MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 202 AM EST WED FEB 10 2016 VALID FEB 10/0000 UTC THRU FEB 13/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z GUIDANCE EVALUATION INCLUDING FINAL MODEL PREFERENCE AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ LONGWAVE TROF ACROSS THE EASTERN THIRD OF THE U.S LIFTING OUT BY WED ASSOCIATED SURFACE LOWS OVER THE E GREAT LAKES/WEAK LOW SE OF CAPE CAD ISLAND WED MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE SYNOPTICALLY MODEL ARE IN GOOD AGREEMENT WITH SOME SMALL INTERNAL DIFFERENCES IN TIMING/STRENGTH OF THE FEATURES. IN THE WAKE OF THE EXITING CYCLONE NEAR NOVA SCOTIA...A WEAK WAVE IS FORECAST TO DEVELOP ALONG THE LINGERING FRONT. THIS APPEARS TO BE THE REMAINING LARGEST DIFFERENCE. THE 00Z GFS/NAM ARE GENERALLY A BIT STRONGER/FASTER WITH THE ENERGY SWINGING THROUGH NEW ENGLAND AS WELL AS DRAWING SHORTWAVE ENERGY AROUND THE FILLING BASE OF THE LARGER SCALE TROF OVER THE SOUTHERN APPALACHIANS AT THIS TIME... WV LOOP SHOWS A WEAK BAROCLINIC LEAF ALREADY EMERGING TO SUPPORT THIS DEVELOPMENT. THE ENSEMBLE SPREAD WITH RESPECT TO THIS CLUSTER IS ACTUALLY QUITE LARGE WEST TO EAST AT SUCH A SHORT TIME FRAME DRIVEN MAINLY AS THE FEATURE IS VERY WEAK...AT LEAST THE FRONTAL ZONE IS GENERALLY PLACED WELL. THE 00Z GFS IS MOST DRAMATIC WITH A LARGE SHIFT FASTER/EAST OF THE BEST CLUSTER WITH THIS LOW. THE 00Z NAM/12Z ECMWF ARE MORE CENTRALLY LOCATED WITH THE 18Z GEFS/12Z ECENS MEAN...WHILE THE 12Z CMC/UKMET ARE MORE STRUNG OUT AND PLACE MANY SMALLER WEAKER LOWS FROM THE HUDSON CANYON THROUGH GEORGES BANK OCEANIC ZONES ON WED MORNING. STILL WILL FAVOR AN OPERATIONAL MODEL BLEND...BUT GIVEN THE SPREAD OF THESE INTERNAL DIFFERENCES THAT WILL HAVE AFFECTS ON SENSIBLE WEATHER CONFIDENCE IS ONLY AVERAGE ON THIS LARGER/ALL ENCOMPASSING BLEND. 07Z UPDATE: LITTLE CHANGE SEEN IN 00Z RUNS OF THE UKMET/CMC AND ECMWF EXCEPT FOR SLIGHTLY BETTER SURFACE LOW CLUSTERING WED INTO THURS...TO CONTINUE OPERATIONAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. WEAK WAVE AND LOW MOVING ACROSS THE NORTHERN/CENTRAL PLAINS INTO THE MS VALLEY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE SMALL DIFFERENCES IN SURFACE LOW PLACEMENT EXIST TIME TO TIME WITHIN THE OPERATIONAL MODEL SUITE BUT ADJUST BACK TO THE AVERAGE CLUSTER WITH THE NEXT TIME STEP...ALL GENERALLY MINOR TO CONTINUE AN OPERATIONAL MODEL CONSENSUS WITH THIS WAVE AT ABOVE AVERAGE CONFIDENCE. ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT LAKES/ARROWHEAD OF MN FRI MORNING AND ASSOCIATED SURFACE LOW ACROSS SE ONTARIO/NEW ENGLAND SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: ABOVE AVERAGE IN THE WAKE OF THE FILLING LARGE SCALE TROF ACROSS THE EASTERN U.S...A STRONG WAVE DEEPENING ACROSS THE NORTH POLE WILL DROP SOUTH AND DEEPEN THE ARCTIC VORTEX BUILDING A DEEP POOL OF ARCTIC COLD ACROSS HUDSON BAY THURS AND JAMES BAY BY FRIDAY MORNING. OVERALL THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE OVERALL SETUP INVOLVING THIS ARCTIC UPPER LOW AND ARCTIC SURFACE HIGH MOVING TOWARDS THE NORTHERN PLAINS INCLUDING TIGHTLY PACKED ENSEMBLE MEMBERS AROUND THE SOLUTIONS...THIS INCLUDES A SLOWING OF THE GFS/GEFS AND QUICKENING OF THE ECWMF/ECENS AS A WHOLE. IF TO BE VERY PICKY WITHIN THE OVERALL GUIDANCE...THE MODELS FOLLOW A TRADITIONAL SETUP/BIAS...THE UKMET LEANS FORWARD/FASTER FOLLOWED BY THE GFS THEN THE ECMWF WITH THE NAM AND CMC LAGGING THE MOST. THE CMC'S LAG IS MOST DRAMATIC THOUGH BY FRIDAY EVENING/SAT MORNING WHEN AN INTERNAL CORE VORT LOBE LAGS IT OWN MEAN HOLDING UP THE INNER CORE AND RESOLVING TROUGHING OVER NE ONTARIO BUT ALSO RESULTING IN A LAGGED SURFACE REFLECTION OVER THE GREAT LAKES/NEW ENGLAND. THIS LAG IS SUPPORTED ALOFT BY THE 00Z NAM BUT NOT DOES NOT RESOLVE ITSELF IN THE LOWER LEVELS OR WITHIN 21Z SREF...LEADING TO A BIT OF CONCERN IN USING IT IN THE BLEND. AS SUCH WILL FAVOR A NON-CMC BLEND PARTICULARLY AFTER 12/18Z AT ABOVE AVERAGE CONFIDENCE GIVEN THIS IS QUITE SMALL DETAIL DIFFERENCE AT DAY 3. 07Z UPDATE: 00Z CMC WAS A BIT WEAKER OVERALL A TREND TOWARD OTHER GUIDANCE BEST REFLECTED WITHIN THE SURFACE REFLECTION BUT REMAINED SLOW/LAGGED WITH THE TROF OVER ONTARIO AFTER 12/12Z...AND LITTLE CHANGE WITH THE 00Z UKMET/ECMWF TO RETAIN A NON-CMC BLEND AT ABOVE AVERAGE CONFIDENCE PARTICULARLY AFTER 12/12Z. SHORTWAVE ENTERING PACIFIC NORTHWEST WEDNESDAY RAPIDLY DIVING SOUTHEAST INTO THE BASE OF THE EAST COAST TROF INTO FRI AND OFFSHORE EARLY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE SHORTWAVE ENERGY FROM THE BASE OF A NEGATIVE TILT TROF CURRENTLY DEFINED IN WV NEAR 40N137W WILL GLANCE THE PACIFIC NORTHWEST...SLIGHT TIMING DIFFERENCES WILL LEAD SPREAD WITH WHERE THE ENERGY WILL BE DRAWN THROUGH THE LARGE SCALE RIDGING ACROSS THE ROCKIES. HOW AND WHERE WILL DETERMINE THE LENGTH AND STRENGTH OF THE RESULTANT SHEARED SHORTWAVE THAT WILL RAPIDLY MOVE THROUGH THE GREAT PLAINS AND CENTRAL MO RIVER VALLEY FRIDAY MORNING. ADDITIONALLY...THIS WILL ALSO LEAD TO DIFFERENCES IN AMOUNT OF INFLUENCE OR PHASING WITH THE BASE OF THE ARCTIC TROF DROPPING OUT OF MANITOBA. OBVIOUSLY THERE IS A POTENTIAL FOR LARGE SPREAD DUE TO THE LENGTH/CONSOLIDATION OF THE SHEARED ENERGY AS WELL AS STRENGTH...ALL OF WHICH PLAY A ROLE IN THE EVENTUAL COASTAL SURFACE CYCLOGENESIS FRIDAY EVENING. THE TREND IS FOR MORE ENERGY TO BE SHED INTO THE RIDGE...WHICH HAS SEEN A GENERAL TREND TOWARD A DEEPER SURFACE REFLECTION ON DAY 3 WITH AN INCREASE IN ENSEMBLE MEMBERS DEVELOPING A CYCLONE AND A TREND TOWARD A DEEPER LOW AS SEEN IN THE 00Z NAM/GFS AND 12Z UKMET/ECMWF. THE 12Z CMC INJECTED THE LEAST ENERGY AND WAS GENERALLY FASTER AND WEAKER OVERALL...AWAY FROM THIS TREND. THE 12Z ECMWF WAS SLOWEST AND MORE PHASED ROUNDING THE BASE OF THE TROF FRIDAY INCREASING DIVERGENCE ALOFT FOR BETTER/STRONGER SURFACE CYCLOGENESIS...AND IS ON THE SOUTHEAST FRINGE OF THE 12Z ECENS MEAN AS WELL AS SOUTH OF THE BETTER CLUSTERED UKMET/NAM/GFS...WHICH ARE TIGHT TO THE 18Z GEFS MEAN AND THE OVERALL TREND. STILL GIVEN ALL THE DIFFERENCES/SPREAD POSSIBLE WITH JUST SUBTLE TIMING/PLACEMENT/INJECTION DIFFERENCES UPSTREAM...THE ECMWF MAY BE ON THE BEST TRAJECTORY AND NOT OUT OF THE REALM OF POSSIBILITIES. AS SUCH WILL SUPPORT A NON-CMC BLEND AT AVERAGE CONFIDENCE. 07Z UPDATE: THE 00Z ECMWF TRENDED A BIT FASTER AND LESS PHASED WITH THE ARCTIC LOW TROF...WHICH RESULTED IN BETTER AGREEMENT WITH THE 00Z GFS EVEN OUTPACING IT SLIGHTLY WITH A MORE MODEST AND FURTHER NORTH SURFACE REFLECTION SIMILAR TO THE 00Z NAM/UKMET...AND WITH LITTLE CHANGE IN THE 00Z CMC STILL BEING MUCH WEAKER THAN OTHER GUIDANCE...WILL CONTINUE A NON-CMC BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. DEEPER LARGE SCALE TROF APPROACHING NORTHWEST LATE FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z CMC/*12Z* ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE RUN TO RUN ENSEMBLE SPAGHETTI PLOTS SHOW A SIGNIFICANT TREND AWAY FROM A PRONOUNCED TROF ENTERING THE PACIFIC NORTHWEST FRIDAY INTO SATURDAY BUT A FILLING ONE TRENDING FLATTER AND FASTER WITH EACH 12HR CYCLE. THIS IS GENERALLY LEAD BY ECMWF OPERATIONAL LAGGED SLIGHTLY BY THE ECENS MEAN. THE GFS/GEFS WERE SLOWEST TO TREND THIS WAY BUT HAVE CONSIDERABLY FLATTENED WITH TIME TO HAVE FAIRLY GOOD AGREEMENT WITH THE CMCE/CMC UKMET AND NAM WITH THE 12Z CYCLE. HOWEVER THE 12Z ECMWF MAY BE A SHADE TOO AGGRESSIVE AS THE LEADING PORTION OF THE WAVE IS VERY EFFECTIVE (PERHAPS TOO EFFECTIVE) IN DAMPENING THE WELL ESTABLISHED WESTERN RIDGE ALLOWING IT TO BE GENERALLY FAST ACROSS HIGH PLAINS IN LEE OF THE NORTHERN ROCKIES WITH ASCENT/QPF. ALL OTHER MODELS TO DAMPEN THE RIDGE BUT ONLY THE 12Z CMC WAS AS AGGRESSIVE AS THE 12Z ECMWF...THIS INCLUDES THE 12Z ECENS MEAN. THE 12Z UKMET IS MOST AMPLIFIED BY THE END OF THE FORECAST PERIOD BUT QUICKLY MOVES OUT OF PHASE WITH OTHER GUIDANCE INTO DAY 4 WITH A STRONGLY AMPLIFIED TROF...MAKING IT LESS DESIRABLE. THE 00Z GFS DID TREND A BIT MORE AMPLIFIED WITH THE RIDGE BUT BRINGS THE KICKER/BACK EDGE OF THE BROADER WAVE INTO THE NORTHWEST IN GOOD TIMING OF THE ECMWF. THE 00Z NAM IS SIMILAR TO THE GFS BUT LESS AMPLIFIED. THESE ARE SUPPORTED BY THE GEFS. TO BEST REPRESENT THESE MORE FAVORABLE MEANS WILL BLEND THE 00Z NAM/GFS AND 12Z ECMWF AT AVERAGE CONFIDENCE. 07Z UPDATE: THE 00Z CMC/ECMWF CONTINUE THE TREND OF FLATTENING THE RIDGE AND DAMPENING THE TROF AS IT COMES ASHORE EVEN LEADING THE WAY OF THE 00Z CMC OUTPACING IT BY 12Z SAT. THE 00Z CMC ACTUALLY TRENDED A BIT SLOWER THAN THE 12Z RUN...NEARER BUT NOT AS SLOW AS THE 12Z ECENS MEAN. THE 00Z UKMET ALSO KEPT WITH ITS AMPLIFIED SOLUTION NEAREST THE 00Z GFS AND ALSO RESULTING IN THE LARGE SPLIT FROM OTHER GUIDANCE ON DAY 4/5. THIS CONTINUES TO INCREASE THE OVERALL SPREAD IN THE MODEL SOLUTIONS WEAKENING THE INITIAL PREFERENCE OF THE NAM/GFS/ECMWF. THE 00Z GEFS PROVIDES NO REAL HEDGE EITHER...STRONGLY SUPPORTING THE OPERATIONAL GFS. THE BEST DETERMINING FACTOR MAY BE SIDING WITH THE TREND...WHICH CONTINUES IN THE ECMWF FAVOR BUT NOT AS DRAMATIC AS THE 00Z RUN. AS SUCH WILL FAVOR A 00Z CMC/*12Z* ECMWF BLEND TO BEST REPRESENT THE 12Z ECENS MEAN WHICH MAY BE THE BEST SOLUTION IF AVAILABLE TO BLEND IF AVAILABLE. CONFIDENCE SHIFTS FROM AVERAGE TO SLIGHTLY BELOW AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA