MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 307 AM EDT WED MAY 21 2014 VALID MAY 21/0000 UTC THRU MAY 24/1200 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. ============================================== ...CLOSED LOW IN THE SOUTHWEST... PREFERENCE: OPERATIONAL MODEL CONSENSUS WITH DECREASING WEIGHT ON THE NAM CONFIDENCE: ABOVE AVERAGE FOR SEVERAL DAYS THIS SYSTEM HAS BEEN CHARACTERIZED BY FAIRLY STRONG OPERATIONAL MODEL CONSENSUS AND MILD FLUCTUATIONS FROM RUN TO RUN. THE UKMET HAD BEEN SLIGHTLY SLOWER AND SOUTHWEST OF CONSENSUS...BUT THE 00Z RUN TRENDED INTO PHASE WITH THE REST OF THE MODELS. THE NAM PREDICTS A BIT MORE EXPANSIVE CLOSED LOW...WITH STRONGER HEIGHT FALLS OVER NE AZ/NW NM ON DAY 3. IT ALSO BLEEDS HEIGHT FALLS AND ASSOCIATED CONVECTION FARTHER EAST INTO OK/TX. OVERALL THE NAM FORECAST IS NOT UNREASONABLE...BUT GIVEN IT IS ON ITS OWN AND USUALLY DOES NOT PERFORM WELL ON DAY 3...WE RECOMMEND STEERING AWAY FROM IT AT THAT TIME. ...EASTERN/NORTHEASTERN U.S... PREFERENCE: BLEND OF 00Z GFS/ECMWF CONFIDENCE: AVERAGE THE 00Z NAM/GFS/ECMWF SHOW GOOD AGREEMENT HERE...AND HAVE MORE ENSEMBLE SUPPORT THAN THE SLOWER/DEEPER UKMET AND CANADIAN. AT SMALLER SCALES...THE NAM IS SLIGHTLY FASTER THAN THE ECMWF/GFS TO MOVE A SHORTWAVE OFFSHORE OF THE MID ATLANTIC...AND IT HOLDS DEEPER CYCLONIC FLOW AND LOWER HEIGHTS BACK INLAND. ENSEMBLE TRENDS FAVOR SOMETHING MORE LIKE THE GFS/ECMWF. MODELS ARE STRUGGLING TO DEPICT THE UPSTREAM SHORTWAVE RIDGING IN CANADA VERY CONSISTENTLY. THE GFS AND GEFS MEAN APPEAR FAST TO MOVE A TROUGH ACROSS HUDSON BAY...WHICH BUILDS SHORTWAVE RIDGING SOUTHEASTWARD INTO UPSTATE NEW YORK. THE ECMWF HAS MORE MULTI-CYCLE ENSEMBLE SUPPORT IN THIS RESPECT...WITH SHORTWAVE RIDGING HOLDING BACK ACROSS NORTHEAST ONTARIO...AND WEAK TROUGHING APPROACHING NEW YORK ON DAY 3. ...SHORTWAVE TROUGH INFLUENCING THE PACIFIC NORTHWEST/NORTHERN ROCKIES FRIDAY... PREFERENCE: BLEND OF 00Z GFS/ECMWF/CANADIAN CONFIDENCE: AVERAGE MODELS ARE SIMILAR IN TIMING THIS WAVE...ALTHOUGH THE 00Z NAM WAS SLIGHTLY FAST AND A BIT DEEPER THAN CONSENSUS. THE UKMET HAS ALSO PRODUCED DEEPER SOLUTIONS...AND ALTHOUGH THE 00Z RUN TRENDED AWAY FROM THIS...IT WAS STILL ON THE DEEPER SIDE OF THE ENSEMBLE SPREAD. THE 12Z ECMWF WAS ONE OF THE FLATTEST SOLUTIONS HERE...BUT THE 00Z RUN FELL MORE IN LINE WITH THE GFS AND CANADIAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE