREFORE A GENERAL MODEL BLEND IS PREFERRED. 19Z UPDATE: GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE 12Z CYCLE. ...SHORTWAVE ENTERING THE PACIFIC NORTHWEST TONIGHT...DEEPENING THE TROUGH OVER THE WEST WED THROUGH FRI... ...SURFACE WAVE DEVELOPMENT OVER THE PLAINS THURS NIGHT/FRI... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE CONSENSUS IS IN THE TROUGH OVER THE WEST AMPLIFYING AS A SHORTWAVE RIDES FROM THE PACIFIC NORTHWEST TONIGHT TO SOUTHERN CALIFORNIA THURSDAY NIGHT. MOVEMENT OF THE EXISTING LOW EAST OF THE SOUTHERN CANADIAN ROCKIES IS NOW LESS...PARTICULARLY IN THE 12Z GFS WHICH HAS TRENDED TO MUCH SLOWER EAST MOVEMENT OF THE LOW CENTER. THIS HAS BROUGHT THE 12Z GFS INTO BETTER CONSENSUS WITH THE 00Z ECMWF/UKMET. THE 00Z CMC IS THE ONLY OUTLIER WITH THE CANADIAN LOW EJECTED MUCH FARTHER EAST BY THURSDAY EVENING. WILL SEE IF THE CMC REMAINS AN OUTLIER WITH THE 12Z CYCLE. SLIGHT DIFFERENCES EXIST IN THE POSITION OF THE SURFACE LOW AND TROUGH THAT DEVELOPS OVER THE NORTHERN GREAT PLAINS THURSDAY NIGHT INTO FRIDAY OWING TO SLIGHT DIFFERENCES IN THE POSITION OF MID-LEVEL FORCING FROM THE UPPER TROUGH OVER THE WEST AND SOUTHERN CANADIAN PRAIRIE UPPER LOW. THE GREATEST DIFFERENCE IS WITH THE 00Z CMC THAT IS SLOWER WITH THE PLAINS LOW/TROUGH DEVELOPMENT GIVEN THE MORE PROGRESSIVE MOVEMENT TO THE CANADIAN LOW. AT THIS TIME A NON-CMC CONSENSUS IS RECOMMENDED. 19Z UPDATE: 12Z CYCLES OF ECMWF AND GFS CONTINUE TO TREND CLOSER TO EACH OTHER WITH PROGRESS OF SOUTHERN CANADIAN PRAIRIE LOW. THE 12Z CMC REMAINS AN OUTLIER TO THE REST OF THE 12Z GUIDANCE. ...HURRICANE JOSE... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC CONSENSUS CONFIDENCE: REFERENCE NHC PRODUCTS THE LATEST (15Z) NHC TRACK OF HURRICANE JOSE IS CLOSE TO A NON-00Z CMC CONSENSUS WITH MINIMAL MODEL SPREAD THROUGH 00Z THURSDAY. SPREAD THEN INCREASES WITH THE CLOCKWISE RECURVE OF JOSE SOUTH/WEST. THE 12Z NAM/GFS TAKE A TIGHTER CURVE WHILE THE 00Z ECMWF IS BROADER/FARTHER EAST. THE OFFICIAL FORECAST LIES BETWEEN THESE CURVES. 19Z UPDATE: BLEND OF 12Z GFS/ECMWF IS CLOSE TO 15Z OFFICIAL TRACK THROUGH 00Z/22. MODEL SPREAD INCREASES LONGITUDINALLY AFTER THIS TIME. THE 12Z GUIDANCE IS GENERALLY WEST OF THE OFFICIAL TRACK...THOUGH RUN TO RUN CONSISTENCY HAS BEEN LOW. THE 12Z GEFS MEAN IS CLOSEST TO THE OFFICIAL TRACK BEYOND 00Z/22. PLEASE REFER TO THE OFFICIAL NHC FORECAST FOR TRACK UPDATES. ...BROAD UPPER TROUGH OVER THE SOUTHEAST AND GULF COAST REGION... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS ALLOW FOR A BROAD AND WEAK UPPER TROUGH TO REMAIN OVER THE SOUTHEAST AND THE GULF COAST STATES WHILE HURRICANE JOSE RECURVES OFF THE NORTHEAST COAST. THE MODELS ARE IN GOOD AGREEMENT WITH THE BROADER DETAILS OF THE TROUGH...SO A GENERAL MODEL BLEND WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml JACKSON/CHENARD $$

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