MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1140 PM EST TUE JAN 28 2014 VALID JAN 29/0000 UTC THRU FEB 01/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE TROUGH CROSSING NORTHERN MEXICO...THE GULF OF MEXICO/FLORIDA PENINSULA THURS AND FRI... PREFERENCE: 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE REMNANTS OF A CLOSED LOW THAT HAD DROPPED ACROSS THE NRN BAJA PENINSULA WILL BE WEAKENING INTO A SRN STREAM SHORTWAVE TROUGH THAT WILL GRADUALLY TRAVERSE NRN MEXICO AND THE GULF OF MEXICO THROUGH THURS...BEFORE ARRIVING ACROSS THE FL PENINSULA ON FRI. THE 00Z GFS AND EVENTUALLY THE 12Z GEM GLOBAL BECOME THE MOST PROGRESSIVE WITH THE ENERGY. THE 00Z NAM AND 12Z UKMET ARE THE SLOWEST SOLN. THE 12Z ECMWF SPLITS THE DIFF. OVERALL THERE IS NOT REALLY THAT MUCH MODEL SPREAD...BUT BASED ON ITS PLACEMENT WITHIN THE SPREAD...WILL FAVOR THE 12Z ECMWF. ...UPPER TROUGH/SURFACE LOW EXITING OFF THE EAST COAST ON WED... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS REASONABLY GOOD MODEL AGREEMENT NOW WITH THE SHORTWAVE TROUGH MOVING ACROSS THE EASTERN U.S. AND WITH IT EXITING OFFSHORE ON WED. THE MODELS SHOW GOOD AGREEMENT TOO WITH THE SURFACE LOW GRADUALLY INTENSIFYING OFF THE MID-ATLANTIC COAST AND EXITING OUT TO SEA AWAY FROM NEW ENGLAND. WILL PREFER A GENERAL MODEL COMPROMISE WITH THIS SYS. ...COMPACT UPPER LOW CROSSING SOUTHERN CANADA... ...REINFORCING SHOT OF COLD AIR TO THE NORTHERN TIER... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: AVERAGE THE MODELS AGREE RATHER STRONGLY WITH THE EVOLUTION OF A COMPACT NRN STREAM VORTEX PIVOTING ACROSS THE SRN CANADA THROUGH THE PERIOD. AN ATTENDANT ARCTIC COLD FRONT WILL BE CROSSING DOWN INTO THE NRN U.S. AS WELL...AND SHOULD MOVE THROUGH THE MIDWEST AND GREAT LAKES REGION. THE 00Z NAM TENDS TO BE A BIT SLOWER THAN THE MULTI-MODEL CONSENSUS WITH THE COLD FRONT...AND ALSO IS SEEN AS TRACKING ITS HEIGHT FALLS ACROSS ONTARIO AND ESP QUEBEC A LITTLE MORE QUICKLY BY THE END OF THE PERIOD. DIFFS ARE NOT PARTICULARLY LARGE...BUT WILL PREFER A NON-NAM CONSENSUS ATTM. ...SPLIT FLOW PATTERN IMPACTING THE WESTERN U.S. THROUGH FRI... PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z ECENS MEAN CONFIDENCE: AVERAGE THE MEAN UPPER RIDGE WHICH HAS CONTINUED TO HOLD STRONG ALONG THE WEST COAST IS IN THE PROCESS OF BREAKING DOWN AS MULTIPLE SHORTWAVE IMPULSE ADVANCE IN OFF THE PACIFIC OCEAN. THE INITIAL ENERGY INVOLVING THE NRN STREAM WILL AFFECT THE PAC NORTHWEST ON WED...AND ADVANCE INTO THE INTERMOUNTAIN WEST BY THURS. ALL THE WHILE...A SOUTHWESTWARD EXTENSION OF SHORTWAVE ENERGY/TROUGHING BACK OFFSHORE THE WEST COAST WILL ADVANCE THROUGH CA AND INTO THE FOUR CORNERS REGION BY THURS AND FRI. THE MODELS SHOW A FAIR DEGREE OF STREAM SEPARATION AS THE ENERGY TRAVERSES THE INTERIOR. THERE IS RATHER MINIMAL MASS FIELD SPREAD EARLY ON WITH THE NRN ENERGY TRAVERSING THE NORTHWEST...BUT THE SRN STREAM ENERGY IS IN A BIT MORE DISARRAY. THE 00Z ECMWF AND 00Z NAM ARE A BIT FASTER THAN THE MULTI-MODEL CONSENSUS WITH THE INITIAL HEIGHT FALLS CROSSING CA AND EJECTING INTO THE INTERIOR. SUBSEQUENT SMALLER SCALE SHORTWAVE IMPULSES COMING IN OFF THE PAC OCEAN ARE SEEN AS BEING BIT MORE PROGRESSIVE AND A TAD MORE SHEARED ON THE 12Z ECMWF/12Z UKMET AND TO SOME EXTENT THE 12Z GEM GLOBAL COMPARED TO THE 00Z NAM AND 00Z GFS. THE NCEP MODELS TEND TO FAVOR SOMEWHAT STRONGER SHORTWAVE TROUGHING IMPACTING CA ON FRI...WITH THE NON-NCEP SOLNS SUGGESTING MORE TROUGHING DOWNSTREAM OVER THE FOUR CORNERS REGION. WILL FAVOR THE NON-NCEP CAMP BASED ON A BIT BETTER SUPPORT FROM THE 18Z GEFS MEAN AND 12Z ECENS MEAN. WILL FAVOR A BLEND OF THE 12Z ECMWF AND 12Z ECENS MEAN. ...NORTHERN STREAM TROUGH ARRIVING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST/GREAT LAKES BY FRI/SAT... PREFERENCE: 00Z GFS CONFIDENCE: AVERAGE ADDITIONAL NRN STREAM ENERGY/HEIGHT FALLS WILL DROP DOWN INTO THE NRN PLAINS AND THE UPR MIDWEST ON FRI AND BEGIN DIGGING TOWARD THE GREAT LAKES ON SAT. THE 12Z ECMWF AND 12Z UKMET ARE A BIT MORE PROGRESSIVE THAN THE MULTI-MODEL CONSENSUS WITH THE HEIGHT FALLS...WITH THE 00Z NAM/00Z GFS AND 12Z GEM GLOBAL SLOWER. THE 18Z GEFS MEAN AND 12Z ECENS MEAN SUGGEST THE ECMWF/UKMET SOLNS ARE A LITTLE TOO PROGRESSIVE...AND TEND TO SUPPORT THE GFS SOLN. THE 00Z GFS WILL BE PREFERRED BASED ON THIS STRONGER MODEL CLUSTERING. ...FRONTAL ZONE SETTING UP FROM THE FOUR CORNERS INTO THE SOUTHERN PLAINS AND TN/OH VALLEYS... ...SURFACE LOW EJECTING NORTHEAST TOWARD THE OHIO VALLEY... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET AND 12Z GEM GLOBAL CONFIDENCE: BELOW AVERAGE GIVEN THE AFOREMENTIONED SERIES OF NRN STREAM IMPULSES/TROUGHS CROSSING THE NRN TIER STATES AND SRN CANADA THE NEXT COUPLE OF DAYS...THERE WILL BE THE SWD ADVANCE AND REINFORCEMENT OF A STRONG FRONTAL ZONE ACROSS THE SOUTHERN PLAINS WHICH WILL BE ORIENTED NORTHEAST BY FRI/SAT UP TWD THE OH/TN VLY AREA. THE MODELS INDICATE SOME OF THE ENERGY EJECTING EAST OUT ACROSS THE FOUR CORNERS REGION SHEARING DOWNSTREAM ACROSS THE CNTRL PLAINS AND MIDWEST. THIS SHOULD FOSTER A WAVE OF LOW PRESSURE ALONG THE FRONT. GIVEN THE GENERAL PREFERENCE TO BE MORE PROGRESSIVE WITH THE UPSTREAM PACIFIC SHORTWAVE ENERGY TRAVERSING THE INTERMOUNTAIN WEST...WILL FAVOR THE MORE PROGRESSIVE SFC WAVE DETAILS ALONG THE FRONT DOWNSTREAM. THIS IS CURRENTLY LED BY THE 12Z ECMWF/12Z UKMET AND 12Z GEM GLOBAL. THE 00Z NAM IS SLOWER WITH THE SFC WAVE...AND THE 00Z GFS HAS LITTLE IF ANY DEFINABLE WAVE CENTER BY FRI NIGHT/SAT APPROACHING THE OH VLY. WILL FAVOR THE NON-NCEP CAMP...BUT CONFIDENCE WILL BE LIMITED GIVEN THE COMPLEXITIES OF THE SMALL SCALE SHORTWAVE IMPULSES SHEARING DOWNSTREAM. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON