MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1232 PM EST SUN JAN 22 2017 VALID JAN 22/1200 UTC THRU JAN 26/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW ACROSS THE LOWER MS VALLEY SUN WITH ASSOCIATED STRONG SFC LOW LIFTING THROUGH THE MID-ATLANTIC MON...NEW ENGLAND ON TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE OVERALL MODELS REMAIN IN FAIRLY GOOD AGREEMENT SYNOPTICALLY WITH THIS SYSTEM...ALTHOUGH SOME WAFFLING WITH THE EXACT TIMING AND LOW POSITION CONTINUES. THE 0Z ECMWF AND 12Z NAM ARE A BIT CLOSER TO THE COAST THAN THE 12Z GFS...WITH THE 12Z UKMET A BIT SLOWER THAN THE CONSENSUS. HOWEVER ALL THE MODELS APPEAR TO BE WITHIN THE RANGE OF PLAUSIBLE OUTCOMES...AND THUS A GENERAL MODEL BLEND SHOULD HANDLE THE SYSTEM WELL FROM A SYNOPTIC STANDPOINT. BY WEDNESDAY THE 12Z NAM DOES BECOME AN OUTLIER WITH ITS TRACK WELL SOUTH OF NOVA SCOTIA...BUT BY THAT POINT SENSIBLE WEATHER IMPACTS ON THE US WILL BE DECREASING. LONGWAVE TROUGH OVER THE WEST COAST BY MON MORNING DOWNSTREAM SURFACE LOW INTO THE PLAINS FOR TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z UKMET AND 0Z ECMWF THROUGH TUESDAY...MORE TOWARDS THE 0Z ECMWF MEAN (OR A GFS/ECMWF COMPROMISE) BY TUESDAY NIGHT INTO WEDNESDAY CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS CONTINUE TO SUPPORT STRONG OVERALL AGREEMENT TO THE LONGWAVE TROUGH AS IT CROSSES INTO THE WESTERN US BY MONDAY NIGHT (24/00Z). AS THE LONGWAVE TROUGH REACHES THE INTERMOUNTAIN WEST...THIS SPURS LEE SURFACE CYCLOGENESIS AND THE FORMATION OF A CLOSED UPPER LOW CROSSING NEB. THE TWO BIGGEST OUTLIERS WITH THIS SYSTEM ARE THE 0Z GEM AND 12Z NAM. THE 12Z NAM IS TOO FLAT AND PROGRESSIVE WITH THE TROUGH/SHORTWAVE...RESULTING IN A WEAKER AND QUICKER LOW THAN THE MAJORITY OF THE MODELS/ENSEMBLES. ON THE OTHER HAND THE 0Z GEM IS MUCH SLOWER THAN THE CONSENSUS AND ALSO APPEARS UNLIKELY. THAT LEAVES THE 12Z GFS/UKMET AND 0Z ECMWF AS PLAUSIBLE MODEL OPTIONS. AGREE WITH THE OVERNIGHT SHIFT THAT LEANING TOWARDS THE 0Z ECMWF AND 12Z UKMET IS THE BETTER OPTION AT THIS TIME. THESE SOLUTIONS HAVE BEEN PRETTY CONSISTENT AND IN GOOD AGREEMENT WITH EACH OTHER. THE 06Z GEFS MEAN IS ALSO FURTHER SOUTH THAN THE DETERMINISTIC GFS AND CLOSER TO THE ECMWF/UKMET. THUS WHILE I WOULD NOT COMPLETELY DISREGARD THE 12Z GFS...WOULD LEAN MORE TOWARDS THE 12Z UKMET AND 0Z ECMWF. BY WEDNESDAY SPREAD IS EVEN BIGGER...WITH THE GFS MUCH QUICKER AND FURTHER NORTH THAN THE ECMWF/UKMET. BY THIS TIME GEFS/EC ENSEMBLE DATA SUGGESTS THAT GOING MORE IN BETWEEN THE GFS/ECMWF IS THE BETTER OPTION. IN FACT THE 0Z ECMWF MEAN IS PRETTY MUCH EXACTLY IN BETWEEN THE 0Z ECMWF AND 12Z GFS LOW POSITION AT 12Z WED. THUS WOULD LEAN CLOSER TO THE 0Z ECMWF MEAN BY LATER TUESDAY NIGHT INTO WEDNESDAY...WHICH IS PRETTY MUCH RIGHT IN BETWEEN THE 12Z GFS AND 0Z ECMWF SOLUTION. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD