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171
FXUS10 KWNH 161832
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EST THU NOV 16 2017

VALID NOV 16/1200 UTC THRU NOV 20/0000 UTC

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

12Z MODEL PREFERENCES WITH CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SYSTEM LEAVING NEW ENGLAND TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE 00Z UKMET ONCE AGAIN LAGS THE OVERALL CONSENSUS AS THE
SURFACE/STACKED LOW LIFTS INTO SE CANADA FRI. OTHERWISE...THERE
REMAIN SOME LINGERING DEPTH DISCONTINUITIES (2-3 MB AT THE
SURFACE) THE PLACEMENT/SHAPE LOOK STRONG ENOUGH TO SUPPORT A
NON-UKMET BLEND AT ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: 12Z UKMET RUN WHILE STILL A BIT SLOWER THAN THE OTHER
GUIDANCE IS NOW WELL WITHIN THE TIGHT CLUSTERING TO SUPPORT A
GENERAL MODEL BLEND.


NORTHERN STREAM S/W AND CYCLONE LIFTING ACROSS SOUTHERN CANADA
WITH COLD FRONT MOVING THROUGH NORTHERN TIER TODAY TO SAT MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE LEAD SHORTWAVE/HEIGHT FALLS FROM THE MAIN UPPER LOW ALONG THE
WEST COAST IS CURRENTLY CROSSING INTO THE US/CANADIAN BORDER
ROCKIES OUT OF E WA...MODELS HAVE COME INTO A NEAR CONSENSUS WITH
ITS FUTURE EVOLUTION INCLUDING THE LEE SURFACE CYCLONE.  THIS WAVE
WILL TRACK FROM S ALBERTA TODAY TO NE MANITOBA BY LATE FRIDAY
BEFORE SHOWING ANY REAL DIFFERENCES/DEPARTURES.   THIS INCLUDES
THE TIMING OF THE FRONTAL ZONE CROSSING INTO THE GREAT LAKES AND
CONNECTING BACK TO THE DEVELOPING CENTRAL PLAINS LOW.   AS SUCH
WILL SUPPORT A GENERAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: NO SIGNIFICANT CHANGE NOTED IN THE 12Z UKMET/CMC/ECMWF
OR GEFS MEAN TO SUGGEST CHANGE TO THE GENERAL MODEL BLEND
PREFERENCE.


CYCLONE MOVING FROM CENTRAL PLAINS TO GREAT LAKES TO NEW ENGLAND
FRI...SAT...SUN WITH ATTENDANT FRONTAL ZONE THROUGH THE SOUTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE

OVERALL EVOLUTION OF THE BASE OF THE LARGE WESTERN TROF CONTINUES
TO CONSOLIDATE BUT SMALL BUT IMPORTANT DIFFERENCES CONTINUE TO
LEAD TO MODERATE SPREAD PARTICULARLY TOWARD THE PRECISE
LOCATION/TRACK OF THE SURFACE WAVE AND THE TIMING OF THE ATTENDANT
COLD FRONT ESPECIALLY ON SUN.  THE 12Z NAM AND GFS BOTH SHIFTED
SOUTH WITH THE TRACK WHILE BROADENING THE OVERALL WAVELENGTH OF
THE TROF (BEGINNING TO BE ROUNDER AS IT LIFTS OUT OF THE OH/TN
VALLEY INTO NEW ENGLAND.  THIS IS OPPOSED BY A MORE ELONGATED
EMERGENCE LIFTING NORTH BY THE ECWMF/CMC AND UKMET. THE 00Z CMC
LOOKS MOST OF OF PLACE IS COMPARISON PLOTS BEING A BIT TOO FAST
ESPECIALLY IN TIMING OF THE COLD FRONT THROUGH THE SOUTH AND AS
SUCH WILL BE REMOVED FROM ANY PREFERENCE AT THIS TIME.  A NON-CMC
BLEND SHOULD SUFFICE AT THIS TIME BUT MODEST MASS SPREADS WITH THE
LOW TRACK CONFIDENCE IS AVERAGE IN THIS BLEND.

19Z UPDATE: THE 12Z CMC SLOWED THE INNER CORE OF THE UPPER LOW BUT
CONTINUES TO PRESENT A STRONG COLD CONVEYOR/JET THAT PRESSES THE
COLD FRONT A BIT TOO FAST THROUGH THE MID-ATLANTIC/CAROLINAS AND
SOUTHEASTERN TIER STATES.  THE 12Z ECMWF SLOWED A BIT...LIKE THE
GFS/NAM ALLOWING FOR ADDITIONAL TIME TO TIGHTEN/AMPLIFY ACROSS THE
GREAT LAKES...TRACK FURTHER SOUTH AND SLOW THE FRONTAL TIMING A
SHADE.  STILL THIS IS QUITE CLOSE TO THE GFS.  THE 12Z UKMET IS
THE LONE GUIDANCE MEMBER TO NOT MAKE THE SLIGHT SOUTHWARD
SHIFT...YET STILL REMAINS CLOSE/CLUSTERED AND TIMED WELL WITH THE
GFS/NAM/ECMWF TO KEEP A NON-CMC BLEND.


TROUGH AND SURFACE WAVE APPROACHING VANCOUVER ISLAND LATE SAT WITH
FRONTAL ZONE SLIPPING INTO NW BY LATE SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

BY FRIDAY A SHORTWAVE BEGINS TO AMPLIFY ACROSS THE GULF OF AK AND
DRAW SOME SOUTHERN ENERGY INTO IT BROADENING THE TROF BY SAT AS IT
SLOWLY DROPS TOWARD THE PACIFIC NORTHWEST.  CORRALLED BY A SURFACE
WAVE LIFTING NORTHEAST INTO CENTRAL BC BY 00Z SUN...THE MOISTURE
TONGUE WILL BEGIN TO PULL NORTHWARD AS WELL AND BY SUNDAY WILL BE
DIRECTED TOWARD VANCOUVER ISLAND.  IT IS IN THE INTERACTION TIMING
AND STRENGTH OF THE SOUTHERN WAVE THAT GENERALLY LEADS TO MODEST
MODEL SPREAD TOWARD SAT/SUN AND HOW FAST/STRETCHED IT BECOMES AS
IT PROGRESSES SOUTHEAST.   THE BULK OF ENSEMBLE SOLUTIONS ARE
TRENDING TO A SHARPER SOLUTION WITH MODEST POSITIVE TILT
ORIENTATION.  THE 00Z CMC IS A BIT MORE AGGRESSIVE/STRONG IN THE
SOUTHERN PORTION OF THE TROF BY SUNDAY AND PRESSES THE BASE`S
HEIGHT FALLS FORWARD FASTER.  THE GFS WHICH HAD BEEN LAGGING
SIGNIFICANTLY HAS TRANSITIONED FASTER TO BECOME MUCH CLOSER TO THE
 OTHERWISE AGREEABLE  12Z NAM AND 00Z ECMWF/UKMET REPRESENTING THE
 THE MIDDLE OF THE MODEST ENSEMBLE SPREAD. A SLIGHT EASTWARD SHIFT
AT THE NORTHERN PORTION OF THE TROF BY 00Z MON WAS NOTED IN THE
12Z NAM RUN RELATIVE TO THE GFS/UKMET/ECMWF BUT SEEMS MINOR IN FOR
A DAY 3 TO KEEP IT WITHIN THE OVERALL PREFERENCE.  AS SUCH A
NON-CMC BLEND IS SUGGESTED WITH GREATEST WEIGHTING TOWARD THE
ECWMF.  CONFIDENCE IS SLIGHTLY ABOVE AVERAGE.

19Z UPDATE: THE 12Z CMC WHILE STILL A SHADE FASTER AND LESS
ELONGATED TOWARD THE SOUTHWEST TOWARD LATE SUNDAY IS CLOSE ENOUGH
TO FURTHER TIGHTEN THE GUIDANCE CLUSTER/EVOLUTION.  LITTLE
VARIATION IN THE ECMWF FURTHER SOLIDIFIES AND INCREASES CONFIDENCE
IN A GENERAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE AT THIS TIME
OUT INTO THE FUTURE.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

GALLINA

$$





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