Storm Warning 139, NWS Anchorage, AK

000 
FZAK61 PAFC 152312
OFFAER

OFFSHORE WATERS FORECAST
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT TUE SEP 15 2009

OFFSHORE WATERS FORECAST FOR THE GULF OF ALASKA WEST OF 144W

WIND FORECASTS REFLECT THE PREDOMINANT SPEED AND DIRECTION
EXPECTED. SEA FORECASTS REPRESENT AN AVERAGE OF THE HIGHEST
ONE-THIRD OF THE COMBINED WIND WAVE AND SWELL HEIGHT.

PKZ399-161400-
400 PM AKDT TUE SEP 15 2009
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 986 MB LOW NEAR 53N 144W WILL STRENGTHEN TO 976 MB AS IT MOVES 
TO 55N 149W WED AFTERNOON. THIS LOW WILL THEN WEAKEN TO 983 MB 
AS IT MOVES TO NEAR 57N 154W THU AFTERNOON.

$$

PKZ351-161400-
GULF OF ALASKA OFFSHORE NORTH OF 57N AND WEST OF 144W
400 PM AKDT TUE SEP 15 2009

...GALE WARNING THROUGH WEDNESDAY NIGHT...

.TONIGHT...NE WIND 45 KT BECOMING SE 35 KT AFTER MIDNIGHT. SEAS
15 FT. RAIN.
.WED...E WIND 30 TO 40 KT. SEAS 14 TO 19 FT. RAIN.
.WED NIGHT...SE WIND 40 KT. SEAS 19 FT. RAIN.
.THU...SE WIND 35 KT. SEAS 17 FT. 
.THU NIGHT...SE WIND 20 KT. SEAS 12 FT. 
.FRI AND SAT...S WIND 20 KT. SEAS 9 FT. 
.SUN...E WIND 25 KT. SEAS 10 FT.  

$$

PKZ352-161400-
GULF OF ALASKA OFFSHORE SOUTH OF 57N NORTH OF 55N AND WEST OF
144W
400 PM AKDT TUE SEP 15 2009

...GALE WARNING THROUGH WEDNESDAY NIGHT...

.TONIGHT...N TO E WIND 35 TO 45 KT. SEAS 13 TO 16 FT. RAIN.
.WED...E WIND 45 KT. SEAS 19 FT. RAIN.
.WED NIGHT...S WIND 40 KT. SEAS 18 FT. 
.THU...S WIND 30 KT. SEAS 14 FT. 
.THU NIGHT THROUGH SAT...SW WIND 20 KT. SEAS 10 FT. 
.SUN...NE WIND 25 KT. SEAS 12 FT.  

$$

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
140 PM AKDT MON SEP 14 2009

.ANALYSIS AND UPPER LEVELS...A LARGE CLOSED LOW NEAR 47N 150W
CONTINUES TO DIG EAST SOUTHEASTWARD CAUSING AMPLIFICATION OF THE
DOWNSTREAM RIDGE...WHICH IS BUILDING BACK OVER TOP OF THE CLOSED
LOW INTO MAINLAND ALASKA. THERE ARE MULTIPLE SHORT-WAVES EMBEDDED
WITHIN THE CIRCULATION AROUND THE UPPER CENTER...MAINLY ON THE
EAST TO NORTH SIDE...ROTATING NORTHWARD TOWARD THE GULF AND THEN
ROTATING NORTHWESTWARD ACROSS THE GULF. ONE SUCH WAVE IS MOVING
FROM THE WESTERN GULF INTO BRISTOL BAY THIS MORNING. THE RIDGING
TO THE NORTH IS MAINTAINING MOSTLY SUNNY SKIES OVER THE INTERIOR.

ANOTHER UPPER TROUGH OVER THE FAR WESTERN BERING IS DRIVING A
GALE FORCE SURFACE LOW EASTWARD ALONG THE WESTERN ALEUTIANS.
THE SUBTROPICAL JET IS NEAR ZONAL JUST SOUTH OF THE ALEUTIANS
AND THEN DROPS SOUTHEASTWARD AND AROUND THE UPPER LOW...AND THIS
SYSTEM WILL TAKE A SIMILAR TRACK.

.MODEL DISCUSSION...MODELS INITIALIZED WELL BUT THEN QUICKLY
DIVERGE ON LOW TRACK. WITH THE ALEUTIAN LOW THE DIFFERENCES ARE
PRIMARILY IN SPEED OF THE LOW. IN THE EAST THERE ARE POSITIONAL
DIFFERENCES AS THE LOW MOVES TO KODIAK ISLAND ON WEDNESDAY. IN
BOTH CASES THE GFS SOLUTION IS A NICE MIDDLE GROUND BETWEEN THE
OTHER SOLUTIONS AND MATCHES UP WELL WITH THE GFS ENSEMBLE MEAN.
THUS...NEW FORECAST WILL BE BASED OFF THE GFS MODEL.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AS THE UPPER SHORT-WAVE CONTINUES TO ROTATE
WESTWARD TONIGHT COASTAL SOUTHCENTRAL WILL CLEAR OUT FROM EAST TO
WEST. MEANWHILE...THE UPPER LOW/TROUGH WILL BOTTOM OUT AND THEN
BEGIN TO LIFT NORTHWARD TOWARD THE GULF AS AMPLIFYING DOWNSTREAM
RIDGE CAUSES ACCELERATION OF SOUTHERLY JET BETWEEN THE LOW AND RIDGE.

ALL MODEL SOLUTIONS POINT TO A SHORT-WAVE EXITING THE BOTTOM OF
THE TROUGH AND STRENGTHENING AND BECOMING THE PRIMARY LOW CENTER
AS IT MOVES INTO THE GULF TUESDAY NIGHT. A BREAK AHEAD OF THIS
SYSTEM WILL RESULT IN CLEAR SKIES ACROSS MOST OF SOUTHCENTRAL ON
TUESDAY. RAIN AND GALES WILL MOVE INTO THE GULF TUESDAY NIGHT AND
WILL MOSTLY HANG UP ALONG THE COAST WEDNESDAY AS STRONG EASTERLIES
PRODUCE DOWNSLOPE CONDITIONS TO LIMIT PRECIPITATION ON THE LEE SIDE
OF THE KENAI AND CHUGACH MOUNTAINS. THERE IS SOME UNCERTAINTY IN THE
TRACK OF THE LOW AS IT MOVES TO NEAR KODIAK ISLAND WEDNESDAY...BUT
THIS WILL MAINLY AFFECT WIND DIRECTIONS NEAR KODIAK. THIS STORM
SYSTEM WILL CONTINUE TO ROTATE WESTWARD AS THE ALEUTIAN SYSTEM
ROTATES UNDERNEATH IT. PRECIPITATION WILL CONTINUE MAINLY ALONG
THE COAST UNDER BROAD SOUTHEAST FLOW...ALTHOUGH AS EMBEDDED
SHORT0-WAVES CROSS SOUTHCENTRAL THERE MAY BE A FEW SHOWERS INLAND
AS WELL.

SOUTHWEST ALASKA...RAIN OR SHOWERS ASSOCIATED WITH THE UPPER
SHORT-WAVE WILL CONTINUE TO MOVE WESTWARD ACROSS BRISTOL BAY
TONIGHT...WITH JUST A FEW SHOWERS ON THE NORTHERN FRINGE OF
THIS FROM THE KUSKOKWIM VALLEY TO KUSKOKWIM DELTA. THERE WILL
THEN BE A BREAK TUESDAY BEFORE A GULF LOW BRINGS MORE RAIN/SHOWERS
BACK IN LATE TUESDAY NIGHT INTO WEDNESDAY. THE LOW WILL ACTUALLY
TRACK TO THE VICINITY OF BRISTOL BAY WEDNESDAY BY THURSDAY...SO
SHOWERY REGIME WILL PERSIST INTO THE END OF THE WEEK.

BERING SEA/ALEUTIANS...THE ALEUTIAN LOW WILL BEGIN TO TAKE MORE
OF A SOUTHEASTWARD TRACK LATE TUESDAY AS THE NORTHEAST PACIFIC
LOW BEGINS TO LIFT NORTHWARD TOWARD THE GULF AND THE LOWS BECOME
CLOSE ENOUGH TO BEGIN TO FUJIWARA AROUND EACH OTHER. AS THE LOW
EXITS INTO THE NORTH PACIFIC WEDNESDAY BROAD NORTHERLY FLOW WILL
ENSURE ACROSS THE BERING SEA REGION AND PERSIST THROUGH WEEKS
END AS A RIDGE SETS UP UPSTREAM.

.LONG TERM FORECAST...LONG-WAVE TROUGH WILL REMAIN CENTERED OVER
ALASKA AND THE NORTHEAST PACIFIC THROUGH NEXT WEEKEND WHILE A
STRONG RIDGE OVER EASTERN SIBERIA AND THE WESTERN BERING BLOCKS
THE WESTERLIES FROM BRINGING ANY STORMS IN FROM ASIA OR THE WEST
PACIFIC. THEREFORE...CLOUDY AND/OR SHOWERY REGIME WILL PERSIST
FROM THE EASTERN BERING ACROSS THE SOUTHERN MAINLAND. CONFIDENCE
HEADING INTO NEXT WEEK AS MEDIUM RANGE MODELS INDICATE AN AMPLIFYING
PATTERN WHICH COULD BRING A DEEP LOW INTO THE GULF AND A TROPICAL
SYSTEM UP TOWARD THE ALEUTIANS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...176.
         GALE WARNING...120 130 132 172 175.
FIRE WEATHER...NONE.

SEB SEP 09