Prognostic Meteorological Discussion
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000
FXUS10 KWNH 160423
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1222 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 12Z CMC BECOMES A PROGRESSIVE OUTLIER AS THE ENERGY
CROSSES THE CANADIAN MARITIMES. WILL PREFER A NON-CMC CONSENSUS AS
A RESULT.


...LARGE SCALE TROUGH MOVING INTO THE WESTERN U.S. THROUGH WED...
...MULTIPLE SHORTWAVE IMPULSES TRAVERSING THE WEST AND PLAINS...
...SURFACE LOW/COLD FRONT EJECTING OUT ACROSS PLAINS/MIDWEST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 12Z 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 12Z UKMET AND 12Z
CMC BOTH TEND TO TRACK THEIR SURFACE LOWS A BIT NORTH OF THE MODEL
CONSENSUS THROUGH DAY 1...WITH THE 00Z NAM/00Z GFS AND 12Z ECMWF
ALL A BIT FARTHER SOUTH. AS THE LOW TRACKS TOWARD THE GREAT LAKES
REGION...THE UKMET AND ESPECIALLY THE CMC ARE SOUTH OF THE MODEL
CONSENSUS. THE CMC ALSO BECOMES A WEAKER OUTLIER. MUCH BETTER
MODEL CLUSTERING RESIDES WITH THE GFS AND ECMWF. REGARDING A
SECOND SHORTWAVE CROSSING THE NORTHERN ROCKIES AND NORTHERN HIGH
PLAINS BY THURS...THERE IS EVEN BETTER MASS FIELD
AGREEMENT...ALTHOUGH THE CMC APPEARS TO BE A BIT TOO WEAK. 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...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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. 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 12Z 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. THE 00Z NAM AND 00Z GFS ARE THE MOST
PROGRESSIVE SOLUTIONS...WITH THE 00Z UKMET/00Z CMC AND 00Z ECMWF
ALL SLOWER. 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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