Prognostic Meteorological Discussion
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FXUS10 KWNH 111647
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 AM EST THU FEB 11 2016

VALID FEB 11/1200 UTC THRU FEB 15/0000 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.


...ELONGATED SHORTWAVE LIFTING THROUGH THE NORTHEASTERN U.S.
TODAY...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: HIGH

BROAD CYCLONIC FLOW ANCHORS MUCH OF CENTRAL/EASTERN CANADA WITH AN
EMBEDDED SHORTWAVE CURRENTLY SPINNING ACROSS UPSTATE NY. MODELS
EXHIBIT GOOD AGREEMENT LIFTING THIS SYSTEM UP TOWARD NOVA SCOTIA
DURING THE NEXT 12 TO 24 HOURS WHICH WARRANTS A GENERAL MODEL
COMPROMISE.


...CLIPPER SYSTEM/DEVELOPING SURFACE LOW AFFECTING THE CAROLINAS
ON FRIDAY...

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

A CLIPPER SYSTEM SEEN ON WATER VAPOR IMAGERY MOVING THROUGH THE
NORTHERN HIGH PLAINS IS SPREADING LIGHT SNOW TO SECTIONS OF THE
DAKOTAS THIS MORNING. THIS FEATURE QUICKLY TRANSLATES
SOUTHEASTWARD REACHING THE SOUTHERN APPALACHIANS BY 12/1800Z.
ULTIMATELY THIS INDUCES AN AREA OF LOW PRESSURE OFF THE NC COAST
BY FRIDAY AFTERNOON. THERE ARE SUBTLE DIFFERENCES AMONG THE
SOLUTIONS WHICH HAS IMPACTS ON THE OUTER BANKS. CURRENTLY THE 12Z
NAM/09Z SREF MEAN ARE ON THE STRONGER/WESTERN SIDE OF THE SOLUTION
ENVELOPE WHILE THE 00Z UKMET REMAINS FLATTER/MORE SUPPRESSED. THE
BEST MIDDLE GROUND AT THIS POINT WOULD BE A BLEND OF THE 12Z
GFS/00Z ECMWF.


...COLD UPPER VORTEX SWEEPING THE NORTHEAST THIS WEEKEND...
...POLAR FRONT/SURFACE CYCLONE CROSSING ME...

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

A STRONG LOBE OF VORTICITY ACCOMPANIED BY SUB-492 DM HEIGHTS IS
CURRENTLY CENTERED OVER HUDSON BAY. MODELS AGREE ON ADVECTING THIS
SYSTEM SOUTHEASTWARD WITH ARCTIC AIR SURGING FROM THE GREAT LAKES
TO THE NORTHEASTERN U.S. FOR THIS WEEKEND. AS HAS BEEN THE CASE IN
RECENT DAYS...ECMWF ENSEMBLE MEMBERS HAVE FAVORED A MORE AMPLIFIED
PATTERN. THESE MEMBERS HAVE GRADUALLY RELAXED IN RECENT CYCLES
COMING CLOSER TO OTHER MODEL SOLUTIONS. THE 00Z ECMWF/ECMWF
ENSEMBLE ARE SLOWER TO ADVANCE THE UPPER VORTEX EASTWARD COMPARED
TO THE QUICKER 12Z GFS/06Z GEFS MEAN. WILL TAKE A SPLIT OF THESE
TWO CAMPS HERE.


...PROGRESSIVE SHORTWAVE PUSHING FROM THE PACIFIC NORTHWEST TO THE
GREAT LAKES...

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

UPPER RIDGING ACROSS THE WESTERN U.S. WILL BREAK DOWN IN RESPONSE
TO A PACIFIC SYSTEM WHICH WILL REACH THE WA BORDER BY EARLY
FRIDAY. THE 12Z NAM/00Z UKMET ARE QUICKER TO ADVANCE THE LEADING
EDGE OF HEIGHT FALLS THROUGH THE PACIFIC NORTHWEST ON FRIDAY.
TRAILING ENERGY SPILLS IN ITS WAKE LEADING TO A MORE ELONGATED
SYSTEM STRETCHING ACROSS THE NORTHWESTERN TIER. WHILE SLOWER WITH
THE INITIAL IMPULSE...THE OVERALL ADVANCE OF THE TROUGH ITSELF IS
SLOWER IN THE 12Z NAM. ENSEMBLE SPAGHETTIS SHOW SOME AMPLITUDE
SPREAD WITH MANY OF THE 00Z GEFS MEMBERS FAVORING MORE
AMPLIFICATION ACROSS THE CENTRAL PLAINS ON SUNDAY MORNING.
HOWEVER...THE ENSEMBLE MEAN ITSELF STAYS TO THE NORTH WHERE THE
BETTER CLUSTERING IS. THE OVERALL EVOLUTION OF THIS SYSTEM IS
COMPLICATED GIVEN THE NUMBER OF SHORTWAVES INVOLVED. THE BEST
ENSEMBLE SUPPORT NOTED IN RECENT SPAGHETTI DIAGRAMS IS FROM THE
00Z ECMWF ENSEMBLE MEAN. WPC FAVORS A BLEND OF THE 12Z GFS/00Z
ECMWF WITH INCLUSION OF THE 00Z ECMWF ENSEMBLE MEAN TO ACCOUNT FOR
GROWING UNCERTAINTIES.


...ADDITIONAL PACIFIC ENERGY SWINGING THROUGH THE NORTHERN ROCKIES
BY 15/0000Z...

PRELIMINARY PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

TRAILING IN THE WAKE OF THE LEAD SYSTEM WILL BE AN ELONGATED
IMPULSE WHICH TRACKS ALONG THE EASTERN EDGE OF A RENEWED UPPER
RIDGE ACROSS THE IMMEDIATE WEST COAST. THERE ARE A SLEW OF
SCENARIOS HERE BASED ON RECENT DETERMINISTIC GUIDANCE. THE 12Z GFS
TRACKS THE FEATURE THROUGH WESTERN WY WHILE THE 00Z ECMWF FAVORS
SOMETHING EASTWARD CLOSER TO THE HIGH PLAINS. AT THIS POINT THE
BEST PATH TO TAKE IS THE ENSEMBLE ROUTE FAVORING A BLEND OF THE
06Z GEFS/00Z ECMWF ENSEMBLE MEANS.


...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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