MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 232 PM EDT SAT MAR 22 2014 VALID MAR 22/1200 UTC THRU MAR 26/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM GLOBAL AND ECMWF ...SHORTWAVE TROUGH DIGGING ACROSS THE GREAT LAKES/OH VALLEY/MID-ATLANTIC ON SUN... ...WEAK SURFACE LOW PRESSURE DEVELOPING ALONG OR JUST OFF THE SOUTHEAST COAST ON SUN... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: AVERAGE THE MODELS CONTINUE TO ADVERTISE A SHORTWAVE TROUGH DROPPING SEWD ACROSS THE GRT LAKES AND OH VLY ON SUN BEFORE THEN ADVANCING ACROSS THE MID-ATLANTIC SUN NIGHT. THE ENERGY WILL BE INTERACTING WITH A FRONTAL ZONE DRAPED OVER THE SOUTHEAST...AND THIS WILL ALLOW FOR AN AREA OF LOW PRESSURE TO DEVELOP ALONG IT INVOF SOUTHEAST COAST OR JUST OFFSHORE ON SUN. THE NAM IS A BIT OF A STRONG OUTLIER WITH THE DIGGING ENERGY WITH THE REMAINING MODELS WELL CLUSTERED. THE STRONGER NAM DOES TO TEND TO CORRESPOND TO A SOMEWHAT STRONGER SFC LOW OFFSHORE THE SOUTHEAST...WITH THE REMAINING MODELS A TAD WEAKER. WILL FAVOR A NON-NAM CONSENSUS. ...DEEP LONGWAVE TROUGH DEVELOPING OVER THE EASTERN U.S. MON AND TUES... ...CYCLOGENESIS OVER THE NORTHEAST GULF OF MEXICO LATE MON... ...RAPIDLY INTENSIFYING SURFACE LOW OFF THE SOUTHEAST/MID-ATLANTIC STATES BY TUES... PREFERENCE: BLEND OF THE 12Z GFS/12Z GEM GLOBAL AND 00Z ECENS MEAN CONFIDENCE: BELOW AVERAGE THE UPR PATTERN BEGINS TO STRONGLY AMPLIFY ENTERING THE BEGINNING OF NEXT WEEK WITH A LARGE POSITIVE HEIGHT ANOMALY SETTING UP ACROSS THE WESTERN U.S. AND AN INCREASINGLY AMPLIFIED EASTERN U.S. LONGWAVE TROUGH WHICH WILL BE ENHANCED BY THE DIGGING OF A WELL-DEFINED SHORTWAVE TROUGH WHICH WILL RACE FROM THE DAKOTAS SEWD INTO THE OH/TN VALLEYS BY EARLY TUES. THIS FEATURE IS OF SIGNIFICANT IMPORTANCE AS IT ALLOWS FOR THE LARGER SCALE TROUGH APPROACHING THE EAST COAST TO BEGIN TAKING ON A NEGATIVE-TILT...AND IT WILL BE INTERACTING WITH A STRONG FRONTAL ZONE OVER THE GULF OF MEXICO AND JUST OFFSHORE THE SOUTHEAST COASTLINE. THE GUIDANCE SHOWS SIGNIFICANT CYCLOGENESIS OCCURRING...WITH LOW PRESSURE INITIALLY DEVELOPING OVER THE NERN GULF OF MEXICO AND THEN INTENSIFYING RAPIDLY OFF THE SOUTHEAST AND MID-ATLANTIC COASTS ON TUES. THE LATEST NAM DEPICTS AN ELONGATED BUT NEGATIVELY TILTED TROUGH BY TUES STRETCHING FROM THE GRT LAKES REGION DOWN TO THE MID-ATLANTIC STATES...BUT TENDS TO BE SLOWER WITH THE NRN PORTION OF THE TROUGH AXIS. IT IS QUITE ENERGETIC WITH IS SHORTWAVE DYNAMICS CROSSING THE OH VLY AND CNTRL APPALACHIANS AND SO MUCH SO THAT IS PLACES A RATHER DOMINANT AREA OF LOW PRESSURE OVER THE OH VLY...WHILE SUGGESTING CONSIDERABLY MORE MODEST CYCLOGENESIS OVER THE NERN GULF OF MEXICO AND OFFSHORE THE EAST COAST BY