Prognostic Meteorological Discussion
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FXAK02 KWNH 021839
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 PM EDT WED SEP 02 2015

VALID 12Z SUN SEP 06 2015 - 12Z THU SEP 10 2015

...EXTRATROPICAL LOW ASSOCIATED WITH CURRENT TROPICAL STORM
IGNACIO MAY THREATEN THE GULF OF AK/SE AK NEXT WEEK WITH HIGH
WIND/WAVES/PCPN...

...MODEL AND UNCERTAINTY ASSESSMENT AND OVERALL PATTERN/WEATHER
THREATS...

MANY OF THE DETERMINISTIC MODELS CONTINUE TO OFFER ABOVE AVERAGE
FORECAST SPREAD AND POOR RUN-RUN CONTINUITY AT MEDIUM RANGE TIME
SCALES. THE LAST COUPLE ECMWF RUNS HOWEVER HAVE BEEN OFFERING
IMPROVING RUN-RUN CONSISTENCY. THE 00 UTC ECMWF RUN ALSO SEEMS TO
BE A BEST MATCH WITH THE LATEST 5 DAY FORECAST OF CURRENT TROPICAL
STORM IGNACIO. IGNACIO IS NOW FORECAST BY THE CENTRAL PACIFIC
HURRICANE CENTER TO TRACK NORTHWARD OVER THE CENTRAL PACIFIC AND
CONTINUE TRANSITION INTO A POTENT EXTRATROPICAL LOW THAT THREATENS
THE GULF OF AK THEN SERN AK DAYS 5-8. THIS SOLUTION IS SHIFTED
MORE NEWD THAN YESTERDAY BASED ON MODEL TRENDS...BUT REMAINS
UNCERTAIN.

OTHERWISE...THE ALASKA MEDIUM RANGE PERIOD STILL OFFERS A BERING
SEA/AK PENINSULA TO GULF OF ALASKA STORM TRACK...CLIPPING THE
ALASKAN SRN TIER. A SERIES OF HARD TO TIME/JUDGE SYSTEMS IN THIS
FLOW WOULD LOCALLY ENHANCE PCPN/WEATHER POTENTIAL...ALBEIT WITH
BELOW NORMAL PREDICTABILITY. THE LAST SEVERAL DAYS OF GFS RUNS
HAVE OVERALL ALSO OFFERRED QUITE A BIT OF QUESTIONABLE STREAM FLOW
PHASING NEXT WEEK DOWN THROUGH NW/WRN AK INTO THE ERN BERING SEA.
PHASING IN THIS CHAOTIC PATTERN IS NOT VERY PREDICTABLE AT THESE
TIME FRAMES.

CONSIDERING THE THREAT FROM IGNACIO...LINGERING UNCERTAINTY AND AS
PER WFO COORDINATION...PREFER A SOLUTION CLOSEST TO THE 00 UTC
ECMWF BUT BLENDED WITH SOME 00 UTC NAEFS/ECMWF ENSEMBLE MEANS.

SCHICHTEL



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