Prognostic Meteorological Discussion
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000
FXUS10 KWNH 251849
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 PM EDT SUN JUN 25 2017

VALID JUN 25/1200 UTC THRU JUN 29/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...LONGWAVE TROUGH MOVING ACROSS THE EASTERN U.S....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 60 HOURS
            NON-NAM CONSENSUS...AFTER 60 HOURS
CONFIDENCE: ABOVE AVERAGE

AS MULTIPLE SHORTWAVE IMPULSES DIGGING ACROSS THE GREAT LAKES/OH
VALLEY AND NORTHEAST OVER THE NEXT COUPLE DAYS...A LONGWAVE TROUGH
MOVING INTO THE EASTERN U.S. WILL GRADUALLY SHIFT TOWARD THE EAST
COAST BY MON AND TUES...AND BEGIN TO THEN LIFT OUT ON WED. THE
MODELS ARE IN GOOD AGREEMENT WITH THEIR MASS FIELD DETAILS THROUGH
TUES...BUT BY WED...THE 12Z NAM NOW APPEARS TO BE A BIT TOO SLOW
TO ADVANCE ITS TROUGH AXIS THROUGH THE NORTHEAST WHICH APPEARS
RELATED TO A DEEPER SHORTWAVE DROPPING SOUTHEAST FROM SOUTHERN
QUEBEC AND INTO THE BASE OF THE LARGER SCALE TROUGH. SO A GENERAL
MODEL COMPROMISE WILL BE PREFERRED HERE THROUGH 60 HOURS...WITH A
NON-NAM CONSENSUS THEREAFTER.


...UPPER LOW MOVING INTO BRITISH COLUMBIA BY MON...
...DAMPENING UPPER LOW APPROACHING NORTHERN CA/OR BY MON...
...LOW PRESSURE/COLD FRONT TRAVERSING THE NORTHERN U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 60 HOURS
            12Z UKMET/12Z CMC/12Z ECMWF BLEND...AFTER 60 HOURS
CONFIDENCE: AVERAGE

ALL OF THE MODELS INDICATE AN UPPER LOW EXITING THE GULF OF AK AND
MOVING INTO BRITISH COLUMBIA BY MON WITH A SOUTHWARD EXTENSION OF
A TROUGH AXIS IMPACTING THE PACIFIC NORTHWEST. BY TUES...THIS
ENERGY WILL MOVE EAST ACROSS ALBERTA AND OVER THE NORTHERN HIGH
PLAINS. MEANWHILE...A SEPARATE DAMPENING SHORTWAVE ADVANCING INTO
NORTHERN CA/OR ON MON WILL SHEAR QUICKLY DOWNSTREAM ACROSS THE
GREAT BASIN AND THEN WELL OUT ACROSS THE NORTHERN PLAINS/UPPER
MIDWEST TUES AND WED. BOTH THE ENERGY OVER SOUTHERN CANADA AND THE
SHEARING WAVE TO ITS SOUTH WILL WORK IN TANDEM TO DRIVE LOW
PRESSURE AND A FRONT ACROSS THE NORTHERN PLAINS AND TOWARD THE
UPPER MIDWEST THROUGH WED. IN FACT...MOST OF THE MODELS HAVE ONE
LOW CENTER IN VICINITY MN/WI ON WED...WITH ANOTHER LOW OVER THE
EITHER THE EASTERN MT HIGH PLAINS OR OVER SOUTHERN SASKATCHEWAN.
THE MODELS ARE IN GOOD AGREEMENT UNTIL ABOUT 60 HOURS WHEN THE 12Z
GFS BEGINS TO LAG THE MODEL CONSENSUS WITH BOTH PIECES OF ENERGY
AND BECOMES A SLOW OUTLIER. THE 12Z NAM APPEARS TOO FAR NORTH WITH
ITS LOW OVER MN BY THE END OF THE PERIOD. THIS LEAVES THE 12Z
UKMET/12Z CMC AND 12Z ECMWF WHICH CLUSTER TOGETHER REASONABLY WELL
WITH THIS LATEST CYCLE. THUS WILL PREFER A GENERAL MODEL
COMPROMISE THROUGH 60 HOURS...AND A BLEND OF THE NON-NCEP GUIDANCE
THEREAFTER.


...MID-LEVEL WEAKNESS ACROSS THE WESTERN GULF OF MEXICO...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-ECMWF CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS MAINTAIN A RELATIVELY BROAD MID LEVEL WEAKNESS OVER THE
WESTERN GULF OF MEXICO THROUGH THE PERIOD WITH SOME NORTHWARD
EXTENSION OF THIS UP ACROSS THE WESTERN GULF COAST REGION. THERE
IS RATHER GOOD MASS FIELD AGREEMENT WITH THE DETERMINISTIC
GUIDANCE ON THE LARGER SCALE WITH THIS...WITH EXCEPTION TO THE 12Z
ECMWF WHICH HAS A MORE NOTABLE WESTWARD RETROGRESSION OF THE
WEAKNESS INTO SOUTH TX AND NORTHEAST MX. THE 00Z ECENS MEAN WAS
ALSO ATTEMPTING TO DO THIS SOMEWHAT. WILL LEAN TOWARD A NON-ECMWF
CONSENSUS AND THUS LESS RETROGRESSION OF THIS ENERGY FOR THE TIME
BEING.

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

ORRISON

$$




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