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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1822Z Sep 13, 2014)
 
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Abbreviations and acronyms used in this product
 
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
222 PM EDT SAT SEP 13 2014

VALID 12Z WED SEP 17 2014 - 12Z SUN SEP 21 2014

THE 13/00Z GEFS-ECENS MEANS WERE IN GOOD AGREEMENT AND MAINTAINED
VERY GOOD CONTINUITY WITH THE MODERATELY-INTENSE AND BROAD CYCLONE
IN THE NORTHWEST GULF OF ALASKA BY MID PERIOD. THE 13/00Z
DETERMINISTIC RUNS CONTINUE TO DISPLAY RUN-TO-RUN VARIABILITY WITH
THE SMALLER-SCALE DETAILS---MAINLY WITH INTENSITY AND TIMING---AS
THE SECONDARY SHORTWAVES FORM AND ROTATE COUNTERCLOCKWISE THROUGH
THE BASE OF THE UPPER-LEVEL TROUGH AND INTO THE SOUTHERN COAST AND
PANHANDLE.

A SIDE NOTE TO THE VARIABILITY---THE 13/00Z DETERMINISTIC ECMWF
RUN WAS ALMOST A FULL DAY QUICKER WITH THE TRANSFER OF ENERGY FROM
THE BERING SEA TO THE GULF OF ALASKA (CENTERED AROUND THE 19/12Z
TIME FRAME) VERSUS THE DETERMINISTIC 13/00Z GFS.

FOR DAYS 7-8...THE CURRENT PACKAGE DOES TREND TO A GRADUAL
WEAKENING OF THE BROAD CYCLONIC FLOW IN THE GULF OF ALASKA---WITH
UNDERCUTTING ENERGY DIVING SOUTHEASTWARD STRIPPING AWAY THE COLD
POOL ALOFT AND SPREADING THE AIRMASS DOWNSTREAM INTO THE WEST
COAST OF THE MAINLAND.

VOJTESAK