MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 202 AM EST FRI JAN 29 2016 VALID JAN 29/0000 UTC THRU FEB 01/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 0Z FINAL GUIDANCE EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SURFACE LOW TRACKING NORTH ACROSS THE WESTERN ATLANTIC FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE MOST OF THE IMPACTS FROM THIS SYSTEM REMAIN OFFSHORE...AND IN GENERAL MODELS ARE IN GOOD AGREEMENT. THE GFS AND GEFS MEAN REMAIN A BIT QUICKER THAN THE EITHER GUIDANCE...BUT DIFFERENCES ARE RELATIVELY MINOR AND A CONSENSUS TIMING IS PREFERRED. MID LEVEL SHORT WAVE CROSSING THE NORTH CENTRAL US FRI AND CROSSING GREAT LAKES SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 0Z GFS HAS COME MORE IN LINE WITH THE OTHER GUIDANCE IN HOW IT HANDLES THE SHORTWAVE ENERGY TRACKING EAST ACROSS THE GREAT LAKES AND OHIO VALLEY ON SATURDAY. NOT MUCH OF A SENSIBLE WEATHER IMPACT WITH THIS FEATURE AND THE GUIDANCE NOW APPEARS IN CLOSE ENOUGH AGREEMENT TO PREFER A GENERAL MODEL COMPROMISE SOLUTION. MID LEVEL SHORT WAVE REACHING THE PACIFIC NORTHWEST FRI AND CROSSING THE NORTHERN PLAINS INTO SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z ECMWF/GFS/NAM BLEND...WITH MORE WEIGHTING TOWARDS THE ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE BIGGER DIFFERENCES SEEN IN THE GUIDANCE WITH THIS SYSTEM...WITH DIFFERENCES HAVING A RATHER SIGNIFICANT IMPACT ON SENSIBLE WEATHER ACROSS PORTIONS OF THE MID/UPEPR MS VALLEY AND GREAT LAKES ON SUNDAY. MODELS ARE INITIALLY IN GOOD AGREEMENT ON SHORTWAVE ENERGY MOVING INTO THE PACIFIC NORTHWEST ON FRIDAY. THE GFS TRACKS MORE OF THIS ENERGY INTO THE CENTRAL PLAINS...AND EVENTUALLY SEES SOME PHASING BETWEEN SHORTWAVES...ALLOWING FOR A DEEPENING SYSTEM MOVING NORTHEAST TOWARDS THE GREAT LAKES ON SUNDAY. MEANWHILE THE ECMWF SHEARS MORE OF THE ENERGY OFF DIGGING IT MORE INTO THE DEVELOPING LONG WAVE TROUGH OVER THE SOUTHWEST. THIS RESULTS IN A MORE PROGRESSIVE/WEAKER AND FURTHER SOUTHEAST SYSTEM MOVING ACROSS THE GREAT LAKES AND OHIO VALLEY. THE NAM HAS TRENDED TOWARDS THE GFS...ALONG WITH THE SREF AND GEFS MEAN. MEANWHILE THE NON NCEP GUIDANCE (ECMWF/UKMET/GEM) ARE ALL IN THE MORE PROGRESSIVE AND SOUTHEAST CAMP...ALONG WITH MOST OF THE ECMWF ENSEMBLE MEMBERS. GIVEN THE SPREAD...RECENT CONSISTENCY AMONG THE MODELS STAYING IN TWO DISTINCT CAMPS...AND ENSEMBLE MEANS SUPPORTING THEIR DETERMINISTIC RUNS...THIS REMAINS A LOW CONFIDENCE FORECAST. TEND TO AGREE WITH THE PREVIOUS WPC PREFERENCE...IN THAT THE MORE PROGRESSIVE/SOUTHEAST SOLUTIONS ARE MORE LIKELY. HOWEVER WHILE THE NAM/GFS SOLUTIONS APPEAR LESS LIKELY...THEY CAN NOT BE COMPLETELY RULED OUT. THUS WILL PREFER A MODEL BLEND WEIGHTED AGAINST THE NCEP GUIDANCE. FINAL UPDATE: THE NEW 0Z ECMWF DID TREND A BIT MORE PHASED AND NEGATIVELY TILTED WITH THE SHORTWAVE CROSSING INTO THE GREAT LAKES ON SUNDAY...RESULTING IN A SLIGHTLY STRONGER AND NORTHWEST SURFACE LOW. THIS WAS A TREND TOWARDS THE GFS...ALTHOUGH THE GFS REMAINS MUCH DEEPER WITH THE LOW. THE PARALLEL GFS IS WEAKER AND MORE PROGRESSIVE WITH THE SYSTEM THAN THE DETERMINISTIC RUN...ADDING SOME CONFIDENCE THAT THE GFS IS LIKELY TOO DEVELOPED AND DEEP WITH THIS SYSTEM. THINK THE MOST LIKELY SOLUTION AT THIS TIME IS SOMEWHERE BETWEEN THE 0Z GFS/ECMWF/NAM...CLOSER TO A GFS TRACK WITH AN INTENSITY CLOSER TO THE ECMWF. THIS SOLUTION SEEMS TO FIT CURRENT TRENDS AND ENSEMBLE DATA BEST. STILL SLIGHTLY BELOW AVERAGE CONFIDENCE GIVEN THIS IS A PRETTY BIG MODEL SHIFT FROM SEVERAL CYCLES AGO...AND THE FACT THAT THE 0Z GEM/UKMET ARE HOLDING STEADY ON THE SOUTHEAST MORE PROGRESSIVE SOLUTION. LONG WAVE TROUGH APPROACHING THE WEST COAST LATE SAT DIGGING INTO SOUTHERN CA SUNDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 0Z ECMWF/GFS/UKMET CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS ARE BEGINNING TO COME MORE IN LINE WITH THIS SYSTEM AS MULTIPLE LOBES OF SHORTWAVE ENERGY MERGE RESULTING IN A DEEPENING TROUGH OVER THE SOUTHWESTERN PORTION OF THE COUNTRY SUNDAY INTO MONDAY. SHOULD ALSO SEE SURFACE LOW FORMATION ACROSS THE SOUTHWEST AS THIS ENERGY DIGS. THE 0Z NAM IS A SLOW/STRONG OUTLIER WITH THIS DEVELOPING LOW PRESSURE SYSTEM...WHICH IS OPPOSITE RECENT TRENDS...AND IS THUS CONSIDERED AN OUTLIER. THE 12Z GEM NOW LIES ON THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE...WHICH IS ALSO AGAINST RECENT TRENDS. THE 0Z GFS TRENDED A BIT QUICKER AND WEAKER WITH THE LOW IN THE 0Z TO 12Z MONDAY PERIOD...AND IS IN GOOD AGREEMENT WITH THE NEW OZ UKMET. THE 12Z ECMWF IS NOW A BIT OF AN OUTLIER BEING MORE SUPPRESSED...WEAKER AND SOUTHEAST WITH THE SYSTEM. HOWEVER IT HAS SUPPORT FROM MOST OF ITS ENSEMBLE MEMBERS...AND GIVEN THAT THE GFS/UKMET DID TREND SLIGHTLY TOWARDS IT...CAN NOT RULE IT OUT. THINK THE MOST LIKELY SOLUTION MAY END UP SOMEWHERE BETWEEN THE GFS/UKMET AND ECMWF SOLUTIONS. FINAL UPDATE: THE 12Z ECMWF TRENDED SLOWER AND MORE DEVELOPED WITH THE SURFACE LOW ACROSS THE SOUTHWEST FROM 0Z TO 12Z MONDAY. IT IS NOW MORE IN LINE WITH THE GFS/UKMET. THE GEM ALSO TRENDED IN THIS DIRECTION...BUT REMAINS A BIT FURTHER NORTH SIMILAR TO THE NAM. GIVEN RECENT TRENDS FEEL A CONSENSUS OF THE 0Z ECMWF/GFS/UKMET HANDLES THIS SYSTEM THE BEST AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD