MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 PM EST MON FEB 02 2015 VALID FEB 03/0000 UTC THRU FEB 06/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...NEGATIVELY-TILTED TROF/STRONG SURFACE LOW EXITING NEW ENGLAND.. PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE RADAR IMAGERY TONIGHT SHOWS THE LAST BATCH OF SNOWFALL EXITING DOWNEAST ME AS A POTENT SHORTWAVE MOVES OFF THE NEW ENGLAND COAST. THE MODELS SHOW THE ASSOCIATED SURFACE LOW WILL LIFT NORTH OF NOVA SCOTIA BY 03/1200Z WITH SOME MODEST INTENSITY DIFFERENCES. HOWEVER...THIS IS ONLY A SUBTLE DIFFERENCE IN THE FORECAST SO A GENERAL MODEL COMPROMISE IS RECOMMENDED. ...CLOSED LOW EMERGING FROM MX... ...OPEN WAVE CROSSING THE GULF COAST ON WEDNESDAY/THURSDAY... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE WATER VAPOR IMAGERY SHOWED A CYCLONIC CIRCULATION ANCHORING THE SOUTHERN SEA OF CORTEZ WITH ANOMALOUS TRANSPORT DIRECTED ACROSS CENTRAL MX INTO SECTIONS OF TX. THIS CLOSED SYSTEM SHOULD GRADUALLY WEAKEN AS IT MIGRATES TOWARD THE RIO GRANDE VALLEY ON TUESDAY NIGHT. AS THE SHEARING SHORTWAVES MOVE ALONG THE GULF COAST REGION...THE 00Z NAM AND 12Z ECMWF HELP LIFT SOME OF THESE ENERGETICS NORTHWARD UP TOWARD COASTAL NC BY EARLY THURSDAY. WOULD PREFER TO LEAN ON THE MORE SUPRESSED SIGN OF THE EQUATION WHICH IS MORE ALONG THE LINES OF THE 00Z GFS AND 12Z CMC/UKMET. THE 18Z GEFS/21Z SREF MEANS SEEM TO SHOW MOST SUPPORT TOWARD THE 00Z GFS/12Z UKMET SO WILL LEAN FAVOR A BLEND OF THESE TWO DETERMINISITIC MODELS. ...DEEP UPPER TROF MOVING FROM THE UPPER MIDWEST TO NEW ENGLAND ON WEDNESDAY THROUGH FRIDAY... ...ASSOCIATED STRONG BAROCLINIC ZONE... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/12Z CMC FORECAST CONFIDENCE: LOW THE SYSTEM CONSISTING OF A TREMENDOUS AMOUNT OF SPREAD WILL BE NOTED AS STRONG HEIGHT FALLS ENTERING THE UPPER MIDWEST BY EARLY WEDNESDAY. TOWARD THE END OF DAY 3...THE FORECAST SPREAD LOOKS MORE LIKE A DAY 5 FORECAST VERSUS A DAY 3 FORECAST. BY 05/0000Z...TIMING/AMPLITUDE DIFFERENCES ARE EVIDENT WITH THE 12Z ECMWF/ECMWF ENSEMBLE MEAN REMAINING SLOWER THAN THE 18Z GEFS/21Z SREF MEANS. AS TIME PROCEEDS FORWARD...THE 12Z ECMWF SLOWS EVEN FURTHER WHILE AMPLIFYING A DEEP UPPER TROF ACROSS THE GREAT LAKES REGION. THIS HAS SUFFICIENT SUPPORT FROM ITS ENSEMBLE MEAN AS WELL AS THE CORRESPONDING SPAGHETTI PLOTS. ADDITIONALLY...THE 12Z UKMET SHOWS SIGNS OF JOINING THIS SOLUTION DURING THE PERIOD. THE RAMIFICATIONS OF SUCH A FORECAST IS A STRONG CLOSED LOW ANCHORING COASTAL NEW ENGLAND BY 06/1200Z VERSUS THE 00Z NAM/GFS...12Z CMC...AND 18Z GEFS/21Z SREF MEANS WHICH FAVOR A QUICKER/LESS AMPLIFIED SOLUTION. UNLESS SOME 00Z GUIDANCE TRENDS IN THE DIRECTION OF THE AMPLIFIED 12Z UKMET/ECMWF/ECMWF ENSEMBLE MEAN...FEEL THIS EXTREME SOLUTION MUST BE REJECTED. THIS IDEA WAS COORDINATED WITH WPC MEDIUM RANGE WHICH AGREED IN REMOVING THIS SOLUTION. FEEL THE BEST WAY TO RESOLVE THIS FORECAST IS PLAYING RIGHT IN THE MIDDLE OF THE SPREAD AS THE 00Z GFS AND 18Z GEFS/21Z SREF MEANS ARE MUCH QUICKER. A COMBINATION OF THE 00Z NAM/12Z CMC IS THE BEST CENTERPOINT BUT WITH LOW CONFIDENCE AT BEST. ...SERIES OF SYSTEMS AFFECTING THE PACIFIC NORTHWEST... ...PAIR OF DEEP SURFACE CYCLONES APPROACHING THE REGION... PRELIMINARY PREFERENCE: THROUGH DAY 2: BLEND OF THE 18Z GEFS/21Z SREF MEANS...THEREAFTER: 18Z GEFS MEAN FORECAST CONFIDENCE: BELOW AVERAGE GIVEN THE DOWNSTREAM PATTERN FEATURES A SERIES OF TIMING/AMPLITUDE ISSUES...IT IS NOT A BIG SURPRISE THE NORTHWESTERN U.S. IS PLAGUED BY SUCH PROBLEMS AS WELL. THE LARGER DIFFERENCES ARE CONFINED TO DAY 2 WHERE THE 12Z ECMWF/ECMWF ENSEMBLE MEAN ARE SLOWER RELATIVE TO THE QUICKER 00Z NAM/12Z UKMET SOLUTIONS. GIVEN THE SPREAD AT HAND...WILL PLAY IT CONSERVATIVELY FAVORING A BLEND OF THE 18Z GEFS/21Z SREF MEANS. CONFIDENCE IS BELOW AVERAGE WITH THIS PREFERENCE. THEREAFTER...ALL THE MODELS SHOW A SIGNAL FOR HEAVY PRECIPITATION ACROSS THE SHASTA RANGE UP ALONG THE CASCADES AND OLYMPICS. HOWEVER...ALOFT...A SLEW OF DIFFERENCES ARE NOTED WHICH IS TO BE EXPECTED GIVEN THE TRANSITIONING PATTERN. PLAN ON STICKING WITH ENSEMBLE MEANS BUT WILL REMOVE THE 21Z SREF MEAN AS IT BECOMES THE QUICKER OF THE MEANS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER