Prognostic Meteorological Discussion
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000
FXUS10 KWNH 211853
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 PM EDT THU SEP 21 2017

VALID SEP 21/1200 UTC THRU SEP 25/0000 UTC

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

12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...WESTERN CONUS TROUGH AMPLIFICATION AND MOVEMENT THROUGH
SATURDAY...
...SURFACE LOW CYCLOGENESIS AND FRONTAL DEVELOPMENT OVER NORTHERN
PLAINS THROUGH SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/NAM/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOOD GENERAL AGREEMENT OF SETTING UP THE TROUGH ACROSS THE WEST
INTO SATURDAY. 12Z GUIDANCE IS IN FAIR AGREEMENT WITH MOTION AND
STRENGTH OF THE TROUGH/LOW SUNDAY. THE 12Z UKMET AND CMC BOTH
TRENDED SLOWER/MORE CLOSED BY 25/00Z WHICH IS IN LINE WITH THE
OTHER 12Z GUIDANCE. THE CMC IS STILL A BIT MORE PROGRESSIVE AND
DUE TO THE BLOCKING PATTERN A SLOWER EJECTION OF THE LOW IS
PREFERRED. THE 12Z UKMET AND CMC STILL HAVE STRONGER MID-LEVEL
ENERGY DOWNSTREAM OF THE LOW WHICH MAKES FOR GREATER SURFACE LOW
PRESSURE DEVELOPMENT OVER THE NORTHERN PLAINS THIS WEEKEND. WITH
AN EXPECTATION THAT THE ENERGY WILL BE CONTAINED MORE AROUND THE
LOW IN THE INTERMOUNTAIN WEST, WILL MAINTAIN A PREFERENCE OF THE
12Z GFS/NAM/ECMWF BLEND...WITH THE 12Z ECMWF MAKING ONLY MINOR
ADJUSTMENTS FROM ITS 00Z RUN.


...TROPICAL STORM JOSE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GUIDANCE CONSENSUS
CONFIDENCE: REFERENCE NHC PRODUCTS

ALL GUIDANCE IN GREAT AGREEMENT OF JOSE WEAKENING AND DRIFTING
BACK WEST NEARLY TO 70W THROUGH 23/00Z. ONLY SLIGHT TRACK
VARIATIONS IN THE GUIDANCE SUITE AS JOSE THEN DRIFTS EAST AS IT
FURTHER WEAKENS THROUGH 25/00Z. 12Z CMC/GFS ALSO WEAKEN THE SYSTEM
QUICKER. CONSENSUS OF MODELS IS CLOSEST TO 15Z NHC ADVISORY.


...WEAK UPPER LEVEL TROUGH OVER THE SOUTHEAST THROUGH SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE TROUGH OVER THE SOUTHEASTERN CONUS IS HANDLED SIMILARLY AMONG
THE GUIDANCE. THEREFORE A GENERAL MODEL CONSENSUS IS PREFERRED.


...HURRICANE MARIA...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: REFERENCE NHC PRODUCTS

GOOD AGREEMENT AMONG GUIDANCE COMPARED TO THE 15Z NHC ADVISORY
EXCEPT FOR THE 12Z NAM WHICH REMAINS EAST. THE 12Z CMC IS FARTHEST
WEST BY END OF PERIOD/SUNDAY EVENING. STILL PREFER A NON-NAM BLEND
WHICH IS CLOSEST TO NHC 15Z ADVISORY.

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

JACKSON

$$





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