Large storm over the Arctic Ocean
Suomi NPP VIIRS 11.45 µm IR channel images (click image to play animation)
AWIPS images of Suomi NPP VIIRS 11.45 µm IR channel data (above; click image to play animation) showed a very large storm moving slowly across the Arctic Ocean during the 13 October – 15 October 2012 period. Large areas of stationary sea ice could be seen over portions of the Arctic Ocean.
Widespread convective elements were apparent on the IR images, which were a result of an unstable air mass due to cold air advection across the region — this deep layer of instability could be seen on the 15 October 00 UTC rawinsonde data plot from Barrow, Alaska (below).
Barrow, Alaska rawinsonde data (00 UTC 15 October)
The Area Forecast Discussion issued by the Fairbanks National Weather Service forecast office summarized the impacts of this large storm along the arctic coast of Alaska:
NORTHERN ALASKA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FAIRBANKS AK 501 AM AKDT MON OCT 15 2012 .DISCUSSION... THE GFS AND NAM COMPUTER WEATHER FORECAST MODELS ARE IN GOOD AGREEMENT THROUGH 4 AM WEDNESDAY. A LARGE AND LONG-LIVED LOW PRESSURE SYSTEM NOW ABOUT 600 MILES NORTHWEST OF BARROW IS GRADUALLY WEAKENING...AND DRIFTING SLOWLY TO THE NORTHWEST. THE WEATHER AT SEA IN THE CHUKCHI AND ALONG THE ALASKAN CHUKCHI SEA COAST IS THE MOST IMPORTANT ASPECT OF THIS MORNINGS FORECASTS. COLD AIR HAS BEEN STREAMING DOWN FROM THE FAR NORTHWESTERN CHUKCHI SEA THROUGH BERING STRAIT. THE EDGE OF THE ARCTIC ICE PACK IS NOW ABOUT 400 MILES NORTHWEST OF BARROW...AND ADVANCING SOUTHWARD 10 TO 15 MILES A DAY. THE ABNORMALLY LONG FETCH OVER THE CHUKCHI SEA DOWN TO THE ALASKA ARCTIC COAST WEST OF CAPE HALKETT IS THE MAIN FACTOR IN THE BUILDUP OF ROUGH SEAS. THE INCOMING SWELLS AT BARROW HAVE BEEN FROM 4 TO 6 FEET HIGH. DUE TO ABNORMALLY FREQUENT WEST WINDS IN THE ALASKAN ARCTIC THIS SUMMER AND FALL...THE WIDE BEACH AND SHALLOW WATER OUT FROM SHORE HAVE BEEN MUCH REDUCED. AS A RESULT...THE INCOMING SWELLS ON THE ALASKAN NORTHERN ARCTIC COAST ARE NOT BREAKING SEVERAL HUNDRED YARDS OFFSHORE AS THEY USUALLY DO. INSTEAD...THE INBOUND SWELLS ARE NOT BREAKING UNTIL REACHING THE SHORELINE. THE RUN UP OF THE BREAKING SURF IS CONSIDERABLY MORE NOW THAN IT WOULD BE UNDER NORMAL SHORELINE CONDITIONS. POLAR ORBITING SATELLITE IMAGERY HAS SHOWN EXTENSIVE CONVECTIVE CLOUDS OVER THE CHUKCHI SEA. THIS...AND THE EARLY MORNING WEATHER BALLOON DATA FROM BARROW...KOTZEBUE...AND NOME...INDICATE AN UNSTABLE AIR MASS. THIS FEATURE GIVES A LARGER TRANSFER OF ENERGY FROM THE WIND TO THE SEA. THIS HAS BEEN THE CASE FOR SEVERAL DAYS NOW.