Prognostic Meteorological Discussion
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000
FXUS10 KWNH 160637
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
235 AM EDT WED AUG 16 2017

VALID AUG 16/0000 UTC THRU AUG 19/1200 UTC

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

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

...SHORTWAVE ENERGY SHEARING ACROSS THE OH/TN VALLEYS ON WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT WITH THE WEAK SHORTWAVE/MCV THAT
WILL BE SHEARING OUT ACROSS THE OH/TN VALLEYS THROUGH WED. A
GENERAL MODEL COMPROMISE WILL BE PREFERRED.


...UPPER LOW OVER QUEBEC APPROACHING THE NORTHEAST BY WED...
...HEIGHT FALLS ADVANCING ACROSS THE CANADIAN MARITIMES BY THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE DIFFERENCE ARE RATHER MINOR WITH THE DETAILS OF THE STRONG
UPPER LOW THAT IS FORECAST TO DROP SOUTHEAST ACROSS QUEBEC AND
BRUSH THE NORTHEAST THROUGH WED. HOWEVER...AFTER ABOUT 36
HOURS...THE 00Z CMC BECOMES A PROGRESSIVE OUTLIER AS THE ENERGY
CROSSES THE CANADIAN MARITIMES. WILL PREFER A NON-CMC CONSENSUS AS
A RESULT.


...LARGE SCALE TROUGH CROSSING THE WESTERN U.S. THROUGH WED...
...MULTIPLE SHORTWAVE IMPULSES TRAVERSING THE WEST AND PLAINS...
...SURFACE LOW/COLD FRONT EJECTING ACROSS THE PLAINS/MIDWEST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS BRING A LARGER SCALE TROUGH THROUGH THE WEST AND ACROSS
THE PLAINS THROUGH WED ALONG WITH MULTIPLE SHORTWAVE IMPULSES THAT
WILL EJECT OUT OF THE WEST AND ACROSS THE CENTRAL/NORTHERN
PLAINS...UPPER MIDWEST AND GREAT LAKES REGION THROUGH FRI. THE
MODELS SHOW REASONABLY GOOD AGREEMENT ON THE LARGER SCALE WITH THE
TROUGH...HOWEVER THERE ARE SOME TIMING AND DEPTH DIFFERENCES OF
NOTE WITH THE EMBEDDED SHORTWAVES.

REGARDING THE FIRST SHORTWAVE WHICH IS CURRENTLY DIGGING ACROSS
THE GREAT BASIN...THE GUIDANCE ADVANCES THIS ENERGY ACROSS THE
CENTRAL/NORTHERN PLAINS AND UPPER MIDWEST THROUGH WED ALONG WITH A
SURFACE LOW AND ATTENDANT COLD FRONT THAT THEN TRAVERSES THE GREAT
LAKES REGION THURS AND FRI. THE 00Z NAM THROUGH THE DAY 1 PERIOD
APPEARS A BIT TOO DEEP WITH THIS TROUGH AND IS ALSO A LITTLE SLOW
WITH THE SURFACE LOW EVOLUTION. THEREAFTER...IT COMES INTO BETTER
AGREEMENT WITH THE MULTI-MODEL CONSENSUS. THE 00Z UKMET THOUGH IS
OVERALL A DEEPER OUTLIER WITH THE TROUGH ALOFT AND ALSO WITH THE
SURFACE LOW EVOLUTION THROUGH THE PERIOD. THE 00Z CMC HAS TRENDED
STRONGER WITH ITS SURFACE LOW AND IS CLOSER TO THE MODEL
CONSENSUS...BUT ITS SURFACE LOW TRACK STILL OCCASIONALLY APPEARS
TO BE TOO FAR SOUTH AS IT CROSSES THE GREAT LAKES REGION. THE 00Z
GFS AND 00Z ECMWF ARE BETTER CLUSTERED AT THIS POINT AND ARE
CLOSEST TO THE MODEL CONSENSUS. REGARDING A SECOND SHORTWAVE
CROSSING THE NORTHERN ROCKIES AND NORTHERN HIGH PLAINS BY
THURS...THERE IS VERY GOOD MASS FIELD AGREEMENT AT THIS POINT.
BASED ON ALL OF THIS...WILL PREFER A GFS/ECMWF BLEND FOR ALL OF
THE ENERGY.


...UPPER TROUGH SETTLING DOWN OVER THE SOUTHWEST U.S. WED/THURS...
...CLOSED MID LEVEL LOW OVER SOUTHERN CA BY FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS PINCH OFF SOME OF THE SHORTWAVE ENERGY ARRIVING OVER
THE WEST WITH THE MAIN UPPER TROUGH AND DROP IT GENERALLY SOUTH
ACROSS THE GREAT BASIN AND INTO THE SOUTHWEST U.S. BY WED AND
THURS. BY FRI...THE ENERGY EVOLVES INTO A CLOSED MID LEVEL LOW
OVER SOUTHERN CA. THE SPREAD IS VERY MINOR HERE...SO A GENERAL
MODEL COMPROMISE WILL BE PREFERRED.


...UPPER TROUGH ARRIVING ACROSS THE PACIFIC NORTHWEST BY FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS BRING A PROGRESSIVE UPPER TROUGH ACROSS THE GULF OF AK
AND INTO BRITISH COLUMBIA AND PORTIONS OF THE PACIFIC NORTHWEST BY
FRI. THE MODEL DIFFERENCES ARE RATHER MINOR THROUGH 72 HOURS...BUT
THEREAFTER THE 00Z NAM AND 00Z GFS ARE A TAD FASTER THAN THE
NON-NCEP GUIDANCE. WILL COMPROMISE BETWEEN THE CAMPS BY
RECOMMENDING A GFS/ECMWF BLEND AT THIS TIME.


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

ORRISON

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