August 2012 Synoptic Summary
|Highest Temperature||83°F at Beaver in the northeastern Interior on the 14th|
|Lowest Temperature||16°F at Chisana in the eastern Alaska Range on the 29th|
|Highest Average||58.1°F at the Palmer Job Corps northeast of Anchorage|
|Lowest Average||39.0°F at Atigun Pass in the central Brooks Range|
|Most Precipitation||15.31 inches at the Red Dog mine in the western Brooks Range|
|Strongest wind||72 mph at Cape Lisburne, on the far western Arctic coast on the 15th|
As can be expected, August had more active weather than July. Gales blew somewhere in Alaskan waters on 24 days of the month. Three significant low pressure systems affected Alaska during August, arriving at ten day intervals, on July 5, 15 and 25. Quite consistently, these low pressure systems affected Northwest Alaska far more that the rest of the realm. The Northwest had a rough, disagreeable month indeed. In contrast, marine weather in the Gulf of Alaska was abnormally quiet.
Temperatures were a few degrees cooler than normal over nearly all of Alaska south of the Brooks Range. The prevalent southwesterly winds over the Arctic caused temperatures north of the Brooks Range to be well above normal, especially east of Prudhoe Bay. This pattern was nearly identical to July's. Rainfall was above normal over much of Alaska, though the southeastern Interior and the eastern north Gulf of Alaska coast had only half the normal rainfall for August.
In Northwest Alaska, rainfall was well above normal in the western Brooks Range, the Noatak River valley, the eastern Seward Peninsula and the far western Interior. This pattern was similar to July's. The big difference was in the upper Noatak River Valley, where rainfall was more than four times the normal value for August. The greatest amount of rainfall measured at any Alaska weather station in August was 15.31 inches at the Red Dog mine north of Kotzebue. This rainfall is well over half of the precipitation for an entire year at the Red Dog mine. This is remarkable since the greatest precipitation in Alaska in any month is almost always on the North Gulf Coast or in Southeast Alaska.
The first of the three significant low pressure systems in August moved from the far north Chukchi Sea on August 5 and strengthened to 965 millibars (28.50 inches) on August 6. West winds on the lower perimeter of this low blew over the Alaska Arctic coast from August 6 through 9. These westerly winds were an important factor restraining the significant northward retreat of ice at Point Barrow.
The second low pressure system moved northeastward from Chukotka, the eastern part of Siberia, on August 14 and 15, reaching a strength of 980 millibars (28.94 inches). The weather front ahead of the low stalled over the northwest Alaska coast from August 15 to 17.
This second low pressure system had the greatest impact of August in Alaska. Torrential rain fell over Northwest Alaska from August 13 to 19. The heavy rainfall in the Wulik River valley brought a crest on the Wulik River of 15.3 feet – more than 3 feet above any crest in more than 25 years of records – on August 16.
The town of Kivalina is situated on a barrier island. In this event, the extraordinary discharge out of both the Wulik and Kivalina Rivers brought up the water level in the lagoon on the east side of the barrier island. Gale force onshore winds on August 15 and 16 brought up sea level and heavy surf on the west shore of the island, causing significant beach erosion. The combination of these two factors resulted in significant coastal flooding in Kivalina on August 15 and 16.
Most of the problems at Kivalina came from the lagoon rather than the ocean. High water in the lagoon on the east side of town flooded the landfill and damaged the water intake pipe from the Wulik River. The summer discharge from the Wulik River provides the supply of fresh water for the entire year. The river carried a large sediment load due the high water, and the waste from the landfill contaminated the lagoon. Two weeks after the flooding, the school in Kivalina was still closed because there was a very limited supply of fresh water. In fact, the school was not expected to open until the first of October.
The third large low pressure system of August was a 975 millibar (28.79 inches) which moved northeastward through Chukotka on August 23 and struck the northwest coast on August 24. Strong west winds swept over Norton Sound and Kotzebue Sound that day. On August 25, significant coastal flooding and beach erosion occurred at Kotzebue. At the highest point of the sea level and surf, the windsock at the airport was under water. Local residents said that this was the worst coastal flooding there since 1989. In Norton Sound, there was high surf, but no coastal flooding. The configuration of the Norton Sound coast attenuates incoming waves from the west. The v-shaped Chukchi Sea coast offshore of Kotzebue amplifies waves brought in by strong west winds.
