THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


MODEL DIAGNOSTIC DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 PM EDT MON JUL 24 2017

VALID JUL 24/1200 UTC THRU JUL 28/0000 UTC

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

12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...SHORTWAVE MOVING ACROSS THE GREAT LAKES/NORTHEAST
TODAY/TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

GOES-WV LOOP DEPICTS VERY ROBUST WAVE OVER SE ONTARIO WITH A
WEAKER S/W CROSSING N PA.  WHILE THE LARGE SCALE GUIDANCE IS A
SHADE SLOW WITH THE WEAKER S/W THERE IS SOLID AGREEMENT WITHIN THE
OVERALL GUIDANCE SUITE.  THE 12Z NAM IS SLIGHTLY DEEPER BUT HAS
TRENDED TOWARD CONSENSUS...OPPOSED TO THE RELATIVELY SHALLOW CMC. 
OVERALL THE DIFFERENCES ARE SMALL ENOUGH TO SUPPORT A GENERAL
MODEL BLEND AT ABOVE AVERAGE CONFIDENCE.

19Z UPDATE:  THE 12Z CMC BECOMES SOUTH OF THE MODEL CONSENSUS WITH
THE SURFACE LOW EAST OF MAINE BY TUESDAY AFTERNOON, BUT OTHERWISE
THE MODELS ARE IN VERY GOOD AGREEMENT WHILE THE SYSTEM IS OVER
LAND.  AFTER 36 HOURS, A NON-CMC BLEND IS PREFERRED GIVEN THE
DIFFERENCE NOTED.


...MID-LEVEL TROUGHING ACROSS THE GULF COAST SHIFTING TOWARD GA/SC
WED/THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: 12Z GFS/12Z ECMWF/12Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

CURRENT SATELLITE SUITE DEPICTS A MID-LEVEL WAVE OVER NE TX AND
MCV OVER E TX WITH A MID-LEVEL CONFLUENCE TROF EXTENDING ACROSS TO
ANOTHER MCV NEAR S MS.  GUIDANCE IS FAIRLY AGREEABLE IN THE
PLACEMENT OF THIS MAIN FEATURES EXTENDING TO THE WEAK TROF EXITING
THE CAROLINA/GA COAST TODAY.  THE 12Z NAM IS SLIGHTLY DEEPER WHICH
IS TO BE EXPECTED GIVEN ITS GRID SCALE RESOLUTION BUT REMAINS IN
PHASE WITH THE STRENGTH/PLACEMENT AND SHAPE OF THE WAVE AS IT
TRACKS SLOWLY THROUGH THE S CENTRAL GULF STATES TOWARD GA/SC
WED/THURS.    THE ONLY SIGNIFICANT DIFFERENCES SEEM TO MANIFEST
LATE WED INTO THURSDAY AS THE NAM AND 00Z UKMET BOTH SHOWING A BIT
SOUTHWARD PREFERENCE ALLOW FOR INCREASED SHEARING OF THE WAVE BACK
TOWARD THE SOUTHWEST INTO THE NORTHEAST GULF.  THIS IS OPPOSED TO
THE 12Z GFS/00Z ECMWF AND CMC THAT SEEM TO STALL OR PROPAGATE THE
MEAN WAVE TOWARD SC OR EVEN OFFSHORE BY EARLY THURS.  STILL THE
SPREAD IS REMARKABLY SMALL AND THEREFORE CONFIDENCE IS SLIGHTLY
ABOVE AVERAGE FOR A DAY 3 FORECAST GIVEN THE IMPORTANCE OF
CONVECTIVE PLACEMENT TO MAINTAIN/ENHANCE THE WAVE THROUGH
WED/THURS.  AS SUCH WILL SUPPORT A GENERAL MODEL BLEND THOUGH
INCREASE WEIGHTING TO THE MIDDLE GROUND SOLUTIONS OF THE 12Z
GFS/00Z ECMWF.

19Z UPDATE:  THE 12Z ECMWF TRENDED SLIGHTLY TO THE EAST WITH THE
TROUGH AXIS AT 700MB.  BY WEDNESDAY THE 12Z CMC IS EAST OF THE
MODEL CONSENSUS WHILST THE ECMWF HAS BETTER ENSEMBLE SUPPORT FOR
POSITION. 


...SYSTEM MOVING THROUGH SOUTHERN CANADA THROUGH WEDNESDAY
UNFOLDING TO ENCOMPASS THE GREAT LAKES BY THURS WITH ACCOMPANYING
SURFACE LOW FORECAST TO INTO THE UPPER MIDWEST BY THU MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/CMC/UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

CONFIDENCE REMAINS FAIRLY LOW THAN USUAL AS THERE IS INCREASING
SPREAD IN THE GUIDANCE WITH TWO DISTINCT CAMPS DEVELOPING...AN
INITIALLY DEEP MORE PHASED SOLUTION LATER THROUGH THE GREAT LAKES
INTO THURSDAY PRESENTED BY THE 12Z GFS AND LESSER SO THE 12Z NAM
OR THE INITIALLY FASTER AND LESS PHASED SLOWER SHORTWAVE CROSSING
THE GREAT LAKES BY THURSDAY PRESENTED BY THE ECMWF/CMC AND LESSER
SO THE UKMET.   ENSEMBLE SUITE CONTINUITY WOULD FAVOR THE GFS/NAM
THOUGH THERE IS AN INCREASING CLUSTER OF ECENS/CMCE MEMBERS THAT
SUGGEST A SHIFT IN GUIDANCE MAY BE OCCURRING.  

A VERY DEEP/CLOSED LOW CURRENTLY RESIDES JUST WEST OF THE CENTRAL
CANADIAN ROCKIES AND WILL CONTINUE TO TRANSLATE NEARLY DUE EAST
THROUGH WED. AT THIS POINT ONLY THE UKMET IS GENERALLY DISPLACED
RACING OUT FRONT OF THE REST OF THE GUIDANCE...THOUGH THE
UKMET/CMC/ECMWF ARE A BIT NORTH AND WEAKER THAN THE 12Z GFS/NAM.  
THIS NORTH/WEAKER BIAS ALLOWS FOR A FASTER TRANSLATION (CLIPPING
NORTHERN NEW ENGLAND)...AN UPSTREAM WAVE DEVELOPING OVER THE
SOUTHERN CANADIAN PRAIRIES IS THEREFORE ALLOWED TO AMPLIFY
SLIGHTLY MORE IN THE FAVORABLE ALIGNMENT ALOFT WHICH SLOWS ACROSS
THE WESTERN GREAT LAKES.  THE 00Z ECMWF/CMC AND ECENS MEAN ALL
SUGGEST THIS SLOWER/DEEPER AMPLIFICATION BY FRIDAY AND WHILE THE
UKMET OUTPACES SLIGHTLY THERE IS BETTER AGREEMENT HERE THAN WITH
THE GFS.  THE 12Z NAM WHILE INITIALLY STRONGER AND SLOWER CROSSING
EASTERN CANADA IS PHASED IN TIMING WITH THE TRAILING SHORTWAVE IN
THE GREAT LAKES PERHAPS TIPPING ITS HAND IN DEFERENCE TO THE
GROWING UPSTREAM CONSENSUS.  STILL THE NAM DOES SHOW SOME FAST
FORWARD PROPAGATION OF THE RESULTANT MCS ACROSS THE OH VALLEY ON
THURSDAY TO BE FULLY ALIGNED WITH THE ECMWF/UKMET/CMC.   THE 12Z
GFS DID NOT DEVIATE TOO MUCH FROM THE 00Z/06Z RUN RETAINING A
STRONG/SOUTHERN TRACK OF THE CLOSED LOW THROUGH SE
CANADA...HOWEVER THE UPSTREAM SHORTWAVE REMAINS VERY CLOSE IN
PROXIMITY AND GENERALLY PHASES ACROSS THE GREAT LAKES SHOWING ITS
FAST BIAS WITH THE TROF AXIS THROUGH THE GREAT LAKES ON THURSDAY. 
NOT THAT THE SREF IS RELIABLE...IT GENERALLY FALLS IN LINE WITH
THE 00Z ECENS MEAN.  OVERALL WILL SUGGEST A 00Z ECMWF/CMC/UKMET
BLEND BUT CONFIDENCE IS SLIGHTLY BELOW AVERAGE GIVEN SPREAD AND
POTENTIAL TRANSITION IN TIMING. 

19Z UPDATE:  THE 12Z NAM REMAINS MORE AMPLIFIED WITH THE 500MB
PATTERN COMPARED TO THE LATEST GUIDANCE.  THE 12Z ECMWF TRENDED
SLIGHTLY FASTER WITH THIS SYSTEM AND IS CLOSE TO THE MODEL
CONSENSUS, COMPARED TO THE FASTER GFS.


...CLOSED UPPER LOW NEAR CALIFORNIA THROUGH WED BEFORE LIFTING
NORTHEAST TOWARD ID THURS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND AFTER WEDNESDAY MORNING
CONFIDENCE: ABOVE AVERAGE

THE CLOSED LOW JUST OFF THE N CA COAST WILL LINGER THROUGH MUCH OF
THE FORECAST PERIOD UNTIL IT FEELS UPSTREAM KICKER WAVE INFLUENCE
LATE WED.  SO BY THURSDAY THE OVERALL TROF OPENS TOWARD THE
NORTHEAST AND LIFTS TOWARD THE WESTERN SNAKE RIVER PLAIN WITH
FAIRLY STRONG MODEL CONSENSUS.  THE ONLY STANDARD DETERMINISTIC
GUIDANCE MEMBER TO DEVIATE FROM STRONG CONSENSUS IS THE 00Z CMC
WHICH FOLLOWS ITS TYPICAL BIAS OF BEING A BIT TOO DEEP AND SLOW TO
WEAKEN THE WAVE...LEADING TO TIMING DIFFERENCES AS WELL BY THURS.
THE 12Z GFS DID SHOW A BIT OF A TREND TOWARD A DEEPER/SLIGHTLY
SLOWER SOLUTION COMPARED TO THE 00Z/06Z RUNS...THOUGH STILL NOT AS
DRAMATIC AS THE CMC.  AS SUCH A NON-CMC BLEND IS SUPPORTED AND
GIVEN THE OVERALL AGREEMENT AND CONTINUITY CONFIDENCE IS ABOVE
AVERAGE.

19Z UPDATE:  NO MAJOR CHANGES TO THE PREFERENCE EXCEPT THAT THE
12Z CMC IS CLOSE ENOUGH TO THE MODEL CONSENSUS TO INCLUDE THROUGH
48 HOURS.


...MID-LEVEL WAVE GROWING UPSCALE DEVELOPING TO GLOBAL TROF OVER
EASTERN GULF OF AK WITH AN EMBEDDED KICKER SHORTWAVE NEARING
PACIFIC NORTHWEST BY EARLY THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

A BINARY INTERACTION BETWEEN TWO FAIRLY ROBUST WAVES IN THE
CENTRAL GULF OF AK WILL DRIFT EASTWARD TOWARD THE S AK PANHANDLE/N
BC BY WED.  AN UPSTREAM DEVELOPING CLOSED WAVE IN BRISTOL BAY WILL
DROP INTO THE CENTRAL GULF OF AK BY THURSDAY TAKING OVER FOR THE
EXITING WAVE THROUGH BC...BUT IN COMBINATION THIS LEADS TO THE
UPSCALE DEVELOPMENT OF A GLOBAL TROF THAT DOMINATES THE NORTHERN
PACIFIC.  ON THE SOUTHERN PERIPHERY OF THIS TROF A PACIFIC
SHORTWAVE JUST NORTH OF 40N WILL TRANSLATE EASTWARD TOWARD THE
PACIFIC NORTHWEST (ACTIVELY KICKING THE CLOSED LOW...SEE ABOVE) BY
12Z THURS.  THE 00Z CMC IS QUITE SLOW IN COMPARISON TO THE MAIN
GUIDANCE AND IS CLEAR ENOUGH OUTSIDE THE MEAN ENSEMBLE ENVELOPE TO
IGNORE.  THE 12Z NAM ALSO TRENDS A BIT SLOWER AND WHILE ON THE
WESTERN EDGE OF THE ENSEMBLE SUITE LAGS SUFFICIENTLY TO THE 12Z
GFS/00Z ECMWF (WHICH CONTINUE TO POPULATE NEAR THE GEFS/ECENS
MEAN) TO BE INCLUDED.  THE 00Z UKMET IS A BIT MORE
SHEARED/ELONGATED THROUGH THE SE QUADRANT OF THE GLOBAL TROF (IE
LESS AMPLIFIED) BUT SEEMS A GOOD COMPROMISE FOR INCLUSION GIVEN
THE LIKELY RUN TO RUN VARIATION/MODEST SPREAD IN THE HEIGHT FIELDS
EXPERIENCED IN THIS UPSCALE GROWTH.  CONFIDENCE IN A 12Z GFS AND
00Z ECMWF/UKMET BLEND IS GOOD BUT MODEST SPREAD SUGGESTS THE
AVERAGE INTERVAL OVER THE SLIGHTLY ABOVE AVERAGE INTERVAL.  

19Z UPDATE:  THE 12Z ECMWF DID TREND SLIGHTLY MORE AMPLIFIED WITH
THIS FEATURE, BUT STILL CAN BE INCLUDED IN THE MODEL PREFERENCE. 
THE 12Z CMC LAGS BEHIND WITH THE TROUGH AXIS BY WEDNESDAY NIGHT
AND INTO THURSDAY, BUT IT IS USEFUL THROUGH THE FIRST 48 HOURS OF
THE FORECAST.


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





Last Updated: 321 PM EDT MON JUL 24 2017