Prognostic Meteorological Discussion
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FXUS10 KWNH 040448
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1248 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 NAM/GFS ALONG WITH PRELIMINARY
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...

PRELIMINARY PREFERENCE: MODEL COMPROMISE BETWEEN THE 00Z NAM/GFS
WITH THE 12Z ECMWF
FORECAST CONFIDENCE: SLIGHTLY 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. OUTSIDE OF THE GENERAL CONSENSUS ARE THE 12Z UKMET/CMC WITH
THE LATTER BEING MUCH SLOWER REGARDING THE OVERALL EVOLUTION. WILL
LEAN TOWARD THE STRONGER CONSENSUS FORMED BY THE 00Z NAM/GFS AND
12Z ECMWF.


...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...

PRELIMINARY PREFERENCE: THROUGH 06/1200Z...BLEND OF THE 00Z
GFS/12Z ECMWF...THEREAFTER: BLEND OF THE 18Z 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. EVENTUAL 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 18Z GEFS/12Z
ECMWF ENSEMBLE MEANS ARE OVER THE WESTERN ATLANTIC. THE PREFERENCE
WILL BE TO UTILIZE THE 00Z GFS/12Z ECMWF THROUGH DAY 2 BEFORE
SHIFTING TOWARD ENSEMBLE MEANS THEREAFTER.


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

PRELIMINARY PREFERENCE: THROUGH 06/1200Z...BLEND OF THE 00Z
GFS/12Z ECMWF...THEREAFTER: BLEND OF THE 18Z 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. ON THE WESTERN SIDE ARE THE
00Z NAM AND 12Z ECMWF/ECMWF ENSEMBLE MEAN WHILE OTHER SOLUTIONS
ARE SLIGHTLY OFF TO THE EAST. BY 06/1200Z...THE 00Z NAM BECOMES A
MORE WESTERN OUTLIER AS IT IS SLOWER TO EJECT THE SYSTEM EASTWARD
WHILE THE 12Z UKMET ENDS 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/12Z ECMWF COMBINATION LOOKS REASONABLE BEFORE MOVING TOWARD
THE AFOREMENTIONED MEANS.


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

PRELIMINARY 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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