Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8
148 FXUS10 KWNH 051845 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 244 PM EDT THU MAY 05 2016 VALID MAY 05/1200 UTC THRU MAY 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING PREFERENCES/CONFIDENCE GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. ...SYSTEM MOVING INTO THE SOUTHWEST AND GREAT BASIN...CONTINUING INTO THE CENTRAL ROCKIES AND ADJACENT PLAINS THIS WEEKEND... PREFERENCE: GFS/UKMET/ECMWF CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 06Z-12Z NAM IS SLOW/LOWERS HEIGHTS FURTHER SOUTHWEST WITH THE 500 MB TROUGH THAN THE OTHER MODELS ACROSS AZ/ADJACENT NORTHWEST MEXICO WITH THIS SYSTEM ON SATURDAY NIGHT/SUNDAY MORNING. THE OTHER MODELS SHOW VERY GOOD AGREEMENT, SO PREFER A CONSENSUS OF THE CANADIAN/UKMET/GFS/12Z ECMWF AND THE 12Z GEFS MEAN. THE 12Z ECMWF TRENDED WEAKER WITH THE 700 MB LOW IN WY DAY 3...BRINGING IT INTO BETTER AGREEMENT WITH THE OTHER MODELS. THE 00Z ECMWF ENSEMBLE MEAN CLUSTERED WELL WITH THE SREF MEAN/GEFS MEAN. ...LOW MOVING EAST OF NEW ENGLAND TONIGHT TO NOVA SCOTIA AND BEYOND FRI.... PREFERENCE: 12Z ECMWF/NAM BLEND CONFIDENCE: AVERAGE THE 12Z GUIDANCE IS SHOWING A TREND TOWARDS CONVERGENCE OF SOLUTIONS, ALTHOUGH THE 12Z GFS/06Z GEFS MEAN ARE STILL EAST OF THE NAM/ECMWF/UKMET/09Z SREF MEAN/12Z CANADIAN GLOBAL LOW TRACK FORECASTS. A CONSENSUS APPROACH WOULD TAKE THE LOW WEST OF THE GFS/GEFS MEAN. THE 12Z UKMET MARKS THE SLOW EDGE OF THE GUIDANCE SUITE. THIS IS CONSIDERED A LOW PROBABILITY SOLUTION AS THE LOW IS EJECTING DOWNSTREAM FROM THE CLOSED LOW IN THE MID ATLANTIC AND NO BLOCK IS IN PLACE TO PREVENT STEADY FORWARD PROGRESSION. LOW DRIFTING NORTH ACROSS THE MID-ATLANTIC FRIDAY/SATURDAY PREFERENCE: 09Z SREF MEAN/12Z GEFS MEAN BLEND CONFIDENCE: AVERAGE THE MODELS PERSIST IN SHOWING TIMING/INTENSITY DIFFERENCES WITH THE LOW AS IT MOVES SLOWLY NORTH NEAR THE MID ATLANTIC COAST. THE 12Z ECMWF/UKMET ARE ON THE FAST SIDE OF THE GUIDANCE SUITE IN MOVING THE LOW NORTH THROUGH 00Z SAT. THE 00Z ECMWF ENSEMBLE MEAN SHOWS A PROGRESSION A FEW HOURS SLOWER THAN THE OPERATIONAL RUN...AND CLUSTERS WELL WITH THE 12Z GEFS MEAN/09Z SREF MEAN. DUE TO GOOD OVERLAP/CLUSTERING OF THESE SOLUTIONS... PREFER A COMPROMISE OF THOSE SOLUTIONS. THE 12Z GFS IS AT TIMES DEEPER WITH THE 700 MB CLOSED LOW AND SLOWER TO WEAKEN THE LOW THAN OTHER GUIDANCE...WITH THE MEAN CLOSER TO THE INTENSITY OF THE OTHER MODELS/ENSEMBLE MEANS. CONSEQUENTLY...LOW WEIGHTING SHOULD ALSO BE PLACED ON THE OPERATIONAL GFS/GFS PARALLEL AND MORE ON THE GFS ENSEMBLE MEAN. ...SYSTEM CROSSING THE PACIFIC NORTHWEST AND NORTHERN ROCKIES SATURDAY NIGHT...DRIFTING EAST ON TO THE NORTHERN HIGH PLAINS SUN... PREFERENCE: CONSENSUS OF 12Z GEFS MEAN/12Z GFS/12Z CANADIAN GLOBAL/UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS/ENSEMBLE MEANS SHOW AN UPPER LEVEL TROUGH MOVING FROM THE EASTERN PACIFIC MOVING ONSHORE SAT LATE AFTERNOON/EVENING AND CONTINUING INTO THE NORTHERN ROCKIES SAT NIGHT/EARLY SUN AND FURTHER EAST ON TO THE NORTHERN HIGH PLAINS SUNDAY. TYPICAL AMPLITUDE DIFFERENCES AND TIMING DIFFERENCES EXIST IN THE GUIDANCE SUITE. THE 12Z ECMWF HAS SHARPENED THE WAVE AMPLITUDE AND MOVED THE 500 MB TROUGH EAST FASTER... WHICH MAKES IT FASTER TO LOWER HEIGHTS IN THE NORTHERN ROCKIES AND HIGH PLAINS THAN THE OTHER MODELS. THE BIG DIFFERENCE SIN WITH THE TRACK OF THE CLOSED LOW IN WESTERN CANADA...WITH DIFFERENCES LOWER IN MAGNITUDE AND/OR TIMING IN THE US. THE ECMWF ENSEMBLE MEAN WAS NOT QUITE AS AMPLIFIED AS THE OPERATIONAL RUN AND IN BETTER AGREEMENT WITH THE GFS. THE 12Z CANADIAN GLOBAL NOW CLUSTERS BETTER TIMING WISE WITH THE OTHER MODELS/ENSEMBLE MEANS. THE 09Z SREF MEAN AND 12Z GEFS MEAN CLUSTER WELL WITH THE OPERATIONAL NAM/GFS SO A CONSENSUS OF THESE SOLUTIONS IS PREFERRED...ALONG WITH THE UKMET. ...FRONT CROSSING THE UPPER MS VALLEY FRI/GREAT LAKES TO NEW YORK AND MID ATLANTIC SATURDAY/NEW ENGLAND SUNDAY... PREFERENCE: MULTI-MODEL CONSENSUS/12Z GEFS MEAN CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT ON THE DEPICTION OF A COLD FRONT EMERGING FROM THE NORTHERN PLAINS THU NIGHT AND CROSSING THE UPPER MS VALLEY FRI AND THE GREAT LAKES FRI NIGHT-SAT. A WAVE OF LOW PRESSURE IS FCST TO DEVELOP ALONG THE FRONT BY THE MODELS OVER LAKE HURON AND SOUTHEAST ONTARIO FRI NIGHT AND MOVE INTO QUEBEC SAT/SUN. THE TRAILING FRONT CROSSES NY/MID ATLANTIC SAT NIGHT AND NEW ENGLAND SUN. MINOR TIMING/DIFFERENCES AMONG THE MODELS/ENSEMBLE MEANS ARE NOTED WITH A CONSENSUS APPROACH USED TO MITIGATE THESE DIFFERENCES. NO ONE FORECAST STANDS OUT AS AN OUTLIER THROUGH 12Z SUN...WITH THE 12Z NAM BECOMING THE SLOWER MOVING FORECAST WITH LOW PRESSURE IN QUEBEC. THE 12Z UKMET CHANGED CONTINUITY AND ASSERTIVELY LOWERS HEIGHTS IN NEW ENGLAND MORE THAN OTHER MODELS SUN SO IS CONSIDERED TO BE A LOW PROBABILITY SOLUTION. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... PETERSEN $$

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.