MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 219 AM EST SAT JAN 30 2016 VALID JAN 30/0000 UTC THRU FEB 02/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 0Z MODEL EVALUATION INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ MID-LEVEL SHORTWAVE MOVING TOWARDS THE NORTHERN PLAINS TODAY DEVELOPING SURFACE LOW MOVING FROM THE CENTRAL PLAINS INTO THE GREAT LAKES REGION SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z GFS BLENDED WITH THE 12Z ECMWF/UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE GUIDANCE FINALLY COMING INTO BETTER AGREEMENT WITH THIS SYSTEM AS IT MOVES INTO THE GREAT LAKES. THE GFS CONTINUES TO TREND WEAKER AND MORE PROGRESSIVE WITH THIS SYSTEM...WITH THE NEW 0Z RUN COMING INTO PRETTY GOOD AGREEMENT WITH THE ECMWF AND UKMET FROM 12Z. THUS WOULD APPEAR THAT A SOLUTION BETWEEN THE PREVIOUSLY STRONG GFS AND WEAK ECMWF HAS A GOOD CHANCE OF VERIFYING. THE 0Z NAM HAS TRENDED WEAKER AND SOUTHEAST...HOWEVER IT STILL REMAINS ON THE STRONGER/NORTHWEST SIDE OF THE GUIDANCE ENVELOPE...ALONG WITH THE 12Z GEM. THUS THE WPC PREFERENCE WILL BE A BLEND OF THE 0Z GFS AND 12Z ECMWF/UKMET. THIS PREFERENCE CONTINUES AS THE LOW TRACKS INTO SOUTHEAST CANADA DRAGGING A FRONT ACROSS THE EAST COAST. THE ECMWF/UKMET ARE A BIT STRONGER WITH SUBTLE SHORTWAVE ENERGY THAT INTERACTS WITH THE FRONT ON MONDAY ALLOWING FOR A WEAK SURFACE REFLECTION TO DEVELOP ACROSS VA RESULTING IN AN INCREASED QPF THREAT. WOULD APPEAR THE GFS IS BEGINNING TO TREND A BIT TOWARDS THE ECMWF/UKMET WITH THIS SYSTEM...AND FEEL A SOLUTION CLOSER TO THE ECMWF/UKMET IS MOST LIKELY AT THIS TIME. LONGWAVE TROUGH MOVING THROUGH THE SOUTHWEST U.S. SUNDAY INTO EARLY NEXT WEEK SURFACE LOW TRACKING THROUGH THE SOUTHWEST INTO THE THE SOUTHERN PLAINS MONDAY EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z GFS AND 12Z ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS REMAIN IN PRETTY GOOD AGREEMENT WITH THE DEEPENING LONGWAVE TROUGH...THE RESULTANT SURFACE LOW FORMATION ACROSS THE SOUTHWEST ON SUNDAY...AND WITH THE TIMING/TRACK OF THE LOW INTO THE SOUTHERN/CENTRAL PLAINS ON MONDAY. WHILE THE OVERALL PATTERN SEEMS PRETTY LOCKED IN AND THE CONFIDENCE IS HIGH ON A SIGNIFICANT SYSTEM...WILL LIKELY CONTINUE TO SEE SUBTLE SHIFTS NORTH/SOUTH AND SLOW/FAST IN THE GUIDANCE OVER THE COMING DAYS...RESULTING IN A LOWER CONFIDENCE IN THE DETAILS OF THE SYSTEM. THE 12Z ECMWF/UKMET ARE CLUSTERED VERY WELL WITH THE TIMING/LOCATION OF THE LOW AS IT MOVES ACROSS THE PLAINS. THE NEW 0Z GFS DID INDEED TREND A BIT QUICKER TO BETTER MATCH THE ECMWF/UKMET. HOWEVER IT ALSO TRENDED A TAD NORTH OF THE ECMWF/UKMET...WITH THE 18Z GFS ACTUALLY BEING IN CLOSER AGREEMENT ON THE NORTHWARD EXTENT OF THE SYSTEM. WHILE THIS NORTHWARD SHIFT DOES HAVE A BIG IMPACT ON QPF/SNOW AMOUNTS FOR A NARROW REGION...IT IS A RELATIVELY MINOR SHIFT IN THE LARGE SCHEME OF THINGS AND CERTAINLY WITHIN THE RANGE OF POSSIBILITIES. THUS FOR NOW THE WPC PREFERRED BLEND IS A BLEND OF THE 0Z GFS AND 12Z ECMWF/UKMET. THE 0Z NAM AND 12Z GEM ARE THE TWO SETS OF GUIDANCE THAT APPEAR TO BE ENOUGH OF AN OUTLIER TO BE CONSIDERED UNLIKELY SOLUTIONS AT THIS TIME. BOTH ARE SLOWER AND FURTHER SOUTH WITH THE SYSTEM...WHICH IS AGAINST RECENT RATHER CONSISTENT TRENDS IN THE OTHER GLOBAL GUIDANCE SETS. ALSO THE FACT THAT THE NAM/GEM TYPICALLY ARE TWO OF THE LESS SKILLFUL MODELS BY DAY 3 IS ANOTHER REASON TO LEAN AGAINST THEIR OUTLIER SOLUTIONS. ONE THING OF CONCERN IS THAT THE GEFS MEAN AND ECMWF MEAN ACTUALLY ARE A BIT CLOSER TO THE MORE SUPPRESSED NAM/GEM SOLUTIONS. HOWEVER THERE IS VERY GOOD AGREEMENT AMONG THE DETERMINISTIC GUIDANCE FOR A STRONG DYNAMIC SYSTEM...AND AT TIMES IN THESE SCENARIOS THE ENSEMBLE MEANS CAN FALSELY SHOW A MORE SUPPRESSED AND WEAKER SYSTEM. THUS FOR NOW WE ARE FINE WITH LEANING AGAINST THE ENSEMBLE MEANS AND CLOSER TO THE MORE CONSISTENT CLUSTER OF THE GFS/ECMWF/UKMET. HOWEVER WILL LEAVE OUR CONFIDENCE AT ONLY SLIGHTLY ABOVE AVERAGE GIVEN SOME LINGERING UNCERTAINTY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD