Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4

000
FXUS10 KWNH 220647
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 AM EST WED FEB 22 2017

VALID FEB 22/0000 UTC THRU FEB 25/1200 UTC

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

00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SOUTHERN STREAM CLOSED LOW EVOLUTION FROM THE GULF COAST TO THE FL
KEYS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND (NON-NAM OFFSHORE FRI/SAT)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOES-E WV LOOP CONTINUES TO DENOTE AN ELONGATED UPPER LOW ALONG
THE LOWER MS RIVER VALLEY WITH BROAD DIFFLUENCE SHIELD ACROSS THE
NORTHEAST GULF OF MEXICO.  EMBEDDED IN THE UPPER LOW AXIS...IS A
LOBE OF VORTICITY THAT IS JUST SOUTH OF LA THAT WILL BECOME THE
DOMINANT FEATURE THAT WILL CORRAL THE SURFACE LOW THROUGH SOUTH FL
AS IT WILL WOBBLE ALONG THE SE COAST NEAR THE NW BAHAMAS IN WAIT
FOR THE MAIN VORT FEATURE TO BOTTOM OUT THROUGH THE MEAN TROF AND
START TO FILL LATE THURS.   AFTER THURSDAY THE WEAKENING WAVE WILL
LIFT NORTHEAST TOWARD BERMUDA AND CONTINUE TO WEAKEN INTO EARLY
SAT.  OVERALL THE GUIDANCE HAS BEEN QUITE AGREEABLE WITH THE
OVERALL PATTERN WITH SMALL DIFFERENCES WITH SPECIFIC DETAILS SUCH
AS EXACT POSITION OF THE SURFACE LOW AS IT WOBBLES OFF THE FL
COAST.  FOR EXAMPLE THE 00Z NAM REMAINS SLOWER TO LIFT OUT THE
REMAINING TROF ENERGY FRI INTO SAT AND KEEPS THE SURFACE LOW
SUPPRESSED SOUTH AND EAST WHILE THE REST OF THE GUIDANCE LIFTS
NORTHEAST ALONG THE GULF STREAM.    LIKEWISE THE 00Z GFS IS A BIT
STRONGER AND RETAINS THE ENERGY TO THE UPPER LOW LEADING THE
FEATURE TO LAG THE NON-NCEP SOLUTIONS FRIDAY INTO SAT BUT THIS
APPEARS WELL WITHIN THE OVERALL ENSEMBLE TO BE MINOR.  AS SUCH
OVERALL A GENERAL MODEL BLEND CAN BE SUPPORTED FOR THE CONUS BUT
OFFSHORE WATERS ON FRIDAY MAY BE BEST SUPPORTED BY A NON-NAM
BLEND.  CONFIDENCE IS QUITE HIGH IN THIS EVOLUTION BUT GIVEN THE
INCREASED SPREAD TOWARD THE WEAKENING/FILLING STAGE ON FRIDAY...IS
REDUCED SLIGHTLY TO SLIGHTLY ABOVE AVERAGE.

07Z UPDATE: THE 00Z ECMWF TRENDED A BIT WEAKER AND THEREFORE IS A
BIT FASTER LIFTING OUT ON FRIDAY INCREASING THE SPREAD WITH THE
SLOWER GFS.  THIS WAS ACCOMPANIED BY THE 00Z CMC...WHILE THE UKMET
TRENDED A BIT DEEPER SUPPORTING THE GFS.  OVERALL THIS MAINTAINED
A SMALL TO MODERATE SPREAD BUT WILL KEEP WITH INITIAL PREFERENCE.


SHORTWAVE LIFTING OUT OF NORTHERN ROCKIES INTO THE UPPER MIDWEST
WITH ASSOCIATED SURFACE LOW...TRACKING ACROSS THE GREAT LAKES
EARLY THURS AND CLIPPING N NEW ENGLAND LATE THURS/EARLY FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOES WV MOSAIC SHOWS THE LEADING ELONGATED SHORTWAVE ENERGY ACROSS
THE BITTERROOTS/WESTERN MT MOUNTAIN RANGES BEGINNING TO EJECT INTO
THE NORTHERN HIGH PLAINS... SUPPORTING A WEAK SURFACE REFLECTION
IN SE MT ATTM.  THE 12Z ECMWF SHOWS A BIT WEAKER FLATTER SOLUTION
WITH THIS WAVE THAN THE REMAINING OPERATIONAL GUIDANCE AS IT
TRANSLATES ACROSS THE GREAT LAKES LATE WED INTO THURS.  THE 00Z
NAM SHIFTED TOWARD THIS FLATTER/FASTER SOLUTION AS WELL.  THE
GFS/UKMET WERE A BIT MORE AMPLIFIED AND SLOWER BUT STILL NOT TOO
FAR OFF...WITH THE 00Z GFS TRENDING A BIT FASTER THAN 12Z/18Z
RUNS.  THE 12Z CMC AS IS TYPICAL WAS SLOWER AND A BIT MORE
AMPLIFIED AND FURTHER SOUTH WITH THE TRACK OF THE SFC WAVE IN
COMPARISON.  OVERALL...THE TRENDS/WV MOSAIC SETUP SUPPORT THIS
FLATTER EVOLUTION AND WILL SUPPORT A HIGHER WEIGHTING TOWARD THE
ECMWF/NAM WITHIN A NON-CMC BLEND.  CONFIDENCE IS FAIRLY HIGH
(SLIGHTLY ABOVE AVERAGE) GIVEN THE OVERALL SPREAD IS SMALL TO
BEGIN WITH.

07Z UPDATE: THE 00Z CMC SHIFTED TO SOLID AGREEMENT WITH THE FASTER
ECMWF/NAM SOLUTIONS WHILE THE UKMET SLOWED COMPARED TO THE 12Z
RUN.  AS SUCH WILL SUPPORT A NON-UKMET BLEND.


BROAD LONGWAVE TROF CROSSING THE INTERMOUNTAIN WEST THURS/FRI
BEFORE CONSOLIDATING INTO A DEEP CLOSED LOW OVER MIDWEST LATE FRI
INTO SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/NAM/ECMWF
CONFIDENCE: AVERAGE

GOES-WEST WV LOOP DENOTES THE PIECES OF THE BROAD LONG WAVE TROF
ANCHORED OFF THE WEST COAST ARE IN PLACE FOR SHIFTING ASHORE AND
STARTING THE PROCESS OF CONSOLIDATING INTO AN INCREASING
CONCENTRIC DEEP LOW ACROSS THE MIDWEST BY FRIDAY.  IN THE WAKE OF
THE PRIOR SHORTWAVE...MODEST SHORTWAVE RIDGING BUILDS IN ACROSS
THE CENTRAL PLAINS INTO THURS ALLOWING FOR UPSTREAM STRONG
JET/SHORTWAVE ENERGY TO ACCELERATE THE WESTERN EDGE OF THE TROF
INTO THE INTERMOUNTAIN WEST.   THIS SUPPORTS A BIT OF NEGATIVE
TILT/HIGHLY DYNAMIC DIFFLUENCE TO SUPPORT RAPID SURFACE
CYCLOGENESIS OF THE SURFACE WAVE HOOKING OUT OF CENTRAL KS INTO IA
BY EARLY FRIDAY.   LAST FEW CYCLES OF ENSEMBLE SPAGHETTI ANALYSIS
SHOWS ALL THE PIECES COMING TOGETHER WITH THE DEEPER SOLUTION
POSED BY THE ECMWF/ECENS MEAN FIRST.  THE 00Z NAM/GFS HAVE TRENDED
TO THE ECMWF SOLUTION...BUT REMAIN A BIT NORTH WITH THE
DEFORMATION ZONE ACROSS THE IA/S MN WITH THE 00Z GFS HOLDING ON
THE STRONGER SURFACE/OCCLUDED LOW SOLUTION COMPARED TO THE 12Z
ECMWF FAVORING MORE TOWARD THE TRIPLE POINT INTO THE GREAT LAKES.
STILL THIS SEEMS MINOR AND WELL WITHIN THE PLAUSIBILITY TO SUPPORT
A BLEND OF THE THREE.  THE 12Z UKMET AND CMC ARE LAGGING AND SLOW
WITH THE UKMET BEING A BIT DEEPER.  CONFIDENCE IS INCREASED TO
AVERAGE BUT THE DEVIL REMAINS IN THE DETAILS.  PLEASE REFER TO THE
WPC QPFPFD AND QPFHSD (WINTER WEATHER/QPF DISCUSSIONS) FOR MORE
DETAILS.

07Z UPDATE: THERE WAS LITTLE SIGNIFICANT CHANGE IN THE ECMWF OR
CMC SOLUTIONS THOUGH THE 00Z UKMET TRENDED A BIT FASTER IT STILL
LAGS THE ENSEMBLE SUPPORTED ECMWF...BUT HAS TRENDED TO A MORE
SOUTHERLY TRACK LIKE THE ECMWF.  AS SUCH WILL KEEP A GFS/NAM AND
ECMWF SOLUTION BUT WILL CONTINUE TO WEIGHT THE ECMWF A BIT HEAVIER
IN THE BLEND OVERALL AS PREFERENCE.


PAIR OF SHORTWAVES FALLING DROPPING ALONG THE WESTERN CANADIAN
COAST TOWARD A MORE AMPLIFIED/PSBLY CLOSED UPPER LOW OFF THE
NORTHWEST COAST BY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

A COMPLEX SETUP WILL EVOLVE ACROSS THE NORTHEAST PACIFIC AS THE
DEEP UPPER LOW ALONG 40N NORTH OF HAWAII SHIFTS EAST AND THE DEEP
ANTICYCLONE TOWARD ITS NORTHEAST DIRECTS SHORTWAVE ENERGY ALONG
THE AK PENINSULA ALONG THE ENTIRE COAST OF AK BEFORE BREAKING WEST
OF HAIDA GWAII MOVING SOUTH...THIS WAVE EITHER SHIFTS WEST TOWARD
THE UPPER LOW OR SHEARS TOWARD THE EAST INTO PACIFIC NW AHEAD OF
THE NEXT DEEPENING SHORTWAVE THAT TRACKS ALONG THE BC COAST INTO
THE COASTAL WATERS OFFSHORE WA/OR BY SAT.  THIS SECOND WAVE
EVENTUALLY STARTS TO CLOSE OFF.   WHILE THE ENSEMBLE SPAGHETTI
PLOTS SHOW INCREASING CONVERGENCE TOWARD A COMMON SOLUTION OVER
THE PAST FEW CYCLES THERE REMAINS IMPORTANT DETAIL DIFFERENCES.
FOR EXAMPLE...THE ECMWF IS QUITE AGGRESSIVE IN SHEDDING THE BULK
OF ENERGY WEST TO THE UPPER LOW IN COMPARISON TO 00Z NAM SHEDDING
SOME TO THE 12Z UKMET/CMC AND 00Z GFS SHEDDING NO ENERGY
PREFERRING TO SWING THE SHEARED WAVE INTO THE PACIFIC COAST AND
GREAT BASIN BY FRI/SAT.   THIS ALSO LEAVES THE ECMWF HAVING LESS
INTERACTION BETWEEN THE TWO WAVES...AND THEREFORE A BIT CLOSER TO
THE COAST WITH THE SECOND CLOSING OFF WAVE.  A COMPROMISE WOULD BE
SOMETHING NEAR THE 18Z GEFS AND 12Z ECENS MEAN...WHICH MAY BE BEST
REPRESENTED BY THE 00Z NAM AND A BLEND OF THE 12Z ECMWF AND 00Z
GFS.   CONFIDENCE IS SLIGHTLY BELOW AVERAGE AS THERE ARE MANY
MOVING PARTS AND INTERACTIONS THAT ARE KEYED ON TIMING
DIFFERENCES...SO THE PREDICTABILITY IS A BIT TOO LOW TO HAVE
TREMENDOUS CONFIDENCE AT THIS TIME.

07Z UPDATE: SMALL CHANGES WITH THE ECMWF LEAD TO A SLIGHTLY
FURTHER WEST SOLUTION WITH THE SECOND WAVE (FURTHER FROM THE
COAST) AS WELL AS IT REMAINING AN OPEN WAVE THROUGH THE FORECAST
PERIOD....THE UKMET AND CMC BOTH TRENDED FAVORABLY TOWARD A COMMON
SOLUTION MIRRORING THE NAM FAIRLY WELL.  AS SUCH WILL FAVOR A
GENERAL MODEL BLEND AT THIS POINT...HOWEVER THE SPREAD REMAINS
FAIRLY LARGE PARTICULARLY GIVEN THE COMPLEXITY OF INTERACTIONS THE
ARE LIKELY BETWEEN THE WAVES.  STILL WITH TIGHTER AGREEMENT
CONFIDENCE IN A GENERAL MODEL BLEND IS NOW AVERAGE.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

GALLINA

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.