Monday, November 7, 2011

Alaska Megastorm Update I: Hurricane Force Winds Predicted

Image (click to enlarge): The latest (8:30 pm GMT, November 7) satellite image shows an intensifying storm moving away from northern Japan and east of the Kamchatka Peninsula as it approaches the Bering Sea, from SSEC, University of Wisconsin

3:30 PM AKST Update: The National Weather Service is calling for this to be "one of the most severe Bering Sea storms on record":
A RAPIDLY DEVELOPING STORM LOCATED ABOUT 600 MILES SOUTHWEST  
OF SHEMYA THIS AFTERNOON WILL INTENSIFY INTO ONE OF THE
MOST SEVERE BERING SEA STORMS ON RECORD AS IT MOVES NORTHWARD
ACROSS THE CHUKOTSK PENINSULA TUESDAY NIGHT. THIS STORM
HAS THE POTENTIAL TO PRODUCE WIDESPREAD DAMAGE.

THE STORM WILL PRODUCE WIDESPREAD WINDS OF 40 TO 55 MPH
WITH HIGHER GUSTS OVER THE WEST COAST TUESDAY NIGHT INTO
WEDNESDAY EVENING. STRONG WEST WINDS ARE EXPECTED TO CONTINUE
OVER ST LAWRENCE ISLAND WEDNESDAY NIGHT. GUSTS TO 70 MPH CAN BE
EXPECTED ALONG THE CHUKOTSK PENINSULA AND IN AREAS NEAR KOTZEBUE.
WINDS OF 60 TO 75 MPH ARE EXPECTED OVER ST LAWRENCE ISLAND AND
THE BERING STRAIT COAST. WINDS ARE EXPECTED TO APPROACH HURRICANE
FORCE OVER THE CHUKCHI SEA AND NORTHERN BERING SEA. THE STRONG
WINDS WILL GENERATE SEAS TO AS HIGH AS 20 FEET OVER THE CHUKCHI
SEA...AND TO 15 TO 25 FEET OVER THE NORTHERN BERING SEA.

THE STRONG WINDS WILL PUSH LARGE AMOUNTS OF WATER INTO NORTON
SOUND...RAISING SEA LEVELS TO AS HIGH AS 8 TO 9 FEET ABOVE NORMAL
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. THE HIGH SEA LEVELS
COMBINED WITH HIGH WAVES WILL PRODUCE SEVERE BEACH EROSION AND
MAJOR COASTAL FLOODING ALONG THE NORTHERN AND EASTERN SHORES OF
NORTON SOUND AND ALONG THE BERING STRAIT COAST. HIGH WATER
LEVELS WILL PRODUCE COASTAL FLOODING ALONG THE SOUTHERN
SHORE OF NORTON SOUND. STRONG WINDS AND WAVE ACTION MAY PUSH
ICE IN NORTON BAY ON SHORE.

MODERATELY ELEVATED SEA LEVELS AND HIGH WAVES WILL CAUSE
SEVERE BEACH EROSION AND MAJOR COASTAL FLOODING ALONG THE
SOUTH AND WEST FACING COASTS OF ST LAWRENCE ISLAND TUESDAY
THROUGH WEDNESDAY NIGHT.

ALONG THE CHUKCHI SEA COAST FROM CAPE KRUSENSTERN NORTHWEST...
SOUTHEAST WINDS GUSTING TO A HIGH AS 70 MPH WILL PRODUCE HIGH
WAVES AND SOME ELEVATION OF SEA LEVELS...RESULTING IN SEVERE
BEACH EROSION AND MAJOR COASTAL FLOODING. THE VILLAGE OF
KIVALINA WILL BE HIGHLY VULNERABLE TO DAMAGE CAUSED BY
BEACH EROSION AND COASTAL FLOODING.

THE STORM WILL ALSO PRODUCE SIGNIFICANT SNOWFALL AND BLIZZARD
CONDITIONS OVER ALMOST ALL OF THE WEST COAST TUESDAY NIGHT
AND WEDNESDAY. SNOWFALL AMOUNTS OF AS MUCH AS 14 INCHES
ARE EXPECTED ALONG THE SOUTHERN SEWARD PENINSULA COAST AND
IN PARTS OF THE INTERIOR SEWARD PENINSULA.

AGAIN...THIS IS AN EXTREMELY DANGEROUS AND LIFE THREATENING
STORM WHICH WILL BE ONE OF THE WORST ON RECORD OVER THE BERING
SEA AND THE WEST COAST.
Original Post:
This morning's forecast discussion from the National Weather Service notes that the storm developing in the northern Pacific has been well predicted so far by both the U.S. GFS model and the European model. The models have also been consistent from one run to the next. Winds are forecast to be locally as high as 75 mph along the Alaskan coast. Although the water level may not reach the record height of 1974, the potential for severe coastal damage is very high because of the lack of sea ice. From the NWS forecast discussion:
THE STRONGEST WINDS ARE EXPECTED TO BE SOUTH 75 MPH NEAR SAVOONGA  
AT THE HEIGHT OF THE STORM ON TUESDAY NIGHT. SAVOONGA IS A
SINGULAR POINT WITH STRONG SOUTH WINDS BECAUSE ATUK
MOUNTAIN...SUMMIT ELEVATION 2207 FEET...IS JUST SOUTH OF THE
VILLAGE.

THE STORM IN THE BERING SEA TUESDAY AND WEDNESDAY IS REMARKABLY
SIMILAR TO THE BERING SEA STORM OF NOVEMBER 11 AND 12 1974. THE
1974 STORM REMAINS THE MOST SEVERE AT NOME IN 113 YEARS OF
RECORDS THERE. THE CREST AT NOME WAS A 13.2 FOOT RISE IN STATIC
WATER LEVEL ABOVE MEAN SEA LEVEL. THE CREST THIS TUESDAY NIGHT
AND WEDNESDAY AT NOME IS EXPECTED TO BE 10 FEET.

DUE TO A STRONG SOUTHERLY INFLUX OF WARMER AIR OVER THE BERING SEA
COAST STARTING LATE TONIGHT...BLIZZARD CONDITIONS ARE NOT EXPECTED
AROUND THE ZONES OF THE YUKON DELTA AND NORTON SOUND COASTAL
ZONES. HENCE...WINTER STORM WARNINGS FOR HEAVY SNOW ARE IN EFFECT
FOR THOSE AREAS.

INDEED...THE SNOW ON SAINT LAWRENCE ISLAND WILL BE MIXED WITH
RAIN TUESDAY AND TUESDAY NIGHT. A HIGH WIND WARNING IS IN EFFECT
FOR SAINT LAWRENCE ISLAND AND THE BERING STRAIT COAST.
A Public Information Statement from Fairbanks says, in part:
ALL SOUTH AND WEST FACING COASTS ON THE BERING SEA FROM THE YUKON  
DELTA UP TO BERING STRAIT...AND THE CHUKCHI SEA COAST NORTH OF
KOTZEBUE UP TO POINT HOPE...ARE EXPECTED TO HAVE MAJOR COASTAL
FLOODING AND BEACH EROSION TUESDAY NIGHT AND WEDNESDAY. SOUTHERLY
WINDS FROM 40 TO 75 MPH ARE FORECAST TO DRIVE UP THE SEA FROM 4 TO
10 FEET ABOVE NORMAL LEVELS. THE STRONGEST WINDS AND COASTAL
FLOODING WILL SPREAD OVER THE NORTHERN BERING SEA TUESDAY NIGHT
AND THEN OVER THE CHUKCHI SEA COAST ON WEDNESDAY. THE STORM WILL
SUBSIDE THURSDAY.

NEARLY ALL OF THE ALASKAN NORTHWEST COAST REMAINS ICE FREE AS OF
TODAY...AND THIS WILL NOT CHANGE FOR SOME TIME. KOTZEBUE SOUND AND
NORTON BAY ARE ICE COVERED. LARGE STRETCHES OF NORTHWEST ALASKA
COASTLINE HAVE VIRTUALLY NO ICE COVER TO LESSEN THE IMPACT OF
INCOMING SURF. THIS WAS NOT SO IN THE 1974 STORM.

THIS IS A DANGEROUS STORM. ALTHOUGH IT MAY NOT TURN OUT TO BE AS
INTENSE AS THE 1974 STORM...IT HAS THE POTENTIAL TO CAUSE
WIDESPREAD DAMAGE.

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