Prognostic Meteorological Discussion
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FXUS10 KWNH 271646
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 PM EDT TUE JUN 27 2017

VALID JUN 27/1200 UTC THRU JUL 01/0000 UTC

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

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

TROUGH LIFTING THROUGH NEW ENGLAND TODAY/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

GUIDANCE INDICATES CONTINUED STRONG AGREEMENT TO SUPPORT A GENERAL
MODEL BLEND AT ABOVE AVERAGE CONFIDENCE THROUGHOUT TODAY AND WED.


WEAK SHORTWAVE MOVES THROUGH THE DAKOTAS TODAY AND INTO UPPER
MIDWEST/WESTERN GREAT LAKES BY WED/THURS AND INTO N NEW ENGLAND
FRIDAY/SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS AND 00Z ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE


SHORTWAVE TWIST CROSSING INTO SW MT CURRENTLY WILL CONTINUE TO
PROGRESS THROUGH THE ROCKIES AND TRANSLATE QUICKLY THROUGH THE
DAKOTAS TODAY BEFORE FINDING A WEAKNESS IN FLOW TO BEGIN TO AMPLY
WITH INCREASED NEGATIVE TILT AND PERHAPS A WEAK CLOSED LOW THROUGH
THE GREAT LAKES BEFORE SHEARING THROUGH NORTHERN NEW ENGLAND
FRIDAY.   THE CLEAR OUTLIER REMAINS THE 00Z CMC WHICH IS QUITE
SLOW AND TUCKED NW TOWARD THE DEEPER UPPER LOW IN CENTRAL CANADA.
THE 12Z NAM/GFS BOTH FIND A BETTER LARGER SCALE PATTERN ACROSS THE
WESTERN GREAT LAKES THURS TO AMPLIFY TO A TIGHT MID-LEVEL
SHORTWAVE.  THE GFS HAVING BEEN A BIT WEAKER THAN THE NAM ALREADY
FURTHER TRENDED WEAKER WITH THE 12Z RUN TOO.  THIS
TIGHTER/CONSOLIDATED WAVE EVOLUTION IS OPPOSED BY A FLATTER MORE
PROGRESSIVE SOLUTIONS PRESENTED BY THE UKMET (FASTER) AND ECMWF
(SLOWER). THE NAM/GFS DEEPER SOLUTIONS ARE SLOWER TO BREAK DOWN
THE WAVE AND PROGRESS IT THROUGH NEW ENGLAND ON FRIDAY.   AS SUCH
WILL HEDGE PREFERENCE TOWARD A MIDDLE GROUND AWAY FROM THE DEEP
NAM/SLOW CMC AND FAVOR A GFS/ECMWF/UKMET BLEND AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.


DEEP LAYERED CYCLONE DESCENDING FROM WESTERN CANADA INTO THE
NORTHERN PLAINS EARLY FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

MULTIPLE MOVING PARTS LEADS TO A COMPLEX EVOLUTION ACROSS CENTRAL
CANADA INTO THE NORTHERN GREAT PLAINS BY THURSDAY LEAKING INTO THE
WESTERN GREAT LAKES/UPPER MS VALLEY BY LATE FRIDAY.  INTERESTINGLY
THE DIFFERENCES PARTICULAR ALOFT DO NOT LEAD TO LARGE DEPARTURES
IN IMPACTING SENSIBLE WX RELATIVELY SPEAKING TOWARD DAY 3.  THE
TIMING/COMBINATION OF THE SHORTWAVE FEATURE COMING OUT OF THE
ARCTIC STREAM AND ROTATING AROUND THE NORTHERN PERIPHERY OF THE S
CENTRAL CANADIAN WAVE LEAD TO THIS LARGER SPREAD ALOFT.  THE
ECMWF/ECENS MEAN SUGGESTS A SLOWER TIMING AND THEREFORE DO NOT
COMBINE THE WAVES SUGGESTING A WEAKER SHORTWAVE INTO THE DAKOTAS
FRIDAY.  GIVEN THIS SLOWER TIMING...AN UNDERCUTTING SHORTWAVE
(ORIGINATING OVER BC/N ROCKIES WED/THURS) IS ABLE TO AMPLIFY
FRIDAY NIGHT OVER WI.   THE 00Z CMC SHOWS SOME SIMILARITY TO THIS
EVOLUTION PROVIDING SOME CONFIDENCE IN THE EVOLUTION.   THE 12Z
NAM/GFS ON THE OTHER SIDE OF THE TIMING SPECTRUM ARE QUICKER AND
TRAVERSE ENERGY TO THE CLOSED LOW OVER SOUTHERN CANADA BY LATE
THURSDAY...WHICH FURTHER EXPANDS AND SETTLES INTO THE DAKOTAS WITH
A FLATTER REFLECTION ROTATING AROUND THE BASE INTO THE UPPER MS
VALLEY IN COMPARISON TO THE ECMWF/CMC.  THE 00Z UKMET SEEMS TO
FILL THE MIDDLE OF THE SPECTRUM...NEARLY SPLITTING AN EQUITABLE
DIFFERENCE.  OVERALL TIMING/EVOLUTION APPEARS CONTINGENT ON THIS
INTERACTION AND TO WHAT MAGNITUDE AND THAT IS VERY DIFFICULT TO
LOCK DOWN ESPECIALLY OUT OF THE DATA SPARSE N CANADA/ARCTIC
STREAM.  STILL GIVEN THE DIFFERENCES ARE MINOR ON SENSIBLE WX A
GENERAL MODEL BLEND IS PREFERRED...FAVORING TOWARD THE ECMWF/UKMET
SLIGHTLY IN WEIGHTING THOUGH GIVEN THE SPREAD CONFIDENCE IS ONLY
AVERAGE.


LOW- TO MID-LEVEL WEAKNESS ACROSS THE WESTERN GULF OF MEXICO
LIFTING THROUGH SOUTHEAST/CAROLINAS THURS/FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

CURRENTLY A WEAK UPPER SHORTWAVE/INVERTED LOW LEVEL TROF IS
AFFECTING THE WESTERN GULF COAST... GUIDANCE IS PERSISTENT IN THE
GENERAL ENE TRACK OF THE WAVE THROUGH THE END OF THE WORK WEEK BUT
THERE REMAINS SUFFICIENT TIMING DIFFERENCES AS WELL AS EVOLUTION
OF THE FEATURE.   THE 12Z NAM/GFS CONTINUE TO SHOW THE FLATTEST
TREND WITH A INCREASED ELONGATION OF THE WAVE/VORT FEATURE
TRACKING THROUGH THE CENTRAL GULF EARLY THURSDAY TOWARD THE
CAROLINAS BY FRIDAY.  THE 12Z NAM SHOWS STRONGER/DEEPER FEATURES
THROUGH THE WAVE LIKELY AS A RESPONSE TO CONVECTION AS WELL AS ITS
FINER GRID SCALE...BUT OVERALL APPEARS A BIT AGGRESSIVE.  THE 12Z
SHOWS LITTLE CHANGE FROM PRIOR RUNS BUT SEEMS QUITE REASONABLE
GIVEN LARGER SCALE FLOW PATTERN.

THIS FLATTER EVOLUTION IS OPPOSED TO THE ECMWF/UKMET/CMC THAT
SUGGEST A BIT MORE CONSOLIDATION OF THE WAVE...HOWEVER, BOTH CAMPS
MAINTAIN SOME LINGERING ENERGY THROUGH THE CENTRAL GULF BY THE END
OF THE FORECAST PERIOD.  THE 00Z ECMWF SHOWS GOOD TIMING WITH THE
GFS/NAM BUT IS MUCH MORE CONSOLIDATED WITH THE WAVE AND APPEARS
MOST MIDDLE GROUND OF SOLUTIONS.  THE 00Z CMC IS SIMILAR TO BOTH
THE GFS/ECMWF AS A COMPROMISE IN EVOLUTION BUT AS TYPICAL TO THE
CMC, IS MUCH TOO SLOW ON ANY PIECE OF THE TROF TO FAVOR ITS
INCLUSION.  THE 00Z UKMET IS MOST AGGRESSIVE OF THE AMPLIFIED
GUIDANCE AND IN DOING SO IS SLOWER WITH THE WAVE ENTERING THE
SOUTHEAST/CAROLINAS LATER IN THE WEEK; THIS ALSO MAKES IT QUITE
SLOW EVEN SLOWER THAN THE ECMWF, VERY UNCHARACTERISTIC.   AS SUCH
A 12Z GFS/00Z ECMWF SOLUTION SEEMS APPROPRIATE.  CONFIDENCE
(MAINLY IN THE INFLUENCE OF CONVECTION) IS CONSIDERED AVERAGE IN
THIS BLEND.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

GALLINA

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