MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1259 PM EDT SAT MAR 29 2014 VALID MAR 29/1200 UTC THRU APR 02/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ================================================== 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ================================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ================================================== ...WET AND WINDY EAST COAST SYSTEM... PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF PREFERENCE: 12Z NAM ALSO ACCEPTABLE ALTHOUGH NOT DEEP ENOUGH THE GFS/ECMWF/NAM HAVE COME TOGETHER ON THE LARGE SCALE PROGRESSION OF THIS SYSTEM...BUT THEY DIFFER IN SOME MESOSCALE ASPECTS. THE NAM IS CERTAINLY NOT AS DEEP AS THE GLOBAL MODEL CONSENSUS AT THE SURFACE AND ALOFT...SO THE GFS/ECMWF WOULD BE PREFERRED OVERALL...BUT THE NAM MAY STILL BE USEFUL. THE GFS MAY BE TOO AGGRESSIVELY VEERING THE 700 MB WINDS AND CUTTING OFF PRECIPITATION BEHIND A WAVE THAT IT RACES THROUGH NEW ENGLAND EARLY SUNDAY. WITH THE SYSTEM STILL DEEPENING AND UPPER DIFLUENCE REMAINING OVER INTERIOR NEW ENGLAND...WINDS SHOULD MAINTAIN MORE OF AN ONSHORE COMPONENT FAVORABLE FOR CONTINUED PRECIPITATION INTO SUNDAY AFTERNOON. ON THE OTHER HAND...THE ECMWF IS STILL ONE OF THE SLOWER AND WETTER SOLUTIONS FROM SUNDAY AFTERNOON ONWARD...AND BLENDING IT TOWARD THE MORE PROGRESSIVE GFS WOULD PRODUCE A SOLUTION CLOSER TO CONSENSUS REGARDING THESE DETAILS. ...PLAINS/MIDWEST/GREAT LAKES CYCLONE MONDAY/TUESDAY... PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF ALTHOUGH THE ECMWF AND UKMET HAVE BEEN CONSISTENT...THEIR SOLUTIONS CONTINUE TO LAND CLOSE TO THE NORTHERN EDGE OF THE ENSEMBLE ENVELOPE. THE GFS/GEFS HAVE BEEN WEAKER AND FARTHER SOUTH AND EAST WHICH IS CONSISTENT WITH THE GFS BIAS. WPC HAS FAVORED THE ECMWF ENSEMBLE MEAN...ALSO CONSISTENT... AND PREDICTING A TRACK/INTENSITY JUST SLIGHTLY SOUTHEAST/NOT AS INTENSE AS THE ECMWF/UKMET. THE 12Z GFS HELPED SIMPLIFY THE SITUATION...AS IT TRENDED CLOSE ENOUGH TO THE ECMWF ENSEMBLE MEAN THAT WE CAN NOW RECOMMEND A SIMPLE BLEND OF TWO OPERATIONAL MODELS. THE 06Z NAM APPEARS TO HAVE BEEN A BETTER OPTION THAN THE 12Z RUN...WHICH TRENDED MUCH FASTER. THE 12Z NAM IS REMARKABLY FLAT WITH THE UPPER WAVE AS EARLY AS 30 HOURS INTO THE FORECAST OVER THE FOUR CORNERS REGION. ...DEEP CYCLONE APPROACHING CA TUESDAY... ...LEAD SHORTWAVE REACHING THE ROCKIES TUESDAY... PREFERENCE: BLEND OF 06Z GFS WITH 00Z UKMET/CANADIAN THE 00Z ECMWF WAS ON THE FLAT SIDE OF GUIDANCE GOING FROM DAY 3 INTO 4. OVER THE PACIFIC IT ALSO GOES SOMEWHAT OUT OF PHASE WITH THE ECMWF ENSEMBLE MEAN AS EARLY AS DAY 2. THIS APPEARS RELATED TO THE ECMWF PHASING SYSTEMS IN THE ALEUTIANS WHICH APPEARS UNLIKELY BASED ON THE GFS/GEFS AND ECMWF ENSEMBLE MEAN. ALTHOUGH THE IMPACT ALONG THE WEST COAST IS MORE MINIMAL...THE ECMWF FAILS TO CAPTURE THE LEAD SHORTWAVE MOVING INTO THE CENTRAL ROCKIES ON DAY 3. THEREFORE...A CONSENSUS OF THE OTHER GLOBAL MODELS IS PREFERRED. THE UKMET/CANADIAN WERE CLOSER TO THE CONSENSUS POSITION...WITH THE GFS BEING CHARACTERISTICALLY FASTER. THE 06Z GFS WAS NOT AS FAST AS THE 12Z RUN. THE NAM WAS ON THE FAST SIDE WITH THE LEAD SHORTWAVE...BUT NEAR CONSENSUS ALONG THE WEST COAST. THERE ARE NO STRONG OUTLIERS...BUT THE CLUSTER BEST REPRESENTATIVE OF CONSENSUS APPEARS IN OUR PREFERENCE. ...SUBTROPICAL SHORTWAVE APPROACHING FLORIDA LATE MONDAY... PREFERENCE: BLEND OF 12Z NAM/GFS WITH 00Z ECMWF/UKMET THE MOST NOTABLE OUTLIER WAS THE 00Z CANADIAN...BEING LESS DEEP AND LESS WELL DEFINED. OTHERWISE THERE IS LITTLE MODEL SPREAD FOR THIS LOW AMPLITUDE SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... BURKE