MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1223 AM EST TUE FEB 02 2016 VALID FEB 02/0000 UTC THRU FEB 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 0Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SURFACE LOW TRACKING NORTHEAST INTO THE GREAT LAKES BY WED AND COLD FRONT MOVING THROUGH THE EAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: ABOVE AVERAGE MODELS REMAIN IN GOOD AGREEMENT ON THE LARGE SCALE WITH THIS SYSTEM. THE GFS HAS SLOWED DOWN FROM ITS RUN LAST NIGHT...AND IS NOW IN LINE WITH THE TIMING SEEN IN THE OTHER DETERMINISTIC GUIDANCE WITH REGARDS TO THE SURFACE LOW MOVING INTO THE GREAT LAKES. DESPITE THE SYNOPTIC AGREEMENT THERE ARE SOME MINOR DIFFERENCES STILL WITH REGARDS TO THE QPF DISTRIBUTION WITH THE SYSTEM...LIKELY DUE TO SMALL MESOSCALE DIFFERENCES IN HOW THE MODELS HANDLE CONVECTION AND THE EVOLUTION OF PRECIPITATION SHIELDS. THE CURRENT WPC PREFERENCE FOLLOWS CLOSEST TO A 0Z GFS AND 12Z HIGH RES ARW SOLUTION...WHICH LIES BETWEEN THE NORTHERN NMMB AND SOUTHERN ECMWF/GEM. THE 0Z GFS CONTINUES TO OUTPACE THE OTHER GUIDANCE WITH THE COLD FRONTAL PROGRESSION INTO THE EAST COAST THROUGH WEDNESDAY. THE 18Z GEFS MEAN MAY BE A TOUCH SLOWER THAN THE DETERMINISTIC GFS...AND THE GFS HAS TRENDED SLIGHTLY SLOWER. ALSO...GIVEN THE USUAL QUICK BIAS OF THE GFS...AND THE FACT THAT ALL THE OTHER DETERMINISTIC GUIDANCE IS SLOWER WITH THE FRONT...THINK THE FAST GFS REPRESENTS A LESS LIKELY SOLUTION. ALSO THE GFS DRY BIAS FROM THE LOWER MS VALLEY EAST INTO THE TN VALLEY AND SOUTHEAST IS QUITE APPARENT. THUS IN GENERAL THE GFS IS CONSIDERED LESS USEFUL WITH THE FRONTAL ASPECT OF THIS SYSTEM...WITH MORE WEIGHT TOWARDS THE ECMWF/UKMET/GEM. SHORTWAVE SHEARING THROUGH THE MEAN PACIFIC RIDGE TOWARD THE NORTHWEST TUE REINFORCING THE BASE OF THE CENTRAL U.S. TROF BEFORE SHIFTING EAST INTO THE EASTERN THIRD OF THE U.S BY THURS EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE A HIGHLY ELONGATED TROUGH MOVING INTO THE NORTHWEST TODAY WILL REINFORCE THE BASE (AND WESTERN SIDE) OF THE LARGER SCALE TROUGH ACROSS THE SOUTHWEST...WITH THE TROUGH MOVING TOWARDS THE EAST COAST BY THURSDAY. THE TROUGH EVENTUALLY CATCHES UP TO THE DEPARTING COLD FRONT...WHICH SHOULD ALLOW FOR A SURFACE LOW REFLECTION TO DEVELOP ALONG THE FRONT OFF THE EAST COAST. MODELS ARE GENERALLY IN GOOD AGREEMENT WITH THIS SYSTEM. THE 12Z UKMET IS A BIT DEEPER/STRONGER WITH THE ENERGY INITIALLY AS IT DIVES SOUTHEAST REINFORCING THE TROUGH. IT THUS REMAINS DEEP AS THE SYSTEM MOVES INTO THE EAST COAST...BECOMING A NEGATIVELY TILTED WAVE BY 12Z FRIDAY IN THE MID ATLANTIC. THIS SOLUTION HAS LITTLE SUPPORT FROM THE OTHER DETERMINISTIC GUIDANCE AND IS ON THE EDGE OF THE ENSEMBLE ENVELOPE. SO WHILE NOT IMPOSSIBLE...IT SEEMS TO REPRESENT A MUCH LESS PROBABLE SOLUTION AT THIS TIME. THE 12Z ECMWF DOES SEEM A BIT SLOW WITH THE TROUGH APPROACHING THE EAST COAST LATER THURSDAY COMPARED TO THE GEM/NAM/GFS AND EVEN THE 12Z ECMWF MEAN. HOWEVER DIFFERENCES ARE RELATIVELY MINOR...AND THUS IT CAN BE INCLUDED IN THE OVERALL MODEL PREFERENCE. NEXT DEEPER TROF AND FRONT NEARING THE PACIFIC NORTHWEST COAST WED EVENING AND SETTLING ACROSS THE INTERMOUNTAIN WEST THURS EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z GFS AND 12Z ECMWF/GEM CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z UKMET HANDLES THE SHORTWAVE ENERGY DIFFERENTLY AS IT APPROACHES THE PACIFIC NORTHWEST. IT IS GENERALLY FURTHER NORTH WITH THE CORE OF THE ENERGY...AND QUICKER WITH THE FRONT. IT APPEARS TO LIE ON THE EDGE OR EVEN OUTSIDE OF THE ENSEMBLE SPREAD...AND THUS WILL CONTINUE LEANING AGAINST ITS SOLUTION. THE 0Z NAM IS NOW A BIT QUICKER THAN THE OTHER DETERMINISTIC GUIDANCE...AND SEEMS TO ALSO OFFER A LESS LIKELY SOLUTION. GOOD AGREEMENT SEEN WITH THE 0Z GFS AND 12Z ECMWF...AND THUS A BLEND OF THEIR SOLUTIONS SHOULD WORK WELL FOR THIS SYSTEM. EVEN THE 12Z GEM LOOKS PRETTY SIMILAR TO THESE SOLUTIONS...AND THUS COULD ALSO BE INCLUDED IN ANY BLEND FOR THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD