Prognostic Meteorological Discussion
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048
FXUS10 KWNH 271850
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 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/ECMWF 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.

19Z UPDATE: THE 12Z CMC TRENDED MUCH MORE FAVORABLY TOWARD A
CONSENSUS IN TIMING PARTICULARLY WITH THE ECMWF.  THIS WHILE THE
12Z UKMET TRENDED AWAY FROM THE CONSENSUS IS VERY FLAT AND FAST
MAKING IT THE CLEAR OUTLIER.  THE 12Z ECMWF TRENDED A BIT DEEPER
TOWARD BETTER AGREEMENT WITH THE GFS IN TIMING/DEPTH WHICH
TRANSLATES WELL INTO NEW ENGLAND BY FRIDAY. WHILE THE CMC IS FINE
TO REPLACE THE UKMET IN THE PREFERENCE...THE TIGHTER AGREEMENT AND
A TREND TOWARD THIS COMMON SOLUTION FAVORS A 12Z GFS/ECMWF BLEND
AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.


DEEP LAYERED CYCLONE DESCENDING FROM WESTERN CANADA INTO THE
NORTHERN PLAINS EARLY FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY BELOW 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.

19Z UPDATE: THE 12Z UKMET HAVING TRENDED MUCH FLATTER WITH THE
PRECEDING WAVE AS SIGNIFICANTLY DEPARTED DEVELOPMENT LEADING TO
CONVECTIVE FEEDBACK AND UPSCALE DEEPENING FROM SAID CONVECTION
THURSDAY NIGHT INTO FRIDAY WHICH ALSO MANIFESTS AS A DEEP LEFT
TURNING SURFACE REFLECTION.  THE 12Z ECMWF/CMC BOTH TRENDED FASTER
BUT WITH EACH PIECE OF THE PUZZLE...WHICH ACTUALLY LEADS TO LESS
INTERACTION OF THE ARCTIC WAVE AND THE S CANADIAN WAVE ON THURS.
THIS FURTHER COMPOUNDS ON FRIDAY AS THE S CANADIAN TROF DROPS INTO
THE UPPER MS VALLEY BY 00Z SAT...FURTHER SOUTH AND SLIGHTLY FASTER
THAN THE 12Z RUN OR SUPPORTED BY THE 12Z ECENS MEAN AND A MUCH
GREATER SPREAD BETWEEN THE GFS/NAM IN THE LOWER LEVELS/QPF SIDE
THE GFS/ECMWF EVOLVE SIMILARLY WITH THE SHORTWAVE UNDERCUTTING THE
S CANADIAN WAVE SUPPORTING A WEAK SURFACE WAVE FROM N MO ON EARLY
FRIDAY TO MI BY 00Z...MAKING NO REAL DIFFERENCE FOR SENSIBLE
WEATHER/QPF.  HOWEVER...MASS IS QUITE DIFFERENT AS THE GFS (HAVING
THE DEEPER/CLOSED LOW) SPOTS A SURFACE REFLECTION NEAR THE N RED
RIVER; AND WITH INCREASED MASS SPREAD A PREFERENCE SHOULD BE
SELECTED.   GIVEN THE 12Z GFS SHOWS A FAST ABSORPTION/COMBINING OF
THE ARCTIC/CANADIAN WAVES...THIS SEEMS A BIT ON PAR WITH ITS KNOWN
FAST BIAS.  AS SUCH WILL FAVOR AN ECMWF/CMC BLEND FOR THE MASS
FIELDS...PLEASE REFER TO QPFPFD FOR ADDITIONAL DETAILS.
CONFIDENCE IS REDUCED TO SLIGHTLY BELOW AVERAGE IN A 12Z ECMWF/CMC
BLEND GIVEN THE LARGE SPREAD AND HIGH CONTINGENCY IN THE
TIMING/INTERACTION ACROSS CENTRAL CANADA WED INTO THURS.


LOW- TO MID-LEVEL WEAKNESS ACROSS THE WESTERN GULF OF MEXICO
LIFTING THROUGH SOUTHEAST/CAROLINAS THURS/FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE 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.

19Z UPDATE: THE 12Z CMC HAS A SIMILAR TIMING/EVOLUTION AND
PLACEMENT WITH THE MID-LEVEL TROF ALONG THE GULF COAST TOWARD THE
CAROLINAS.  THE 12Z UKMET TREND ED A BIT WEAKER TOO TO BECOME MORE
ALIGNED WITH THE ECMWF/CMC.  AS SUCH ONLY THE NAM LOOKS A BIT OUT
OF PLACE AND PERHAPS A BIT TOO DEEP ALONG THE ELONGATED TROF.  AS
SUCH A NON-NAM BLEND CAN BE SUPPORTED WITH SLIGHTLY ABOVE AVERAGE
CONFIDENCE.


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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