Prognostic Meteorological Discussion
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912
FXUS10 KWNH 080428
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 PM EST SUN FEB 07 2016

VALID FEB 08/0000 UTC THRU FEB 11/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CLOSED LOW STRENGTHENING OFF THE SOUTHEASTERN U.S. COAST
SURFACE CYCLONE DEEPENING ALONG THE GULF STREAM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OPERATIONAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

VERY STRONG OCCLUDED LOW IS NOW WELL DEVELOPED OFF THE CAROLINA
COASTLINE DRIFTING EAST...SOME SMALL DISPLACEMENT ERRORS WERE
NOTED INITIALLY WITH THE 12Z UKMET BUT STABILIZED AS IT DRIFTS
NORTH-NORTHEAST TOWARD THE NE TIP OF NOVA SCOTIA BY 09/12Z TUE...
UNDER FAIRLY STRONG AGREEMENT BOTH AT THE SURFACE/ALOFT...WITH THE
00Z NAM/12Z CMC LAGGING EVER SO SLIGHTLY.  IT IS AFTER THIS POINT
INFLUENCES FROM UPSTREAM DEEPENING CYCLONE WILL HELP TO SHEAR THE
SYSTEM VERTICALLY DRAWING THE UPPER LEVELS WEST AND LOW LEVELS
SLOWLY TOWARD NEWFOUNDLAND.  THE CMC IS DRAWN WEST ALOFT A BIT
MORE AND 12Z UKMET LEAST...AT THE SURFACE THE 00Z GFS IS FURTHEST
EAST THOUGH THE 18Z GEFS MEAN IS FURTHER EAST.  OVERALL THE
DIFFERENCE APPEAR MINOR SPECIFICALLY WITH THIS SYSTEM TO SUPPORT
AN OPERATIONAL MODEL BLEND BUT WITH SOME INCREASING SPREAD AND
INFLUENCES TUES..WILL WEIGHT HEAVIER TO MORE STABLE/INTERNALLY
CONSISTENT MODELS OF THE 00Z GFS/12Z ECMWF AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.


BROAD SHORTWAVE DIGGING THROUGH THE UPPER MIDWEST THIS MORNING
EVENTUAL CLOSED LOW MIGRATING FROM THE UPPER GREAT LAKES TO THE OH
VALLEY
PAIR OF SURFACE CYCLONES AFFECTING THE GREAT LAKES AND VA COASTAL
LOW AND LINGERING WAKE LOW PRESSURE/SURFACE LOWS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS AND 12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE BROAD BUT EXPANDING UPPER TROF IS STARTING TO SETTLE ACROSS
THE GREAT LAKES WITH FAIRLY GOOD MODEL AGREEMENT IN THE INTERNAL
CENTER OF THE WAVE AS A WHOLE INCLUDING THE WEAKENING SURFACE
REFLECTION.  STILL SUBTLE TIMING DIFFERENCE WITH INTERNAL WAVES
CONTINUES TO PLAGUE MESOSCALE BUT IMPORTANT IMPACT DETAILS...BUT
THIS IS EVEN TRENDING BETTER AS THE 00Z GFS WHICH HAD BEEN
GENERALLY FAST WITH THE INTERNAL WAVE LEANING FORWARD AND
DEVELOPING THE SURFACE REFLECTION OVER VA AND OUT TO SEA A BIT
FASTER THAN MUCH OF THE GUIDANCE SUITE CONTINUES TO TREND A BIT
SLOWER WITH THE WAVE BUT ALSO IS MOST WRAPPED UP AND STRONGEST
WITH THE SURFACE REFLECTION BY 10/00Z SE OF NOVA SCOTIA.  THE 12Z
ECMWF WAS ALSO THE SLOWER AND SOUTHERN MODEL GENERALLY WITH A BULK
OF ITS ENSEMBLE MEMBERS FURTHER WEST AND ABOUT 3-6HRS SLOWER IN
DEVELOPMENT THOUGH HAVING A SIMILAR TRACK TO THE GFS...BUT THE
OPERATIONAL MODEL WAS ON THE EASTERN SIDE OF THE ECENS ENSEMBLE
PLOT NEARER TO THE REST OF THE GUIDANCE INCLUDING THE
GFS/NAM/UKMET.   THE 12Z CMC IS ON THE FAR EASTERN FRIDGE OF THE
ENSEMBLE PLOT WITH LARGE SPREAD IN ITS ENSEMBLE MEMBERS...IT IS
ALSO GENERALLY MUCH WEAKER WITH THE SURFACE REFLECTION AND TENDS
TO SHIFT ENERGY TO THE WAKE LOW NEAR CAPE COD ON WED MORNING...OUT
OF PHASE WITH MUCH OF THE OTHER GUIDANCE INCLUDING THE
ENSEMBLES...MAKING IT LESS DESIRABLE.  THE 12Z UKMET IS MUCH MORE
STABLE THAN THE CMC AND TRACKS WELL WITH THE GFS/ECMWF/NAM
SOLUTIONS INITIALLY BUT BEGINS TO BUCKLE THE TROF A BIT DEEPER
INTO THE SOUTHEAST BY WED MORNING AND IS THE FASTEST IN SHIFTING
THE WHOLE TROF OUT OF THE EASTERN US BY THE END OF THE PERIOD.
THE 00Z NAM TRACKS WELL PARTICULARLY WITH THE SLOWER 12Z ECENS
MEAN AND ECMWF THROUGHOUT THE FORECAST PERIOD...AND GIVEN ITS
HIGHER RESOLUTION MAY BE A BIT MORE AFFECTIVE IN SOME OF THE
MESOSCALE DETAILS BRINGING SOME ADDITIONAL CONFIDENCE IN A BLEND.
AS SUCH WILL SUPPORT A 00Z NAM/GFS AND 12Z ECWMF BLEND AT AVERAGE
CONFIDENCE OVERALL (THOUGH CONFIDENCE IN THE LARGE SCALE SYNOPTIC
SETUP MAY BE CLOSER TO ABOVE AVERAGE).


SHEARING SHORTWAVE BLEEDING INTO THE U.S. NORTHERN PLAINS WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

A SUBTLE FAST MOVING SHORTWAVE OVERTOPS THE STRONGER WESTERN RIDGE
TUESDAY ACROSS THE SW NORTHWEST TERRITORIES...EVENTUALLY DROPPING
ACROSS THE SOUTHERN CANADIAN PRAIRIES WITH LIGHT SNOWS INTO THE
NORTHERN RED RIVER VALLEY WED EVENING AND EVENTUALLY SHEARING
FULLY INTO THE FLOW OVER THE UPPER MIDWEST BY THURS.  THE 12Z
UKMET IS FLATTER WITH THE WAVE BUT WITH A TIGHTER GRADIENT AFTER
OVERTOPPING THE RIDGE IS STRONGER WITH INCREASED QPF AND FASTER
TRAJECTORY...ABOUT 12HRS FASTER THAN THE ENSEMBLE MEANS. THE 12Z
CMC SURFACE REFLECTION BACK OVER THE DAKOTAS IS QUITE DEEP AND
EXPANSIVE OUT OF PHASE WITH OTHER GUIDANCE AND FURTHER WEST THAN
EVEN THE EARLIER.  THE 00Z NAM DOES EJECT THE WAVE OVER THE TOP OF
THE RIDGE UNLIKE ITS PRIOR RUNS (18Z) BUT IS VERY WEAK AND SLOW
FAVORING THE 18Z GFS. THE 00Z GFS HOWEVER HAD TRENDED A BIT FASTER
NOW NEARING THE 12Z ECMWF SOLUTION/   THE 18Z GEFS/12Z ECENS MEAN
ARE IN FAIRLY GOOD AGREEMENT WITH THE 00Z GFS AND ECMWF. AS SUCH
WILL BLEND THE 00Z GFS/12Z ECWMF WHICH SHOULD RETAIN SOME OF THE
MAGNITUDE BUT STILL REPRESENTING THE GEFS/ECENS MEANS.  GIVEN THE
WEAKNESS OF THE FEATURE/SHEARING OUT AS WELL AS SPREAD IN
TIMING...CONFIDENCE IN THIS BLEND REMAINS ONLY AVERAGE.


SYSTEMS TRACKING THROUGH THE WESTERN PACIFIC TOWARD BRITISH
COLUMBIA/OLYMPIC PENINSULA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: AVERAGE

A STOUT RIDGE REMAINS A MAINSTAY FEATURE FOR MUCH OF THE EARLY TO
MIDDLE PART OF NEXT WEEK. MULTIPLE FEATURES DENT THE WESTERN SIDE
OF THE RIDGE AS EXTENSIONS OF LARGER GLOBAL CYCLONE OVER THE
CENTRAL NORTH PACIFIC.  THIS INCLUDES A LEAD WAVE NEARING
VANCOUVER ISLAND TUES EVENING/WED AND A SECOND LESS AMPLIFIED WAVE
LATE WED/THURS DRIVING MOISTURE FEED MAINLY INTO CENTRAL AND
SOUTHERN BC/VANCOUVER ISLAND EVENTUALLY SHIFTING SOUTH FOR
GLANCING AFFECTS INTO THURSDAY LEADING TO OROGRAPHIC ASCENT OVER
THE OLYMPIC PENINSULA.  ADDITIONALLY THESE WAVE PRODUCE SIMILARLY
TIMED SURFACE REFLECTIONS---THOUGH WELL OFF SHORE.  THE 12Z UKMET
IS A BIT MORE AMPLIFIED WITH THE INITIAL WAVE THOUGH FURTHER WEST
WITH THE TOP OF THE WAVE/MAIN VORT CENTER...DISPLACING THE SURFACE
REFLECTION WELL WEST AS WELL AND IS ALSO MUCH STRONGER WITH THE
SECONDARY WAVE/WAKE LOW.  OTHERWISE THE TIMING/AMPLIFICATION OF
THE WAVES ARE IN STRONG ENOUGH AGREEMENT WITH ENSEMBLE MEANS TO
SUPPORT A NON-UKMET BLEND AND THOUGH THE DETERMINISTIC MODELS ARE
WELL AGREED UPON FOR THIS ITERATION...DAY TO DAY ENSEMBLE ANALYSIS
SHOWS THE HIGH VARIATION WITHIN THE SOLUTION TO KEEP CONFIDENCE
ONLY AVERAGE ATTM.


...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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