Prognostic Meteorological Discussion
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000
FXAK02 KWNH 211849
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 PM EST SUN DEC 21 2014

VALID 12Z THU DEC 25 2014 - 12Z MON DEC 29 2014


A STORMY MEDIUM RANGE IS STILL PROMISED BY THE GLOBAL NUMERICAL
MODELS FOR THE ALEUTIANS AND BERING SEA. WITH TIME, THE ENSEMBLE
MEANS SHOW A GRADUAL RISE IN HEIGHTS ACROSS THE GULF OF ALASKA AND
THE EASTERNMOST BERING SEA, SIGNALLING A PATTERN CHANGE TOWARD THE
END OF THE MONTH. THE GUIDANCE AT WEEK 2 IS DOMINATED BY SOLUTIONS
THAT INDICATE A NEGATIVE ARCTIC OSCILLATION, WHICH INVARIABLY
MEANS THE BUILDING OF AN UPPER RIDGE OVER THE YUKON AND ALASKAN
INTERIOR. THE EUROPEAN CENTRE GUIDANCE HAS PROVEN FAR STEADIER
THAN THE GFS SOLUTIONS FOR THE PERIOD JUST PRIOR TO THE PATTERN
CHANGE--ESSENTIALLY THE CURRENT MEDIUM RANGE. HAVE ATTEMPTED TO
SALVAGE WHAT IS USABLE FROM THE VARIOUS OPERATIONAL RUNS OF THE
ECMWF, MOSTLY TO GIVE THE CYCLONIC GRADIENTS MORE OOMPH THAN THE
WASHED OUT ENSEMBLE MEANS. IN THE CASE OF THE 00Z/21 ECMWF, FOUND
THAT IT WAS SERVICEABLE WHEN BLENDED EVENLY WITH THE ECENS MEAN
FROM THE SAME DATA CYCLE THROUGH ABOUT 168 HOURS--AFTER WHICH IT
SENDS SIGNIFICANTLY MORE HEIGHT FALLS ACROSS THE GULF THAN THE
MEAN.


CISCO

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