Prognostic Meteorological Discussion
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000
FXUS10 KWNH 250405
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1104 PM EST FRI FEB 24 2017

VALID FEB 25/0000 UTC THRU FEB 28/1200 UTC

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

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

MID-LEVEL SHORTWAVE ACQUIRING A NEGATIVE TILT ACROSS THE LOWER
GREAT LAKES AND NORTHEAST SAT/SAT NIGHT
COLD FRONT MOVING THROUGH THE MIDWEST TONIGHT INTO SAT AND THROUGH
THE EAST COAST ON SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

MODELS INCLUDING THE 00Z NAM/GFS SHOW VERY TIGHT MASS AGREEMENT IN
PLACEMENT/STRENGTH AND TIMING OF THE MEAN SHORTWAVE TROF AND
ASSOCIATED SURFACE COLD FRONT TRANSLATING ACROSS THE EASTERN OH/TN
VALLEY TONIGHT AND THROUGH THE EAST COAST TOMORROW AND FAR
NORTHEAST EARLY SUN.   THIS AGREEMENT IS SOLID ENOUGH TO SUPPORT
GENERAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE.


FAST MOVING MID-LEVEL SHORTWAVE TRACKING FROM THE NRN PLAINS SAT
EVENING TO THE GREAT LAKES SUN EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A FAIRLY QUICK MOVING KICKER CLIPPER SHORTWAVE AND ASSOCIATED WEAK
SURFACE REFLECTION ENTERS MT/ND LATE SAT AND TREKS THROUGH THE NW
GREAT LAKES SUNDAY UNDER FAIRLY SOLID AGREEMENT IN TIMING/STRENGTH
AND PLACEMENT OF THE MAIN MASS FEATURES.  THE 00Z GFS IS GENERALLY
A BIT DEEPER AND SLIGHTLY FASTER THAN THE REMAINING GUIDANCE BUT
NOT SIGNIFICANTLY SO TO REMOVE IT FROM THE PREFERENCE.  STILL IT
MAY PRUDENT TO GIVE A LITTLE BIT LOWER WEIGHTING KNOWING THIS
MATCHES WITH TYPICAL GFS BIAS, YET A GENERAL MODEL BLEND SHOULD
SUFFICE AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.


SHORTWAVE SLIDING SOUTH OFF OF THE WEST COAST SAT AND REACHING THE
SRN PLAINS LATE SUN AND SHEARING INTO THE CONFLUENT FLOW ACROSS
THE CENTRAL US MON INTO TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET AND 00Z NAM BLEND
CONFIDENCE: AVERAGE

THE LARGE MODEL SPREAD HAS SIGNIFICANTLY REDUCED NOW THAT THE
CRITICAL INTERACTION WITH THE WELL OFFSHORE UPPER LOW NORTHEAST OF
HAWAII HAS OCCURRED WITH REDUCED INFLUENCE TO SHORTWAVE CURRENTLY
DROPPING SOUTH ALONG THE WEST COAST.  THIS HAS ALLOWED FOR THE
MORE PROGRESSIVE TRACKING OF THE UPPER LOW SUGGESTED BY THE
ECMWF/GFS LAST NIGHT AND THE SUBSEQUENT RUNS HAVE FURTHER
SOLIDIFIED ON A COMMON SOLUTION PROVIDING MUCH INCREASED
CONFIDENCE AND REDUCED SPREAD.   STILL THERE REMAINS SOME MINOR
DIFFERENCES THAT WILL PLAY CRITICAL ROLES IN THE RETURN FLOW OUT
OF THE WESTERN GULF SPURRING WIDE SPREAD ASCENT AND PRECIPITATION
OVER THE LOWER MS RIVER VALLEY INTO THE SOUTHEAST MON INTO TUES.
PLEASE REFER TO QPFPFD FOR ADDITIONAL MODEL PREFERENCES WITH
RESPECT TO THE QPF.   AS FOR MASS...THERE IS FAIRLY GOOD TIMING
THROUGH ABOUT 12Z SUNDAY BUT THE 00Z GFS SHOWS A BIT QUICKER
SHEARING OF THE WAVE INTO THE FOUR CORNERS REGION SHOWING
INCREASED PHASING/CONNECTION TO THE NORTHERN STREAM WAVE...THIS
ALLOWS FOR A SLIGHTLY FASTER TRANSITION OF THE WAVE TO SHEAR INTO
THE CONFLUENT FLOW ACROSS THE CENTRAL PLAINS OPPOSED BY THE
SLIGHTLY DEEPER/CONCENTRIC BASE SOLUTIONS PRESENTED BY THE 12Z
ECMWF/UKMET...THAT EVENTUALLY ARE SLOWER TO SHEAR AND RETAIN A
FURTHER SOUTH TRACK OF THE MAIN WAVE.   WHILE THE ECMWF/UKMET ARE
SLOWEST THE 00Z NAM IS CLOSER IN TIMING/PROXIMITY AND SHAPE TO
THOSE SOLUTIONS THAN THE GFS.  THE 12Z CMC IS MORE FAVORABLE TO
GFS SOLUTION.

OVERALL THESE MINOR DETAIL DIFFERENCES ARE QUITE SMALL AND
POTENTIALLY A BIT TOO PICKY GIVEN THE OVERALL EVOLUTION IS MUCH
BETTER AGREED UPON...AS SUCH THE CONFIDENCE IS MUCH HIGHER AS WELL
TO THE OVERALL PATTERN TAKING PLACE BUT STILL MODEST GIVEN THE
SMALL DETAILS HAVE MODERATE SENSIBLE WX DIFFERENCES MON INTO TUES.
 AS SUCH A 12Z ECMWF/UKMET BLEND WITH SOME INCLUSION OF THE 00Z
NAM IS PREFERRED AT AVERAGE CONFIDENCE.


NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO NW US COAST SUNDAY
INTO MON PHASING WITH OFFSHORE UPPER LOW THAT WILL SWING THROUGH
SOUTHERN CA BY TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

THE PRECEDING WAVE STARTED CARVING OUT THE MEAN LARGER SCALE TROF
OVER THE WEST BUT THE NEXT WAVE DESCENDING THE EAST SIDE OF THE
DOMINATING GULF OF AK ANTICYCLONE WILL AMPLIFY INTO SUN OFF THE WA
COAST AND BROADEN WITH TIME AS IT TRACKS SOUTHEAST INTO THE GREAT
BASIN WITH SOLID MODEL AGREEMENT. THROUGH MUCH OF MONDAY.   THE
SPREAD MAINLY EXISTS WITH THE MAGNITUDE INTERACTION/CONNECTION TO
THE DEEP OFFSHORE UPPER LOW BECOMING THE PHASED BASE OF THE TROF
ENTERING SOUTHERN CA TOWARD THE END OF THE FORECAST PERIOD.  AN
UPSTREAM KICKER WAVE WILL ALSO ENTER THE PACIFIC NORTHWEST LATE
MON INTO EARLY TUES TO FURTHER EXPAND THE LARGER SCALE TROF WHILE
KICKING THE LEAD ENERGY OUT ACROSS THE NORTHERN ROCKIES SPURRING
LEE SURFACE CYCLOGENESIS OUT OF E CO ON MONDAY NIGHT/TUESDAY
MORNING.  THE 00Z NAM APPEARS TO BE THE ONLY MAIN DETERMINISTIC
GUIDANCE MEMBER THAT RETAINS A DEEPER MORE CONSOLIDATED UPPER LOW
OVER AND LIMITS THE EASTWARD PROGRESSION OF THE FEATURE TOWARD
SOUTHERN CALIFORNIA.  THE 12Z CMC IS FAIRLY QUICK TO BREAK DOWN
AND EJECT THE LEAD SHORTWAVE THROUGH THE INTERMOUNTAIN WEST BY
LATE MON INTO TUESDAY IN FAVOR OF A DEEPER KICKER FEATURE WHICH
SEEMS LESS LIKELY WITHIN THE ENSEMBLE SUITE WHICH HAVE BEEN FAIRLY
CONSISTENT IN THIS WAVES EVOLUTION/TIMING.   THE 00Z GFS/ECMWF AND
UKMET SEEM TO EVOLVE IN A VERY SIMILAR MANNER PROVIDING OVERALL
CONFIDENCE TO THE SITUATION HOWEVER...BY DAY 3 THE 00Z GFS
CONTINUES TO BE SLIGHTLY FASTER WITH THE MEAN TROF AXIS BY
COMPARISON AND FALLS OUT OF PREFERENCE/OVERALL ENSEMBLE SUPPORT.
AS SUCH A 12Z ECMWF/UKMET BLEND REMAINS PREFERRED AT AVERAGE
CONFIDENCE.

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

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

GALLINA

$$





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