COMPARISON. THE 12Z GFS/12Z ECMWF/12Z GEM GLOBAL AND 12Z UKMET SHOW MUCH LESS EMPHASIS ON AN OH VLY LOW AND SUPPORT CONSIDERABLE CYCLOGENESIS JUST OFF THE SOUTHEAST COAST BY EARLY TUES...AND WITH RAPID INTENSIFICATION TO OFFSHORE THE MID-ATLANTIC BY WED. THE 12Z GFS IS QUICKER WITH THE LOW CENTER OFF THE EAST COAST COMPARED TO THE 12Z ECMWF...BUT WITH RESPECT TO TIMING THE 12Z UKMET AND 12Z GEM GLOBAL ARE TRENDING TWD A SOMEWHAT FASTER SOLN LIKE THE GFS. THE 12Z UKMET IS THE DEEPEST SOLN OVERALL AND TRACKS ITS LOW CENTER FARTHEST LEFT...WHICH HAS VIRTUALLY NO ENSEMBLE SUPPORT ATTM. THE 12Z GEM GLOBAL IS A LITTLE WEAKER THAN THE 12Z UKMET...FOLLOWED THEN BY THE 12Z GFS AND 12Z ECMWF. IT WAS NOTICED THOUGH THAT THE 12Z GFS MAY BE SUFFERING FROM SOME DEGREE OF FEEDBACK NEAR THE MID-ATLANTIC COAST ON TUES...WHICH HAS SOME IMPLICATIONS FOR ITS QPF DISTRIBUTION...BUT ITS MASS FIELDS OTHERWISE SEEM REASONABLE. THE STRONGEST MODEL CLUSTERING AT THIS POINT NOW TENDS TO FAVOR THE 12Z GFS/12Z GEM GLOBAL AND 00Z ECENS MEAN...WITH THE DETERMINISTIC ECMWF APPEARING TOO SLOW AND PROBABLY TOO FAR SOUTHEAST OFF THE EAST COAST ON TUES. THE 12Z GEFS MEAN FAVORS THE MORE PROGRESSIVE CAMP GFS-LED CAMP. THEREFORE...BASED ON THE LATEST TRENDS AND MODEL CLUSTERING...WILL PREFER A BLEND OF THE 12Z GFS/12Z GEM GLOBAL AND 00Z ECENS MEAN...HOWEVER CONFIDENCE WILL REMAIN LIMITED. ...SOUTHERN STREAM TROUGH POTENTIALLY CUTTING OFF OVER SOUTHERN CALIFORNIA THIS PERIOD... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE AS AN UPR RIDGE BUILDS ACROSS THE WESTERN U.S...THE MODELS DEPICT ENERGY PINCHING OFF UNDERNEATH IT INVOF SRN CA BY LATE SUN AND MON. ON TUES...THE ENERGY WILL BEGIN TO SLOWLY ADVANCE EAST ACROSS THE AZ/NM IN RESPONSE TO A LARGER SCALE TROUGH ADVANCING TWD THE WEST COAST. THE NAM BY THEN BEGINS TO BECOME NOTABLY WEAKER WITH THE TROUGHING AND IS QUICKER TO ADVANCE IT DOWNSTREAM. THE GLOBAL MODELS CLUSTER WELL WITH THEIR MASS FIELDS INVOLVING TIMING AND DEPTH...AND SO WILL PREFER A NON-NAM CONSENSUS ATTM. ...LONGWAVE TROUGH APPROACHING THE WEST COAST BY TUES... PREFERENCE: BLEND OF THE 12Z GFS/12Z GEFS MEAN AND 00Z ECENS MEAN. CONFIDENCE: AVERAGE BY EARLY TUESDAY...A WELL-DEVELOPED CLOSED LOW AND BROADER LONGWAVE TROUGH WILL BE POSITIONED JUST OFFSHORE THE WEST COAST...WITH SFC LOW PRESSURE APPROACHING BRITISH COLUMBIA. ASIDE FROM SOME DIFFS ASSOCD WITH THE SFC LOW PLACEMENT ON TUES...THE MODELS SHOW REASONABLY GOOD AGREEMENT WITH THE LONGWAVE TROUGH DETAILS INVOLVING TIMING AND DEPTH. THE STRONGER MODEL CLUSTERING AND TRENDS TEND TO FAVOR A BLEND OF THE 12Z GFS/12Z GEFS MEAN AND 00Z ECENS MEAN...AND THAT WILL BE THE PREFERENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON