Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS10 KWNH 051655
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 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/06Z GEFS MEAN 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 AND THE 09Z SREF MEAN/06Z GEFS MEAN.  THE
00Z ECMWF WAS STRONGER WITH THE 700 MB LOW IN WY DAY 3...AND LEE
SIDE LOW LEVEL PRESSURE IN THE HIGH PLAINS.  THE 00Z ECMWF
ENSEMBLE MEAN WAS A BIT WEAKER AND FURTHER SOUTH...CLUSTERING
BETTER WITH THE GFS/SREF MEAN/GEFS MEAN.


...LOW MOVING EAST OF NEW ENGLAND TONIGHT TO NOVA SCOTIA AND
BEYOND FRI....

PREFERENCE: ECMWF/NAM/CANADIAN GLOBAL CONSENSUS
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/00Z 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/06Z 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
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 06Z 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 09Z SREF MEAN/06Z GEFS MEAN/12Z GFS/12Z
NAM
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODES/ENSEMBLE MEANS SHOW AN UPPER LEVEL TROUGH FORM 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.  AT TIMES THE OPERATIONAL ECMWF IS HIGHER AMPLITUDE THAN
OTHER MODELS WITH ITS ENSEMBLE MEAN NOT QUITE AS AMPLIFIED AS THE
OPERATIONAL RUN AND IN GOOD AGREEMENT WITH THE GFS.  THE 00Z
CANADIAN GLOBAL WAS A FEW HOURS FASTER THAN THE OTHER
MODELS/ENSEMBLE MEANS.
THE CANADIAN ENSEMBLE MEAN IS BOTH SLOWER AND LESS AMPLIFIED THAN
THE OPERATIONAL 00Z CANADIAN GLOBAL. WITH THE CANADIAN ENSEMBLE
MEAN TIMING WISE IN BETTER AGREEMENT WITH THE OTHER
MODELS/MEANS...I WOULD RECOMMEND PLACING LESS WEIGHT ON THE
OPERATIONAL CANADIAN GLOBAL TIMING. THE 09Z SREF MEAN AND 06Z GEFS
MEAN CLUSTER WELL WITH THE OPERATIONAL NAM/GFS SO A CONSENSUS OF
THESE SOLUTIONS IS PREFERRED.

...FRONT CROSSING THE UPPER MS VALLEY FRI/GREAT LAKES TO NEW YORK
AND MID ATLANTIC SATURDAY/NEW ENGLAND SUNDAY...

PREFERENCE: MULTI-MODEL CONSENSUS/06Z 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...AS 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.

...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.