Prognostic Meteorological Discussion
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FXUS10 KWNH 051644
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1143 AM EST FRI FEB 05 2016

VALID FEB 05/1200 UTC THRU FEB 09/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...AMPLIFIED TROUGH/STRONG COASTAL LOW LIFTING AWAY FROM NEW
ENGLAND THIS EVENING...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: HIGH

WATER VAPOR IMAGERY THIS MORNING INDICATED A WELL-DEFINED
SHORTWAVE CROSSING THE MID-ATLANTIC WITH AN ENHANCED MOISTURE
PLUME EXTENDING NORTHWARD FROM THE WESTERN CARIBBEAN. THIS
COMBINATION HAS FOCUSED MODERATE TO LOCALLY HEAVY SNOW OVER THE
EASTERN HALF OF NEW ENGLAND. OVERALL MODEL DIFFERENCES THE NEXT 12
TO 24 HOURS ARE MINIMAL SO A GENERAL MODEL COMPROMISE APPEARS
REASONABLE.


...SHORTWAVE STRENGTHENING OVER THE SOUTHERN/SOUTHEASTERN U.S.
EARLY SUNDAY...
...COASTAL LOW DEVELOPMENT OFFSHORE OF GA/SC...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
FORECAST CONFIDENCE: AVERAGE

A CONTINUED ACTIVE PATTERN WILL FEATURE ANOTHER AMPLIFYING SYSTEM
WHICH INITIALLY RESIDES OVER THE HIGH PLAINS REGION. MODELS DEPICT
A SPLIT FLOW REGIME IN PLACE WITH THE SOUTHERN STREAM DOMINATING
THE EVOLUTION. THE SPREAD WHICH WAS NOTED IN PREVIOUS DAYS HAS
DIMINISHED AS THE SLOWER ECMWF SUITE HAS NUDGED EASTWARD. MOST OF
THE UNCERTAINTY NOW RESIDES WITH THE EVOLUTION OF THE SURFACE
PATTERN OFF THE SOUTHEASTERN U.S. COAST. A PREPONDERANCE OF THE
GUIDANCE SHOW MORE THAN ONE SURFACE WAVE AT FIRST BEFORE EVOLVING
INTO ONE DOMINATE LOW WHICH ACCELERATES TOWARD THE WESTERN
ATLANTIC WATERS. ON SUNDAY MORNING...THE 12Z NAM PLACES MUCH
EMPHASIS ON THE MORE WESTERN WAVE WITH AN INTENSITY MUCH DEEPER
THAN ANY OTHER SOLUTION. WHILE NOT OUT OF THE REALM OF
POSSIBILITIES...ITS AGGRESSIVE NATURE IS SOMEWHAT QUESTIONABLE. BY
08/0000Z...MOST MODELS END UP IN THE BALLPARK TO ONE
ANOTHER...ALBEIT WITH DIFFERENT FORECAST EVOLUTIONS. THERE IS
PRETTY STRONG CLUSTERING WITH THE 12Z NAM/GFS AND 00Z ECMWF BUT
CANNOT INCLUDE THE 12Z NAM GIVEN THE EARLIER MENTIONED ISSUES. WPC
FAVORS A BLEND OF THE 12Z GFS/00Z ECMWF.


...NORTHERN STREAM AMPLIFICATION AFFECTING UPPER NEW ENGLAND BY
07/1200Z...

PRELIMINARY PREFERENCE: MODEL COMPROMISE BETWEEN THE 12Z GFS/00Z
ECMWF
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A BROAD REGION OF LOWER HEIGHTS CURRENTLY JUST WEST OF HUDSON BAY
WILL SINK SOUTHWARD BRINGING AN AXIS OF HEIGHT FALLS THROUGH
SOUTHEASTERN CANADA AND INTO UPPER NEW ENGLAND BY EARLY SUNDAY.
THE 00Z UKMET ENDS ON THE SLOWER END OF THE SPECTRUM WHILE THE 12Z
GFS REMAINS SLIGHTLY AHEAD OF ITS ENSEMBLE MEAN. HOWEVER...THIS
TREND STILL KEEPS THE 12Z GFS WITHIN THE LOW-END ENSEMBLE SPREAD.
WILL LEAN TOWARD A COMPROMISE OF THE 12Z GFS/00Z ECMWF SOLUTION
HERE.


...PROGRESSIVE PACIFIC SYSTEM REACHING THE NORTHWESTERN U.S. BY
06/0000Z...
...RESULTANT DEEP/MEAN TROUGH ANCHORING THE EASTERN HALF OF THE
CONUS...
...SURFACE PATTERN/ASSOCIATED AREAS OF LOW PRESSURE...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF WITH THE
00Z ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE: AVERAGE

PROGRESSIVE PACIFIC FLOW WILL CONTINUE WITH A SHORTWAVE REACHING
THE WA COAST BY 06/0000Z WITH THE 00Z CMC BEING A HAIR SLOWER
EARLY ON. AS THE SYSTEM ACCELERATES TOWARD THE NORTHERN
PLAINS...THE 12Z NAM BECOMES SLOWER/DEEPER ALTHOUGH ITS TIMING IS
ALONG THE LINES OF THE 00Z CMC/UKMET AND 09Z SREF MEAN.
MEANWHILE...THE 12Z GFS TRENDED A BIT QUICKER WHICH BRINGS IT
CLOSER TO THE 00Z ECMWF/ECMWF ENSEMBLE MEAN AND 06Z GFS-PARALLEL.
EVENTUALLY THE TROUGH BEGINS TO AMPLIFY LATE IN THE WEEKEND AS
HEIGHT FALLS DIG THROUGH THE UPPER GREAT LAKES. MODELS VARY WITH
THE RESULTANT SHAPE OF THE TROUGH AND SURFACE PATTERN BUT THE 12Z
GFS/06Z GFS-PARALLEL AND 00Z ECMWF ARE IN DECENT AGREEMENT WITH
THE ENSEMBLE MEANS. THIS WOULD SUGGEST AN INITIAL SURFACE LOW
MIGRATING THROUGH THE GREAT LAKES WITH SECONDARY DEVELOPMENT
LIKELY IN THE VICINITY OF THE CENTRAL APPALACHIANS/LOWER
MID-ATLANTIC. PLAN ON INCORPORATING THE 12Z GFS/00Z ECMWF WITH
INCLUSION OF THE 00Z ECMWF ENSEMBLE MEAN GIVEN THE UNCERTAINTIES
AT HAND.


...BROAD AXIS OF VORTICITY CIRCULATING IN THE VICINITY OF THE GULF
OF CA/SEA OF CORTEZ...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

UNDERNEATH A STRONG UPPER RIDGE ANCHORING THE WESTERN U.S...MODELS
DEPICT A BROAD WEAKNESS EXTENDING ACROSS THE SUBTROPICAL EASTERN
PACIFIC. THE GUIDANCE VARY WITH THE PLACEMENT OF THE VARIOUS
SHEARING VORTICITY CENTERS...BUT AS A WHOLE GENERAL AGREEMENT
EXISTS. A GENERAL MODEL COMPROMISE WOULD BE THE BEST OPTION IN
THIS CASE.



...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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