MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 200 AM EST FRI NOV 07 2014 VALID NOV 07/0000 UTC THRU NOV 10/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 00Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...HEIGHT FALLS OVER THE SOUTHEAST AND GULF COAST STATES... PREFERENCE: BLEND OF 00Z GFS/ECMWF/CANADIAN CONFIDENCE: AVERAGE A WELL DEFINED SHORTWAVE TROUGH NEARING THE NORTHERN HIGH PLAINS FRIDAY MORNING WILL DIVE TOWARD THE SOUTHEAST CORNER OF THE U.S. THIS WILL KICK THE CLOSED MID LEVEL LOW OVER NORTHERN MEXICO...CAUSING IT TO OPEN...ACCELERATE EASTWARD...AND BECOME ABSORBED IN THE AMPLIFYING NORTHERN STREAM FLOW. THE UKMET HAS SHOWN SIGNIFICANT VARIABILITY WITH EACH CYCLE. THE GFS AND ECMWF HAVE BEEN RELATIVELY MORE STABLE...WHILE RECEIVING A GOOD DEAL OF SUPPORT FROM THEIR RESPECTIVE ENSEMBLES. INFLECTION IN THE HEIGHT FIELD AND CLUSTERING OF THE ENSEMBLES WOULD SUGGEST A DEVELOPING SURFACE LOW OR FRONTAL WAVE AROUND 30 N/74 W AT THE END OF THE SHORT RANGE...10/12Z. THE GFS/ECMWF FIT THIS CONCEPT...AND THE 00Z CANADIAN TRENDED IN LINE WITH THEM. THE NAM HAS CONSISTENTLY PRODUCED SOME OF THE SLOWEST SOLUTIONS SEEN...ALTHOUGH IT IS TRENDING TOWARD THE PACK. ...ARCTIC AIR SLIDING INTO THE NORTHERN U.S... PREFERENCE: BLEND OF 00Z GFS/ECMWF/CANADIAN CONFIDENCE: AVERAGE WITH AN ANOMALOUS RIDGE POPPING UP THROUGH WESTERN NORTH AMERICA TO NEAR THE NORTH POLE...EARLY SEASON ARCTIC AIR WILL SLIDE FIRMLY INTO SOUTHERN CANADA AND THE NORTHERN U.S. THIS WEEKEND. SUB-500 DECAMETER 500 MB HEIGHTS NEAR HUDSON BAY EARLY SATURDAY WOULD REPRESENT AN IMPRESSIVE 3.5 STANDARD DEVIATIONS FROM CLIMATOLOGY. THE ACCOMPANYING 850 MB AIR CROSSING THE U.S. BORDER IS FORECAST WELL BELOW ZERO CELSIUS...BUT NOT SO ANOMALOUS AS THE MID LEVEL HEIGHTS FARTHER NORTH. THE GEFS MEAN AND ECMWF ENSEMBLE MEAN HAVE SHOWN STEADY PERFORMANCE WHILE TRENDING SLIGHTLY DEEPER AND COLDER INTO THE GREAT LAKES AND NORTHERN NEW ENGLAND. WE RECOMMEND THE GFS/ECMWF/CANADIAN BASED ON ENSEMBLE SUPPORT...WHEREAS THE NAM AND UKMET ARE SOMEWHAT WARMER OVER THIS REGION. ...SHORTWAVE DROPPING DOWN FROM BRITISH COLUMBIA BY LATE IN THE WEEKEND... ...ASSOCIATED CYCLOGENESIS IN THE CENTRAL PLAINS STATES... PREFERENCE: BLEND OF 00Z GFS/ECMWF CONFIDENCE: AVERAGE ARCTIC AIR WILL CONTINUE TO BACK ITS WAY DOWN THROUGH THE NORTHERN AND CENTRAL HIGH PLAINS DURING THE APPROACH OF A PACIFIC SHORTWAVE TROUGH. SURFACE CYCLOGENESIS IS FORECAST...CENTERED ON NEBRASKA...BUT WITH THE PRECIPITATION SWATH FARTHER NORTH INTO SOUTH DAKOTA BY 10/12Z. THE MODELS CLUSTER REASONABLY WELL WITH RESPECT TO THE MID LEVEL TROUGH AND THE STRENGTH AND POSITION OF THE SURFACE LOW THROUGH THAT TIME. THERE ARE SOME DIFFERENCES IN THE THICKNESSES...MOST NOTICEABLE IN A NARROW ZONE OVER THE HIGH PLAINS AND THEN ALSO EAST FROM THE LOW ACROSS IOWA AND EASTWARD...AND RELATED TO THE SECTION ABOVE. WHERE THESE DIFFERENCES EXIST...THE ECMWF ENSEMBLE MEAN HAS SHOWN THE GREATEST CONTINUITY. THE 12Z ECMWF AGREED WITH THE MEAN...BUT THE 00Z RUN TRENDED COLDER/MORE AGGRESSIVE WITH THE SOUTHWARD PUSH OF COLD AIR IN THE PLAINS. THE 00Z GFS SHARED THIS TREND. THERE ARE NO OUTLIERS ON THE LARGE SCALE...AND WITH THE NEW GFS/ECMWF SEEING SUPPORT FROM THE GEFS MEAN WE CAN RECOMMEND A SIMPLE GFS/ECMWF BLEND...ALTHOUGH WE ACKNOWLEDGE LESSER CONFIDENCE AS TO THE THERMAL DETAILS GIVEN THE SMALL SCALE TRENDS. ...CYCLONE LIFTING AWAY FROM MAINE BY FRIDAY EVENING... PREFERENCE: BLEND OF THE OPERATIONAL MODELS...LESS WEIGHT ON THE GFS CONFIDENCE: ABOVE AVERAGE WHEN VIEWING THE FULL 00Z SUITE AND OBSERVATIONAL TRENDS THE GFS STILL SEEMS TO ERR ON THE HEAVY SIDE WITH PRECIPITATION OVER MAINE ON DAY 1. OTHERWISE CONSENSUS IS STRONG. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE