Prognostic Meteorological Discussion
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FXUS10 KWNH 290429
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 AM EDT THU SEP 29 2016

VALID SEP 29/0000 UTC THRU OCT 02/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...DEVELOPING WEST COAST UPPER TROUGH/CLOSED LOW...
...LEAD SHORTWAVE EJECTING THROUGH THE INTERIOR...

PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF...MAIN UPPER
TROUGH/CLOSED LOW
            NON-GFS CONSENSUS....WITH THE LEAD SHORTWAVE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ALL OF THE MODELS SHOW A DEEP UPPER TROUGH AND ASSOCIATED CLOSE
LOW DIGGING SOUTHEAST AND TOWARD THE WEST COAST THROUGH THE
PERIOD...WITH A LEAD SHORTWAVE THAT IS EXPECTED TO DROP INITIALLY
SOUTH AND THEN EJECTING INLAND ACROSS THE INTERMOUNTAIN WEST. THE
00Z GFS APPEARS TO BE A RELATIVELY SLOW AND DEEP OUTLIER WITH THE
LEAD SHORTWAVE AS IT EJECTS INLAND AHEAD OF THE STRONGER HEIGHT
FALLS DROPPING SOUTH ALONG THE WEST COAST. THE REMAINING MODELS
ARE WELL CLUSTERED ON A SOMEWHAT WEAKER AND FASTER SOLUTION AS THE
ENERGY SHEARS OUT OVER THE INTERIOR. REGARDING THE DEEP UPPER
TROUGH/CLOSED LOW BY THE END OF THE PERIOD...THE 12Z UKMET APPEARS
TO FOCUS A BIT MORE ENERGY NORTH OF THE MODEL CONSENSUS. THE 00Z
NAM AND 00Z GFS ARE BOTH DROPPING THE ENERGY A TAD FARTHER
SOUTH...AND THE 12Z ECMWF SPLITS THE DIFFERENCE BETWEEN CAMPS.
WILL FAVOR A NON-GFS CONSENSUS WITH THE LEAD SHORTWAVE...BUT WILL
SUGGEST A GFS/ECMWF COMPROMISE WITH THE MAIN UPPER TROUGH/CLOSED
LOW JUST OFF THE WEST COAST BY THE END OF THE PERIOD.


...DEEP CYCLONE ACROSS MIDWEST DOUBLING BACK TOWARDS MI...

PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE IN VERY GOOD AGREEMENT WITH THEIR MASS FIELDS
THROUGH 48 HOURS WITH THE UPPER LOW OVER THE OH VALLEY.
THEREAFTER...ALL OF THE MODELS ALSO INDICATE THE UPPER LOW LIFTING
GRADUALLY BACK NORTH INTO MI WITH SOME MINOR TIMING DIFFERENCES.
THE 12Z UKMET WAS A BIT QUICKER TO LIFT THE SYSTEM BACK TO THE
NORTH...AND ENDS UP A BIT NORTH OF THE MODEL CONSENSUS. THERE IS
STILL SOME LONGITUDINAL DIFFERENCE IN THE PLACEMENT OF THE SYSTEM
ESPECIALLY BETWEEN 48 AND 72 HOURS...WITH THE 00Z GFS A BIT EAST
OF THE MODEL CONSENSUS AND THE 12Z ECMWF FARTHER WEST. ALTHOUGH
THE 00Z NAM IS FARTHEST WEST OVERALL DURING THIS TIME FRAME. THERE
IS A TREND TOWARD NARROWING THE SPREAD BETWEEN THE GFS AND
ECMWF...AND AT THIS TIME A BLEND OF THESE TWO SOLUTIONS WILL BE
PREFERRED.


...CLOSED LOW LIFTING OUT OF THE SOUTHWEST...
...SHORTWAVE LIFTING MOVING THROUGH ND FRIDAY...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE GENERALLY SHOWS GOOD AGREEMENT WITH THESE SYSTEMS.  A
GENERAL MODEL COMPROMISE WILL THEREFORE BE PREFERRED AT THIS TIME.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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