Prognostic Meteorological Discussion
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000
FXUS10 KWNH 040639
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 AM EDT WED MAY 04 2016

VALID MAY 04/0000 UTC THRU MAY 07/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...PROGRESSIVE SHORTWAVE CROSSING THE CENTRAL GULF COAST BY
04/1800Z...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

ALONG THE SOUTHERN EXTENT OF A BROAD LONGWAVE TROUGH EXTENDING
OVER THE EASTERN HALF OF THE CONUS...A PROGRESSIVE SHORTWAVE WILL
MIGRATE FROM THE RED RIVER VALLEY TOWARD THE CENTRAL/EASTERN GULF
COAST. THE 00Z UKMET/CMC HAVE EACH MADE ADJUSTMENTS TO THEIR
FORECASTS TO BRING THEIR SOLUTIONS CLOSER TO THE PACK. WITH THAT
SAID...WILL SHIFT THE PREFERENCE TO A GENERAL MODEL COMPROMISE
HERE.


...INITIAL HEIGHT FALLS TRACKING ACROSS THE GREAT LAKES...
...BROAD UPPER LOW AFFECTING THE EASTERN SEABOARD FOR THE
REMAINDER OF THE PERIOD...
...SERIES OF SURFACE WAVES OVER THE WESTERN ATLANTIC...

FINAL PREFERENCE: THROUGH 06/1200Z...BLEND OF THE 00Z
GFS/ECMWF...THEREAFTER: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: AVERAGE...THEN BECOMING SLIGHTLY BELOW AVERAGE

AHEAD OF A SHORTWAVE ADVANCING THROUGH THE GREAT LAKES...MODERATE
SHOWERS HAVE BROKEN OUT ALONG THE COLD FRONT EXTENDING ACROSS THE
UPPER GREAT LAKES REGION. EVENTUALLY THIS SYNOPTIC SYSTEM WILL
EVOLVE INTO AN UPPER LOW WHICH SHOULD BECOME A MAINSTAY FEATURE
FOR THE REMAINDER OF THE SHORT RANGE PERIOD. BY THURSDAY
MORNING...THE 00Z NAM IS ON THE SOUTHERN END OF THE SPREAD
FAVORING A CLOSED LOW OVER THE SOUTHERN APPALACHIANS. THIS FEATURE
WILL GRADUALLY SHIFT NORTH AND EAST WITH A POSITION IN THE
VICINITY OF THE VA CAPES AND NC OUTER BANKS BY THE FOLLOWING
MORNING. THERE HAS BEEN A GENERAL SLOWING TREND IN THE GUIDANCE
COMPARING THE PAST FEW SPAGHETTI PLOTS IN RECENT MODEL CYCLES WITH
THE GEFS/ECMWF ENSEMBLE MEMBERS WELL CLUSTERED. THERE ARE
CONSIDERABLE DIFFERENCES AT THE SURFACE ON DAY 3 WHICH LEADS TO
PLENTY OF QPF UNCERTAINTIES. FOR INSTANCE...BY 07/0000Z...THE 00Z
GFS STILL HAS A LOW OVER THE CHESAPEAKE BAY WHILE THE ENSEMBLE
MEANS ARE GENERALLY OVER THE WESTERN ATLANTIC. THE PREFERENCE WILL
BE TO UTILIZE THE 00Z GFS/ECMWF THROUGH DAY 2 BEFORE SHIFTING
TOWARD ENSEMBLE MEANS THEREAFTER.


...UPPER TROUGH CLOSING OFF IN THE VICINITY OF SOUTHERN CA...

FINAL PREFERENCE: THROUGH 06/1200Z...BLEND OF THE 00Z
GFS/ECMWF...THEREAFTER: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: AVERAGE...THEN BECOMING SLIGHTLY BELOW AVERAGE

AN UPPER TROUGH MOVING TOWARD THE SOUTHERN CA COAST IS EXPECTED TO
CUT OFF LEADING TO A PRONOUNCED OMEGA BLOCK SETUP ACROSS NORTH
AMERICA. REGARDING THE POSITION OF THE CLOSED LOW...THERE ARE SOME
DIFFERENCES BY AS EARLY AS 05/1200Z. MANY OF THE 00Z SOLUTIONS
HAVE JOINED THE POSITION SUPPORTED BY THE 00Z NAM/12Z ECMWF WHICH
IS WEST OF THE QUICKER 00Z GFS/GEFS MEAN. BY 06/1200Z...THE 00Z
NAM BECOMES A MORE WESTERN OUTLIER AS IT IS SLOWER TO EJECT THE
SYSTEM EASTWARD WHILE THE 00Z/12Z UKMET END UP ON THE MORE
PROGRESSIVE SIDE. WHILE OTHER MODELS SOMEWHAT CLUSTER OVER THE
SOUTHWESTERN U.S...THERE ARE PLENTY OF SMALLER-SCALE DIFFERENCES
REVOLVING AROUND THE ROTATING SHORTWAVES. THROUGH DAY 2...FEEL
DETERMINISTIC SOLUTIONS CAN BE RELIED ON BEFORE GOING TOWARD THE
ENSEMBLE MEANS FOR DAY 3 WHICH FOLLOWS SUIT WITH THE EASTERN U.S.
CLOSED LOW. THE 00Z GFS/ECMWF COMBINATION LOOKS REASONABLE BEFORE
MOVING TOWARD THE AFOREMENTIONED MEANS.


...COLD FRONT SWEEPING THROUGH THE NORTHERN TIER STATES BY EARLY
SATURDAY...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

AMPLIFIED FLOW IN THE NORTHERN STREAM WILL DRAG A COLD FRONT
THROUGH THE NORTHERN PLAINS/UPPER MIDWEST BY EARLY IN THE WEEKEND.
OVERALL DIFFERENCES ARE NOT TOO SUBSTANTIAL AT THIS POINT SO A
GENERAL MODEL COMPROMISE IS RECOMMENDED.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

RUBIN-OSTER

$$




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