MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 247 PM EDT TUE JUN 03 2014 VALID JUN 03/1200 UTC THRU JUN 07/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 12Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...EASTERN U.S... ...INCLUDING POTENT GREAT PLAINS SHORTWAVE EMERGING THIS EVENING... PREFERENCE: BLEND OF 12Z GFS/CANADIAN...SUPPORTED BY THE 12Z GEFS MEAN CONFIDENCE: AVERAGE THE QUASI-PERMANENT TROUGH OVER THE NORTHEAST U.S. WILL SEE A MERGER OF TWO BROAD UPPER LOW CENTERS THROUGH THURSDAY. A LOW AMPLITUDE BUT POTENT SHORTWAVE WILL EJECT ACROSS THE CENTRAL PLAINS STATES TODAY AND ROUND THE BASE OF THE NORTHEASTERN TROUGH BY THURSDAY...PRODUCING A SURFACE LOW AND FRONTAL WAVE ALONG THE NEW ENGLAND COAST. THE OPERATIONAL MODELS HAVE BEEN A LITTLE UNSTEADY FROM RUN TO RUN...WITH FEEDBACK FROM CONVECTION OVER THE MIDWEST AND THE OHIO VALLEY REFLECTED IN THE MODEL SURFACE FORECASTS. THE 00Z ECMWF APPEARED TO SUFFER FROM FEEDBACK...AND PREDICTED A DEEPER SURFACE LOW MOVING ALONG MUCH MORE QUICKLY THAN CONSENSUS. THE 12Z RUN SLOWED DOWN...BUT IS STILL FASTER THAN THE GLOBAL MODEL CONSENSUS. ENSEMBLE SURFACE LOW PLOTS SHOW SOME CONVERGENCE TOWARD THE TRACK SEEN IN THE GFS...OR JUST SLIGHTLY NORTH...AS IN THE 12Z GEFS MEAN. THE GFS HAS BEEN FAIRLY CONSISTENT AT THE SURFACE DATING BACK TO THE 02/12Z CYCLE...AND ITS UPPER LEVEL FORECAST SEEMS MORE REASONABLE NOW...HAVING SLOWED AND DEEPENED. THE GFS IS ALSO SUPPORTED RATHER WELL BY THE 12Z CANADIAN. THE UKMET WAS SIMILAR TO THESE TWO MODELS NEAR THE SURFACE...BUT WAS NOT AS DEEP NOR AMPLIFIED ALOFT. THE NAM HAS DEMONSTRATED POOR RUN TO RUN CONTINUITY. ALTHOUGH THE SURFACE FORECAST APPEARS IMPROVED IN THE 12Z NAM...ITS UPPER LEVEL FORECAST FEATURES A NUMBER OF SHORTWAVE DEPTH AND TIMING AT ISSUES THAT EVENTUALLY LEAD TO A MUCH SLOWER AND DEEPER TROUGH IN THE NORTHEAST BY DAY 3. ...WESTERN SHORTWAVE REACHING THE CENTRAL/NORTHERN PLAINS THURSDAY MORNING... PREFERENCE: BLEND OF 12Z GFS/ECMWF/UKMET CONFIDENCE: AVERAGE THIS TROUGH WAS ENTERING THE NORTHERN ROCKIES TODAY...AND WILL CONTINUE EASTWARD AS A RELATIVELY LOW AMPLITUDE WAVE...HELPING TO FOSTER CONVECTION AS IT GOES. THE NAM IS FLAT AND VERY FAST WITH THIS WAVE...AND IS DISCOUNTED BY 05/12Z. THE GLOBAL MODELS SHOW GENERAL AGREEMENT...THOUGH THE CANADIAN CONTINUES SOMEWHAT SLOW AND DEEP RELATIVE TO THE OTHER THREE. ...TROUGHING OVER THE WEST THU/FRI... ...FRONT DROPPING INTO THE NORTHERN ROCKIES... ROCKIES PREFERENCE: BLEND OF THE 12Z GLOBAL MODELS SOUTHWEST PREFERENCE: BLEND OF 12Z ECMWF/CANADIAN CONFIDENCE: AVERAGE THE NAM APPEARED TOO FAST IN THE NORTHERN STREAM...AND WAS TOO WEAK IN THE SOUTHWEST...INDICATING MUCH WARMER HEIGHTS THAN THE CONSENSUS FORECAST. THE GLOBAL MODELS SHOWED FAIR AGREEMENT. THE GFS IMPROVED UPON ITS 00Z RUN BY LOWERING HEIGHTS OVER THE SOUTHWEST...BUT THE ECMWF AND CANADIAN APPEAR TO DO A BETTER JOB HANDLING A DEPRESSION IN THE HEIGHT FIELD LEFT BEHIND BY A LOW OFF OF CALIFORNIA WHICH IS REABSORBED IN THE FLOW BY THURSDAY EVENING. IN THE NORTHERN STREAM...THE GLOBAL MODELS NOW AGREE AT THE SURFACE AND ALOFT...BUT CONFIDENCE IS NO GREATER THAN AVERAGE GIVEN THE RUN TO RUN FLUCTUATIONS THAT ARE STILL OCCURRING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE