MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1224 PM EST TUE FEB 09 2016 VALID FEB 09/1200 UTC THRU FEB 13/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GUIDANCE EVALUATION INCLUDING INITIAL 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/THE MID-ATLANTIC COAST TUESDAY/WEAK LOW S OF LONG ISLAND WED MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL CONSENSUS CONFIDENCE: AVERAGE MODELS REMAIN IN PRETTY GOOD AGREEMENT WITH THE TROUGH AS IT BEGINS TO FILL AND LIFT TO THE NORTH. THE SURFACE LOW CURRENTLY FAR OFF THE MID ATLANTIC COAST WILL MOVE NORTHEAST AND STAY WELL SOUTHEAST OF NEW ENGLAND. HOWEVER WILL HAVE TO WATCH FOR POTENTIAL WEAK LOW DEVELOPMENT BEHIND THIS LOW AS ADDITIONAL SHORTWAVE ENERGY MOVES FROM NJ TO SOUTH OF LONG ISLAND ON WEDNESDAY. ENSEMBLE LOW PLOTS SHOW EVEN MORE SPREAD IN THE 0Z GUIDANCE THAN YESTERDAYS 12Z RUNS WITH THIS SYSTEM...KEEPING IT A LOW CONFIDENCE FORECAST. THERE IS MORE SUPPORT IN THE 0Z ENSEMBLES FOR THE POTENTIAL OF A SLIGHTLY STRONGER AND FURTHER WEST LOW...WHICH WOULD HAVE SNOW IMPACTS FOR LONG ISLAND INTO SOUTEHRN NEW ENGLAND. THE NEW 12Z GFS HAS JOINED THE STRONGER/WEST GROUP TO JOIN THE GEM AND UKMET. THIS SEEMS TO TRACE BACK TO THE STRENGTH OF THE SUBTLE SHORTWAVE ENERGY AS IT EXITS THE COAST EARLY WEDNESDAY. HOWEVER A COMPARISON OF THE 06Z AND 12Z GFS SHOWS VERY SIMILAR INITIAL CONDITIONS WITH THIS WAVE...WITH DIFFERENCES NOT REALLY APPEARING UNTIL 12Z-18Z WEDNESDAY. THUS APPEARS MORE LIKELY TO BE MORE OF THE INNER DYNAMICS/PHYSICS WITHIN THE MODEL RESPONSIBLE FOR THE CHANGE. OVERALL THIS ASPECT OF THIS TROUGH REMAINS LOW CONFIDENCE...WITH THE ECMWF REMAINING WEAKER AND EAST AND THE NAM KIND OF IN BETWEEN. HARD TO IGNORE THE RECENT TREND TOWARDS THE STRONGER/WEST/WETTER SOLUTIONS. FOR NOW WILL PREFER A GENERAL MODEL CONSENSUS SOLUTION...AS CAN NOT COMPLETELY RULE OUT THE FURTHER EAST SOLUTIONS SUCH AS THE ECMWF AND OLDER GFS RUNS. THE 12Z UKMET APPEARS TOO FAR WEST...BUT CLOSE ENOUGH TO BE INCLUDED IN ANY BLEND AT THIS TIME. AGAIN WHILE MODELS ARE IN GOOD AGREEMENT ON THE LARGER SCALE EVOLUTION...THERE ARE ALSO SOME DIFFERENCES WITH A POTENTIAL WEAK LOW DEVELOPMENT OFF THE MAINE COAST...DUE TO DIFFERENCES IN THE HANDLING OF SUBTLE SHORTWAVE FEATURES WITHIN THE TROUGH. LOWER CONFIDENCE ON THESE DETAILS AND WILL CONTINUE TO JUST PREFER A GENERAL CONSENSUS SOLUTION FOR NOW. ARCTIC CUT-OFF/COLD SURGE ENTERING THE NORTHERN GREAT LAKES/ARROWHEAD OF MN FRI MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL CONSENSUS CONFIDENCE: SLIGHTLY 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. AS CAN BE EXPECTED THERE ARE MINOR DETAIL DIFFERENCES IN BOTH THE POSITION AND DEPTH OF THE LOW/TROUGH...BUT ALL AVAILABLE DETERMINISTIC GUIDANCE SEEMS WELL WITHIN THE ENSEMBLE SPREAD FOR THIS SYSTEM. FOR THAT REASON WILL CONTINUE TO FAVOR A GENERAL MODEL CONSENSUS SOLUTION. WEAK WAVE AND LOW MOVING ACROSS THE NORTHERN/CENTRAL PLAINS INTO THE MS VALLEY TUE/WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL CONSENSUS CONFIDENCE: ABOVE AVERAGE CONTINUE TO SEE GOOD AGREEMENT AMONG THE GUIDANCE WITH THE SHORTWAVE DIVING SOUTHEAST INTO THE NORTHERN PLAINS ALONG THE EASTERN EDGE OF THE PACIFIC RIDGE...AND THE ASSOCIATED SURFACE LOW FORMING NEAR AN AREA OF STRONG LOW/MID LEVEL FRONTOGENESIS. THE 0Z ECMWF REMAINS A BIT QUICKER THAN THE CONSENSUS...BUT IS CLOSE ENOUGH TO THE OTHER GUIDANCE TO CONTINUE TO PREFER A GENERAL MODEL CONSENSUS. DEEPER LARGE SCALE TROF APPROACHING NORTHWEST LATE FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM/GFS AND 0Z ECMWF CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE WILL CONTINUE WITH THE NAM/GFS/ECMWF PREFERENCE. THE 0Z UKMET REMAINS MORE ON THE OUTER EDGE OF THE ENSEMBLE SPREAD AND SEEMS TO REPRESENT A LESS LIKELY SOLUTION...WITH PRETTY GOOD CONTINUITY SEEN IN THE GEFS AND ECMWF ENSEMBLE MEMBERS. THE 0Z GEM IS CLOSER TO THE BETTER ENSEMBLE CLUSTERING BUT STILL A BIT QUICKER WITH THE WAVE AND ALSO WEAKER WITH WEST COAST RIDGE. SHORTWAVE ENTERING PACIFIC NORTHWEST WEDNESDAY...DIVING SOUTHEAST INTO THE BASE OF THE EAST COAST TROUGH INTO FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS AND 0Z ECMWF/GEM CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM AND OZ UKMET ARE A BIT FURTHER SOUTH WITH THIS WAVE MOVING INTO THE PACIFIC NORTHWEST ON WEDNESDAY AND WEAKER/FLATTER WITH THE WEST COAST RIDGE IT IS MOVING INTO. THIS ALLOWS THE WAVE TO MORE QUICKLY ROUND THE TOP OF THE RIDGE...AND REMAIN A BIT STRONGER AS IT THEN DIVES SOUTHEAST TOWARDS THE SOUTHEASTERN PORTION OF THE COUNTRY BY FRIDAY. STILL SOME MINOR DIFFERENCES WITHIN THE ECMWF/GFS/GEM SOLUTIONS...BUT THEY SEEM TO BE MORE REPRESENTATIVE OF THE BETTER CLUSTERING AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD