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FXUS10 KWNH 171828
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 PM EDT TUE OCT 17 2017

VALID OCT 17/1200 UTC THRU OCT 21/0000 UTC

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

12Z FINAL MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


...UPPER TROUGH DIGGING INTO THE PACIFIC NORTHWEST WEDNESDAY NIGHT
WITH ASSOCIATED ATMOSPHERIC RIVER EVENT...
...TROUGH/COLD FRONT REACHING THE PLAINS ON FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM / 12Z ECMWF BLEND
CONFIDENCE: ABOVE AVERAGE

DIFFERENCES IN THE GUIDANCE ARE MINOR UNTIL THE UPPER TROUGH AXIS
MOVES OVER THE INTERMOUNTAIN WEST ON FRI. ENSEMBLES HAVE BEEN
TRENDING SLIGHTLY FASTER WITH THE UPPER TROUGH AXIS VALID FRIDAY
EVENING BUT THE 12Z GFS IS AT THE FAR LEADING EDGE OF THE LATEST
ENSEMBLE GUIDANCE...AND IS CONSIDERED TOO FAST. ONLY MINOR
ADJUSTMEMNTS WERE SEEN IN THE 12Z ECWFM/UKMET/CMC FOR THIS
SYSTEM...WITH THE 12Z GFS REMAINING FASTER. UPSTREAM FLOW IS
AMPLIFYING SO FASTER SOLUTIONS LIKE THE GFS ARE LESS PREFERRED. A
SOLUTION TOWARD THE MIDDLE OF THE LATEST ENSEMBLE
GUIDANCE...REPRESENTED BY A 12Z NAM / 12Z ECMWF BLEND IS
RECOMMENDED HERE.


...SHORTWAVE MOVING QUICKLY ALONG THE U.S.-CANADA BORDER THROUGH
THU WITH ASSOCIATED DEEPENING SURFACE LOW AND COLD FRONT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENEARL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN BETTER AGREEMENT WITH THE 12Z UKMET A LITTLE
FASTER COMPARED TO ITS 00Z RUN AND IN BETTER ALIGNMENT WITH THE
REMAINING DETERMINISTIC GUIDANCE. THE ENSEMBLE MEANS SHOW GOOD
AGREEMENT WITH THE 12Z DETERMINISTIC CONSENSUS SO A GENERAL MODEL
BLEND IS RECOMMENDED.


...UPPER LEVEL TROUGH AXIS CROSSING THE SRN ROCKIES INTO THE
PLAINS ON FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

MINOR AMPLITUDE/TIMING DIFFERENCES EXIST WITH THIS SYSTEM...WITH A
12Z GFS AND 00Z ECMWF BLEND DOWN THE MIDDLE OF THESE DIFFERENCES.


...LINGERING BROAD TROUGH OVER THE SOUTHEAST STATES WITH SLOW
MOVING COLD FRONT IN THE VICINITY OF FLORIDA...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


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

OTTO

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