MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 140 AM EST MON FEB 08 2016 VALID FEB 08/0000 UTC THRU FEB 11/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW STRENGTHENING OFF THE SOUTHEASTERN U.S. COAST SURFACE CYCLONE DEEPENING ALONG THE GULF STREAM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE VERY STRONG OCCLUDED LOW IS NOW WELL DEVELOPED OFF THE CAROLINA COASTLINE DRIFTING EAST...SOME SMALL DISPLACEMENT ERRORS WERE NOTED INITIALLY WITH THE 12Z UKMET BUT STABILIZED AS IT DRIFTS NORTH-NORTHEAST TOWARD THE NE TIP OF NOVA SCOTIA BY 09/12Z TUE... UNDER FAIRLY STRONG AGREEMENT BOTH AT THE SURFACE/ALOFT...WITH THE 00Z NAM/12Z CMC LAGGING EVER SO SLIGHTLY. IT IS AFTER THIS POINT INFLUENCES FROM UPSTREAM DEEPENING CYCLONE WILL HELP TO SHEAR THE SYSTEM VERTICALLY DRAWING THE UPPER LEVELS WEST AND LOW LEVELS SLOWLY TOWARD NEWFOUNDLAND. THE CMC IS DRAWN WEST ALOFT A BIT MORE AND 12Z UKMET LEAST...AT THE SURFACE THE 00Z GFS IS FURTHEST EAST THOUGH THE 18Z GEFS MEAN IS FURTHER EAST. OVERALL THE DIFFERENCE APPEAR MINOR SPECIFICALLY WITH THIS SYSTEM TO SUPPORT AN OPERATIONAL MODEL BLEND BUT WITH SOME INCREASING SPREAD AND INFLUENCES TUES..WILL WEIGHT HEAVIER TO MORE STABLE/INTERNALLY CONSISTENT MODELS OF THE 00Z GFS/12Z ECMWF AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. 07Z UPDATE: THE 00Z UKMET RESOLVED SOME OF ITS INITIAL ISSUES...BUT IS INITIALIZED AS THE DEEPEST OF THE DETERMINISTIC MODELS AND GENERALLY WOBBLES AROUND THE MEAN TRACK OF THE OTHER GUIDANCE BUT NOT DRAMATICALLY TO REMOVE IT. THE 00Z CMC/ECMWF BOTH FURTHER SOLIDIFIED THE PROSPECT OF OPERATIONAL BLEND AT ABOVE AVERAGE CONFIDENCE. BROAD SHORTWAVE DIGGING THROUGH THE UPPER MIDWEST THIS MORNING EVENTUAL CLOSED LOW MIGRATING FROM THE UPPER GREAT LAKES TO THE OH VALLEY PAIR OF SURFACE CYCLONES AFFECTING THE GREAT LAKES AND VA COASTAL LOW AND LINGERING WAKE LOW PRESSURE/SURFACE LOWS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE BROAD BUT EXPANDING UPPER TROF IS STARTING TO SETTLE ACROSS THE GREAT LAKES WITH FAIRLY GOOD MODEL AGREEMENT IN THE INTERNAL CENTER OF THE WAVE AS A WHOLE INCLUDING THE WEAKENING SURFACE REFLECTION. STILL SUBTLE TIMING DIFFERENCE WITH INTERNAL WAVES CONTINUES TO PLAGUE MESOSCALE BUT IMPORTANT IMPACT DETAILS...BUT THIS IS EVEN TRENDING BETTER AS THE 00Z GFS WHICH HAD BEEN GENERALLY FAST WITH THE INTERNAL WAVE LEANING FORWARD AND DEVELOPING THE SURFACE REFLECTION OVER VA AND OUT TO SEA A BIT FASTER THAN MUCH OF THE GUIDANCE SUITE CONTINUES TO TREND A BIT SLOWER WITH THE WAVE BUT ALSO IS MOST WRAPPED UP AND STRONGEST WITH THE SURFACE REFLECTION BY 10/00Z SE OF NOVA SCOTIA. THE 12Z ECMWF WAS ALSO THE SLOWER AND SOUTHERN MODEL GENERALLY WITH A BULK OF ITS ENSEMBLE MEMBERS FURTHER WEST AND ABOUT 3-6HRS SLOWER IN DEVELOPMENT THOUGH HAVING A SIMILAR TRACK TO THE GFS...BUT THE OPERATIONAL MODEL WAS ON THE EASTERN SIDE OF THE ECENS ENSEMBLE PLOT NEARER TO THE REST OF THE GUIDANCE INCLUDING THE GFS/NAM/UKMET. THE 12Z CMC IS ON THE FAR EASTERN FRIDGE OF THE ENSEMBLE PLOT WITH LARGE SPREAD IN ITS ENSEMBLE MEMBERS...IT IS ALSO GENERALLY MUCH WEAKER WITH THE SURFACE REFLECTION AND TENDS TO SHIFT ENERGY TO THE WAKE LOW NEAR CAPE COD ON WED MORNING...OUT OF PHASE WITH MUCH OF THE OTHER GUIDANCE INCLUDING THE ENSEMBLES...MAKING IT LESS DESIRABLE. THE 12Z UKMET IS MUCH MORE STABLE THAN THE CMC AND TRACKS WELL WITH THE GFS/ECMWF/NAM SOLUTIONS INITIALLY BUT BEGINS TO BUCKLE THE TROF A BIT DEEPER INTO THE SOUTHEAST BY WED MORNING AND IS THE FASTEST IN SHIFTING THE WHOLE TROF OUT OF THE EASTERN US BY THE END OF THE PERIOD. THE 00Z NAM TRACKS WELL PARTICULARLY WITH THE SLOWER 12Z ECENS MEAN AND ECMWF THROUGHOUT THE FORECAST PERIOD...AND GIVEN ITS HIGHER RESOLUTION MAY BE A BIT MORE AFFECTIVE IN SOME OF THE MESOSCALE DETAILS BRINGING SOME ADDITIONAL CONFIDENCE IN A BLEND. AS SUCH WILL SUPPORT A 00Z NAM/GFS AND 12Z ECWMF BLEND AT AVERAGE CONFIDENCE OVERALL (THOUGH CONFIDENCE IN THE LARGE SCALE SYNOPTIC SETUP MAY BE CLOSER TO ABOVE AVERAGE). 07Z UPDATE: THE 00Z ECMWF CONTINUES TO PERFORM CONSISTENTLY FURTHER TRENDING TOWARD THE GFS COMPROMISE BUT REMAINS SLIGHTLY WEAKER AND SOUTH WITH THE COASTAL DEVELOPMENT COMPARED TO THE GFS AND 00Z UKMET. THE 00Z UKMET TRENDED A BIT FASTER/DEEPER AND MORE IN AGREEMENT WITH THE GFS SOLUTION YET STILL ON THE EASTERN SIDE OF THE CLUSTER. ALONG WITH THE 00Z GEFS BECOMING EVEN SLOWER THAN THE 00Z GFS...FURTHER SOLIDIFYING THE GFS/ECMWF SOLUTION WITH THIS COASTAL WAVE PUTS THE 00Z NAM ON THE OUTSIDE OF STRENGTHENING AGREEMENT WITH THIS WAVE. THE 00Z CMC TRENDED STRONGER AS WELL BUT REMAINS ON THE WEAK/EASTERN SIDE OF THE GUIDANCE ALMOST WITH THE 00Z NAM. WOULD CONSIDER SWAPPING THE 00Z NAM FOR THE 00Z UKMET TO STRENGTHEN THE BLEND BUT GIVEN SOME ISSUES ALOFT ON QUICKNESS OF EJECTING THE BASE OF THE TROF AT THE END OF THE FORECAST ALONG WITH INCREASING STRENGTH OF AGREEMENT IN THE 12Z ECENS MEAN AND 00Z GEFS/GFS/ECMWF TO KEEP IT OUT THOUGH IT HAS ITS GRACES TO PROVIDE INCREASING CONFIDENCE. AS SUCH FINAL PREFERENCE IN 00Z GFS/ECMWF AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. SHEARING SHORTWAVE BLEEDING INTO THE U.S. NORTHERN PLAINS WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/CMC BLEND CONFIDENCE: AVERAGE A SUBTLE FAST MOVING SHORTWAVE OVERTOPS THE STRONGER WESTERN RIDGE TUESDAY ACROSS THE SW NORTHWEST TERRITORIES...EVENTUALLY DROPPING ACROSS THE SOUTHERN CANADIAN PRAIRIES WITH LIGHT SNOWS INTO THE NORTHERN RED RIVER VALLEY WED EVENING AND EVENTUALLY SHEARING FULLY INTO THE FLOW OVER THE UPPER MIDWEST BY THURS. THE 12Z UKMET IS FLATTER WITH THE WAVE BUT WITH A TIGHTER GRADIENT AFTER OVERTOPPING THE RIDGE IS STRONGER WITH INCREASED QPF AND FASTER TRAJECTORY...ABOUT 12HRS FASTER THAN THE ENSEMBLE MEANS. THE 12Z CMC SURFACE REFLECTION BACK OVER THE DAKOTAS IS QUITE DEEP AND EXPANSIVE OUT OF PHASE WITH OTHER GUIDANCE AND FURTHER WEST THAN EVEN THE EARLIER. THE 00Z NAM DOES EJECT THE WAVE OVER THE TOP OF THE RIDGE