Prognostic Meteorological Discussion
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FXUS10 KWNH 060645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST SAT FEB 06 2016

VALID FEB 06/0000 UTC THRU FEB 09/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SHORTWAVE STRENGTHENING OVER THE SOUTHERN/SOUTHEASTERN U.S. EARLY
SUNDAY
COASTAL LOW DEVELOPMENT OFFSHORE OF GA/SC SUN MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z UKMET/ECMWF BLEND
CONFIDENCE: AVERAGE

SPLIT FLOW REGIME IN PLACE ACROSS THE CONTINENT WITH A STRONGER
SOUTHERN STREAM CYCLONE CUTTING OFF ACROSS N TX ATTM WITH GENERAL
POSITIVE TILT TO THE LARGER SCALE WAVE OVERALL.  AS THE CYCLONE
PROGRESSES EAST THE TILT SHIFTS TOWARD NEUTRAL TO NEGATIVE AS IT
LIFTS UP THE EASTERN SEABOARD BY MONDAY.  ENSEMBLE SPREAD HAS BEEN
REDUCING WITH THE GEFS/CMCE MEMBERS SLOWING A BIT TOWARD THE ECENS
FOR BETTER OVERALL AGREEMENT IN TIMING/PLACEMENT OF THE
CUT-OFF...HOWEVER ENSEMBLE KEEP VACILLATING BETWEEN STRONGER OR
WEAKER CUT-OFFS.  THE 12Z CMC IS GENERALLY THE WEAKEST WHILE THE
NEW 00Z NAM IS STRONGEST...BOTH HOWEVER ARE ON THE COASTAL SIDE OF
THE ENSEMBLE SURFACE LOW CLUSTER WITH THE NAM MUCH STRONGER AND
SOUTH WHILE THE CMC IS THE FURTHEST NORTH OF THE OPERATIONAL
MODELS.  THE 12Z ECMWF IS ALSO ON THE STRONGER/CONSOLIDATED SIDE
LIKE THE NAM WHEN ROUNDING OUT OF FLORIDA.  THE 12Z UKMET TYPICAL
OF ITS BIAS IS ON LINE WITH THE CENTRAL PACKING OF THE
GUIDANCE/TRACK BUT IS ABOUT 3-6 HRS FASTER THAN MUCH OF THE
ENSEMBLE SUITE.   THE 00Z GFS IS GENERALLY WEAKER THAN 12Z ECMWF
AND THEREFORE LEADING THE ECMWF A BIT PARTICULARLY AS THE WAVE
WEAKENS/SHEARS OUT ACROSS THE NORTH ATLANTIC NEARING NOVA SCOTIA
BY MONDAY EVENING; STILL BOTH ECMWF/GFS ARE BOTH QUITE CENTRAL TO
THE ENSEMBLE PACKING AND REPRESENT THE 12Z ECENS MEAN/18Z GEFS
MEAN...TO PROVIDE CONFIDENCE IN BLENDING THE TWO.  AS SUCH A 00Z
GFS/12Z ECMWF BLEND IS PREFERRED AT AVERAGE CONFIDENCE.

07Z UPDATE:  THE ECMWF CONTINUED WITH THE OSCILLATION TOWARD A
WEAKER SOLUTION AGAIN...SHIFTING THE LOW A BIT SOUTHEAST WITH ITS
TRACK COMPARED TO THE 12Z RUN...WHICH SHIFTS IT FURTHER FROM THE
00Z NAM AS WELL AS EAST OF THE FAVORED 12Z ECENS MEAN. THE 00Z
UKMET SLOWED A BIT BUT REMAINS A ON THE STRONGER SIDE OF THE
GUIDANCE BUT MATCHES QUITE CLOSELY TO THE 00Z ECMWF. THE 00Z GEFS
REMAINS SLOWER AND CLOSER TO THE 12Z ECENS MEAN AND NEW UKMET. THE
00Z CMC REMAINS CONSISTENT WITH ITS 12Z RUN WITH SMALL DETAIL
DIFFERENCES ON THE WESTERN SIDE OF THE BEST CLUSTER PACKING.   ALL
THIS POINTS AWAY FROM INCLUSION OF THE 00Z GFS INTO A BETTER
AGREEMENT TOWARD THE ENSEMBLE MEANS... AS SUCH WILL NOW FAVOR A
00Z UKMET/ECMWF BLEND TO BEST REPRESENT THE GEFS/ECENS MEAN.
CONFIDENCE IS A BIT BETTER IN CLOSER AGREEMENT WITHIN THIS BLEND
BUT LARGE SPREAD REMAINS...FOR ONLY AVERAGE CONFIDENCE OVERALL.


NORTHERN STREAM AMPLIFICATION AFFECTING UPPER NEW ENGLAND BY
SUNDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

A LOBE OF THE ARCTIC CYCLONE IS TRACKING ALONG THE SW COAST OF
HUDSON BAY AND WILL DIP INTO CENTRAL/SOUTHERN QUEBEC BY SUNDAY
MORNING CLIPPING NORTHERN NEW ENGLAND.  MODELS HAVE BEEN GETTING A
BETTER HANDLE IN TIMING/PLACEMENT OF THE WAVE INCLUDING AS IT
SHEARS OUT ACROSS THE ST. LAWRENCE SEAWAY TOWARD
NEWFOUNDLAND...ALL EXCEPT THE UKMET WHICH REMAINS
UNCHARACTERISTICALLY SLOW.  THE 00Z NAM IS ALSO A SHADE SLOW BUT
NO LONGER SIGNIFICANTLY ENOUGH TO INCLUDE IT INTO THE PREFERRED
BLEND.  AS SUCH WILL SUPPORT A NON-UKMET BLEND AT ABOVE AVERAGE
CONFIDENCE GIVEN THE BETTER RUN TO RUN CONSISTENCY FOR THE WAVE
EVOLUTION.

07Z UPDATE: THE 00Z UKMET HAS PICKED UP PACE TO BECOME IN
AGREEMENT WITH THE REST OF THE 00Z MODEL GUIDANCE TO SUPPORT AN
OPERATIONAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE.


PACIFIC SYSTEM CURRENTLY NEAR VANCOUVER ISLAND SHIFTS ACROSS THE
US/CANADA BOARDER EVENTUALLY DEEPENING INTO A LARGE SCALE MEAN
CYCLONE THE EASTERN HALF OF THE CONUS BY TUESDAY WITH ASSOCIATED
STRONG SURFACE REFLECTION MOVING THROUGH THE GREAT LAKES AND
COASTAL CYCLOGENESIS TUESDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS/ECMWF THROUGH 09/00Z
            00Z NAM/ECMWF
CONFIDENCE: AVERAGE BEFORE 09/00Z...SLIGHTLY BELOW AFTER

A STRONG WAVE CAN BE SEEN ENTERING THE PACIFIC NORTHWEST NEAR
VANCOUVER ISLAND ON WV.  MODELS TRANSLATE THIS WAVE ACROSS THE
US/CANADA BOARDER WRAPPING UP INTO THE CENTROID OF THE DEVELOPING
LARGER SCALE CYCLONE NEAR THE BOUNDARY WATERS OF N MN BEFORE THE
TRAILING ENERGY OF THE WAVE BEGINS TO CARVE OUT THE WESTERN SIDE
OF THE LARGER SCALE CYCLONE ACROSS THE NORTHERN/CENTRAL GREAT
PLAINS SUNDAY AFTERNOON INTO EVENING.  BY THIS TIME THE 12Z
UKMET/CMC ARE LESS CONSOLIDATED WITH THE INNER CORE OF THE LOW IN
MN UNLIKE THE 00Z NAM/GFS AND 12Z ECMWF.  THE LATTER HAVE ALSO
BEEN TRENDING CLOSER TOGETHER FROM RUN TO RUN AS SEEN IN THE 12Z
ENSEMBLE SPREAD AS WELL WITH VERY TIGHT SURFACE LOW
CLUSTERING...WITH THE OPERATIONAL RUNS REPRESENTING THE MIDDLE
QUITE WELL THROUGH 08/00Z.  AS THE CYCLONE EXPANDS IN BREADTH AND
COVERAGE BY MONDAY EVENING...MODELS ARE IN FAIRLY GOOD AGREEMENT
BUT THE INTERNAL FEATURES AND WAVES RESULT IN SIGNIFICANT
TIMING/WAVE INTERACTIONS DIFFERENCES THAT RESULT IN DIFFERENCES IN
PLACEMENT TIMING OF SENSIBLE WEATHER/QPF (PLEASE REFER TO QPFPFD
FOR ADDITIONAL DETAILS).  THE SPREAD OF THE INNER DETAILS BECOMES
LARGE BY DAY 3 AND AS SUCH WILL FAVOR TOWARD THE ENSEMBLE MEANS TO
WASH OUT SOME OF THIS VARIABILITY THAT WILL OBVIOUSLY CHANGE RUN
TO RUN.

THE 00Z NAM DIGS THE TROF BY TUESDAY BUT IS ALSO A BIT STRONGER
INTO THE BASE OF THE TROF RESULTING IN A DEEPER NEGATIVE
TILT/NARROWER ELONGATION OF THE OVERALL TROF FROM NW TO SE THAN
THE BULK OF ENSEMBLE MEMBERS.  THE 12Z ECMWF IS A BIT WEAKER/LESS
CONSOLIDATED ACROSS WITH THE INNER CORE OF THE CYCLONE.  WHILE THE
00Z GFS BECOMES A BIT FASTER WITH THE LEADING WAVE OF THE CYCLONE
ACROSS THE SOUTH AND ROUNDING INTO THE CAROLINAS BY TUESDAY
MORNING...RESULTING IN A STRONGER AND FURTHER NORTHEAST SURFACE
REFLECTION...DRIVEN BY THE DOWNSTREAM FASTER EXIT/SHEARING OF THE
WAVE DESCRIBED IN THE SECTION ABOVE...MAKING IT LESS LIKELY.  IN
THIS COASTAL CYCLOGENESIS THE GFS IS FASTER THAN THE GEFS WHILE
THE ECMWF IS SLOWER THAN ITS ECENS MEAN...WHICH WOULD FAVOR
SHIFTING TOWARD THE MEANS THE LATER IN THE FORECAST PERIOD ONE
GOES WITH THE BLEND.

STILL THE SREF/GEFS/ECENS MEANS ARE IN FAIRLY STRONG AGREEMENT BUT
USE OF THE 00Z GFS/12Z ECMWF TO REPRESENT THEM IN A BLEND SEEMS
FAIR UNTIL DAY 3...WHEN THE MEANS (21Z SREF/18Z GEFS/12Z ECENS)
ARE BETTER GIVEN ISSUES DESCRIBED ABOVE WITH THE 00Z GFS IN
PARTICULAR. CONFIDENCE IN THE LARGE SCALE IS FAIRLY HIGH BUT AS
STATED BEFORE INTERNAL DETAILS IS VERY LOW... AS SUCH THE
CONFIDENCE IS AVERAGE OVERALL.

07Z UPDATE: THERE IS LITTLE CHANGE IN THE LARGE SCALE EVOLUTION
WITH RESPECT TO THE 00Z UKMET/CMC AND ECMWF... INTERNAL
DIFFERENCES HOWEVER ARE STARKLY DIFFERENT.  THE 00Z ECMWF`S INNER
CORE CONSISTS OF TWO LOBES OF VORTICITY THAT INCREASE ROTATIONAL
DISTANCE...THIS HELPS TO ELONGATE THE OVERALL TROF AS WELL BUT
ALSO BE A BIT SLOWER MORE IN LINE WITH THE 00Z NAM THAN THE 00Z
GFS.  THIS IS MOST DRAMATIC OVERALL BY DAY 3; AS STATED PRIOR
THESE INTERNAL DIFFERENCES WILL CONTINUE VARY GREATLY...SO WHEN IT
IS THE GREATEST (DAY 3 PLUS) WILL CONTINUE TO FAVOR THE
MEANS...WHICH CAN BE BEST REPRESENTED BY THE 00Z GFS/ECMWF/NAM UP
TO 09/00Z BUT CLOSER TO THE 00Z ECMWF/NAM BLEND AFTER TO BEST
REPRESENT THE SREF/ECENS/GEFS MEAN. CONFIDENCE IS HIGHER
EARLY...BUT REDUCE TO SLIGHTLY BELOW AVERAGE WITH THE
TIMING/DEVELOPMENT OF THE COASTAL LOW ON TUESDAY.


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

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

GALLINA

$$




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