At sea, gale force winds blew over parts of Alaskan waters on 24 days of August. Sea ice continued to be a problem as August began. Some ice floes around Point Barrow were observed through the first week of August. Adding to the difficulty of the situation, low clouds and fog precluded aerial reconnaissance of the coastal waters around Barrow for several days.
On August 8, some ice floes were still observed 7 to 10 miles offshore from Barrow. However, the edge of the pack ice had pulled northward more than 50 miles from Barrow by August 7. Further retreat of the ice edge followed. On August 9, the edge of the Chukchi Sea ice pack was more than 50 miles north of Barrow. At the end of August, the Alaska sector of the Chukchi Sea was completely ice free up to 75 degrees north latitude – about 300 miles offshore.
In the Beaufort Sea, sea ice conditions were favorable. On August 1, the coast from Barter Island eastward to Cape Perry was ice-free. The edge of the pack ice was 200 miles north of the coast. By August 31, the entire Arctic coast of Alaska was completely free of ice. The only ice left in the Beaufort Sea was west of Sachs Harbor in the Canadian Arctic. The edge of the pack ice in the western Beaufort Sea was well over 600 miles north of the coast.
On August 25, sea ice covered only 30 percent of the entire Arctic Ocean, less than in any year since records began in 1979.
River conditions in south central and northwest Alaska were often unfavorable. High water on the Matanuska River, north of Anchorage, eroded river banks to the extent that some homes fell into the river. At the end of August, the Koyukuk River in the northern Interior was near bank full, but did not cause significant flooding.
The high water on rivers in Southcentral Alaska had mixed effects on the fishing season. The annual runs of king salmon were at near record low levels. However, silver salmon, red salmon, sockeye salmon and pink salmon runs were good to excellent in rivers when river levels had dropped, leading to slower flow and clearer water. Out in the Gulf of Alaska, halibut fishing was good.
In Southcentral and Interior Alaska, a surprising and significant increase of stinging insects occurred. Insect specialists ascribed this to the relatively mild temperatures and heavy snow pack of the winter in much of these areas. Both conditions shelter queen bees.
One result of the frequent rain on the Seward Peninsula was the sinking of land at the west end of the main runway at Nome. The runway was closed on August 23, and was not expected to be returned to service until° October 1. The secondary runway requires considerably better weather than the primary runway for safe landings.
On the night of August 6, four to five inches of snow fell in Atigun Pass, in the central Brooks Range. Another bout of snow brought two inches of new snow to Atigun Pass on August 26. Travel on the Dalton Highway was briefly slowed in these events.
Clearing skies and an influx of cool air aloft occurred over the eastern Interior on August 22. Significant frosts were reported on the early morning of August 23. Temperatures in the northeast Interior were in the 20s.
The wildfire season was slow for most of August. The largest total of lightning strikes in a day was on August 2, when only 74 strikes were recorded by the Alaska Lightning Detection System. No lightning was detected at all on 14 days of August.
A spell of warm and dry weather at mid month, accompanied by brisk winds during the third week of August caused a quick resumption of the Dry Creek fire, on the flats south of the Tanana River. Thick smoke intermittently floated into Fairbanks on August 18 through 22, prompting the issuance of air quality advisories on several days. Renewed rainfall starting on August 25 dramatically suppressed the burning.
Alaskan volcanoes remained quiet. Small eruptions of the Cleveland volcano, located in the eastern Aleutians, occurred on August 4 and 19. Several small earthquakes occurred on Little Sitkan Volcano, in the western Aleutians, on August 29 and 30. Four small earth tremors occurred in the eastern Aleutians and offshore the northern coast of the Gulf of Alaska. Three small earthquakes were felt in Fairbanks, Nenana, Denali Park and Anchorage. Clear skies and lengthening hours of darkness gave the Fairbanks area a fine view of the first aurora of the season on the early morning of August 6.