UNLIKE ITS PRIOR RUNS (18Z) BUT IS VERY WEAK AND SLOW FAVORING THE 18Z GFS. THE 00Z GFS HOWEVER HAD TRENDED A BIT FASTER NOW NEARING THE 12Z ECMWF SOLUTION/ THE 18Z GEFS/12Z ECENS MEAN ARE IN FAIRLY GOOD AGREEMENT WITH THE 00Z GFS AND ECMWF. AS SUCH WILL BLEND THE 00Z GFS/12Z ECWMF WHICH SHOULD RETAIN SOME OF THE MAGNITUDE BUT STILL REPRESENTING THE GEFS/ECENS MEANS. GIVEN THE WEAKNESS OF THE FEATURE/SHEARING OUT AS WELL AS SPREAD IN TIMING...CONFIDENCE IN THIS BLEND REMAINS ONLY AVERAGE. 07Z UPDATE: THE 00Z UKMET SHIFTED SLOWER TOWARD THE INITIAL PREFERENCE BUT STILL REMAINS FASTER. THE 00Z CMC TRENDED TOWARD STRONG AGREEMENT WITH THE 00Z GFS PARTICULARLY IN TIMING/PLACEMENT OF QPF/SURFACE LOW AND WITH LITTLE CHANGE (MAYBE A BIT WEAKER) IN THE 00Z ECMWF CONSIDER ADDING THE CMC FOR FURTHER CONFIDENCE. AS SUCH A 00Z GFS/CMC/ECMWF BLEND IS PREFERRED BUT CONFIDENCE REMAINS THE SAME FOR SIMILAR REASONING IN SPREAD/WEAK FEATURE. SYSTEMS TRACKING THROUGH THE WESTERN PACIFIC TOWARD BRITISH COLUMBIA/OLYMPIC PENINSULA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS/ECMWF BLEND CONFIDENCE: AVERAGE A STOUT RIDGE REMAINS A MAINSTAY FEATURE FOR MUCH OF THE EARLY TO MIDDLE PART OF NEXT WEEK. MULTIPLE FEATURES DENT THE WESTERN SIDE OF THE RIDGE AS EXTENSIONS OF LARGER GLOBAL CYCLONE OVER THE CENTRAL NORTH PACIFIC. THIS INCLUDES A LEAD WAVE NEARING VANCOUVER ISLAND TUES EVENING/WED AND A SECOND LESS AMPLIFIED WAVE LATE WED/THURS DRIVING MOISTURE FEED MAINLY INTO CENTRAL AND SOUTHERN BC/VANCOUVER ISLAND EVENTUALLY SHIFTING SOUTH FOR GLANCING AFFECTS INTO THURSDAY LEADING TO OROGRAPHIC ASCENT OVER THE OLYMPIC PENINSULA. ADDITIONALLY THESE WAVE PRODUCE SIMILARLY TIMED SURFACE REFLECTIONS---THOUGH WELL OFF SHORE. THE 12Z UKMET IS A BIT MORE AMPLIFIED WITH THE INITIAL WAVE THOUGH FURTHER WEST WITH THE TOP OF THE WAVE/MAIN VORT CENTER...DISPLACING THE SURFACE REFLECTION WELL WEST AS WELL AND IS ALSO MUCH STRONGER WITH THE SECONDARY WAVE/WAKE LOW. OTHERWISE THE TIMING/AMPLIFICATION OF THE WAVES ARE IN STRONG ENOUGH AGREEMENT WITH ENSEMBLE MEANS TO SUPPORT A NON-UKMET BLEND AND THOUGH THE DETERMINISTIC MODELS ARE WELL AGREED UPON FOR THIS ITERATION...DAY TO DAY ENSEMBLE ANALYSIS SHOWS THE HIGH VARIATION WITHIN THE SOLUTION TO KEEP CONFIDENCE ONLY AVERAGE ATTM. 07Z UPDATE: THE 00Z ECMWF TRENDED FASTER WITH THE INITIAL WAVE BUT REMAINS BETTER ALIGNED WITH THE GFS/NAM TO KEEP CURRENT THOUGHT. THE 00Z UKMET REMAINS THE MOST SIGNIFICANT OUTLIER FURTHER WEST WITH THE FIRST WAVE AND IS VERY PROGRESSIVE AND STRONG WITH A THIRD WAVE AT THE VERY END OF THE PERIOD WITH ONLY THE NEW 00Z CMC AGREEING IN TIME/PLACEMENT WHILE THE ECMWF/NAM/GFS ARE STILL UPSTREAM. OTHER SMALL ISSUES ON THE 00Z CMC BEING SLOWER AND LESS AMPLIFIED WITH THE SECOND WAVE PUT IT ON THE OUTER FRINGE OF BEST BUT MODERATE CLUSTERING IN THE NAM/GFS/ECMWF. AS SUCH WILL MAKE THE BLEND NAM/GFS/ECMWF AT AVERAGE CONFIDENCE IN THIS WAVE TRAIN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA