Alaska Statewide Summary
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Alaska Statewide Summary
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| October 2009 | | ||||||||||||||||||
| Weak low pressure aloft covered the mainland of Alaska on the first 5 days of October, strengthening on the 5th. This pattern shifted to the west on the 6th as a persistent Aleutian low developed and high pressure built over the mainland. The high pressure over the Alaskan mainland held until mid October, and brought mild, sunny fall weather to much of the area. During the third week of the month, circulation weakened as low pressure spread over the mainland. On the 27th high pressure was building over the Aleutians and low pressure strengthened significantly over the far western Bering Sea and more importantly, over the Gulf of Alaska. High pressure then built over the mainland of Alaska and skies cleared. Winds around the strengthened Gulf of Alaska low were vigorous. On the 24th and 25th, high winds at Ketchikan badly damaged some buildings. From the 29th through the 31st, strong northerly winds out of Cook Inlet and the lower Copper River lofted large quantities of dust, reddening the skies there. The 100 mile dust plumes were easily discernible on imagery from the MODIS satellite far above. The winds on the 29th caused some damage to buildings north of Anchorage. Circulation around Gulf of Alaska lows brought much rainfall to Kodiak Island during the month. The Kodiak weather station recorded 16.22” of rain, not far from the October record of 17.13”. A large portion of this, 6.40”, fell on the 9th. For much of October, Kodiak had flooding, landslides, erosion and washouts on some sections of roads. The persistent high pressure aloft over the mainland was a major factor in the extensive above normal temperatures which prevailed over virtually the entire mainland. Temperatures in the Arctic were above normal for yet another month. The average temperature for the month at Barrow was 24.9°F, the 4th warmest October in nearly 100 years of records there. This fit into a pattern of gradually rising October temperatures in Barrow, a trend that began in the mid 1980's. The 3 days of measurable snowfall at Fairbanks were the fewest such October days since the very light snowfall of October, 1969. McGrath had a high temperature of 67°F on the 10th; this set a new all-time high temperature mark for October in McGrath, in 68 years of continuous weather records. Some people in Fairbanks were playing golf into the second week of the month. The first half of October in the central Interior was sufficiently warm and dry for several wild land burns to be conducted. |
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| On the evening of the 10th, the Alaska Lightning Detection System picked up 8 strikes around Norton Sound. One of these lightning strikes turned out to be from a thunderstorm which reached Nome an hour after sunset on the 10th. In nearly a century of weather records, this was the first October thunderstorm at Nome. Touches of winter began arriving over Interior highlands during the second week of the month. Extensive snowfall and strong winds came to areas above the tree line with increasing frequency as the month progressed. A general trend toward colder temperatures over the mainland began in the third week of October. Aside from the flooding on Kodiak Island, Alaskan rivers flowed at low stages during October. At month's end, river ice in the central Interior typically ranged from 2 to 10 inches thick, and lake ice from 4 to 8 inches in thickness. This was considerably less than the ice at the end of October of the year before, but enough for some of the first forays out for ice fishing. There was a brief, small eruption of the Mount Cleveland volcano on the 2nd. Mount Redoubt, in lower Cook Inlet, which had been quite active earlier in the year, was quiet through October. Three earthquakes of magnitudes from 5.3 to 6.3 were recorded in the eastern Aleutians on the 12th, 13th and the 14th. No damage or injuries resulted. Aurora was observed above the Interior on the 26th. At sea, gales blew somewhere over Alaskan waters on 27 days of the month. The strongest storm of the month occurred on the 22nd as a 962 millibar (28.41”) low moved up to Kodiak Island. This weather system interacted with a strong 1034 millibar (30.53”) high about 400 miles north of Alaska's Arctic shoreline, and brought whole easterly gales to the Arctic coast. This low pressure system moved just northeast of Kodiak Island and strengthened to 961 millibars (28.38”) on the 23rd. Widespread gales continued over the area. On the perimeter of the low, Chinook winds off the Alaska Range brought temperatures at some Interior stations up to 50°F. Sea ice along the Alaskan Arctic coast was near normal in extent east of Barrow as October began. The corridor of open water from Barrow to Mackenzie Bay was closed by the end of the third week of the month. Pack ice cover in the east Chukchi Sea was less than normal for much of October. Toward the end of the month, the southern edge of the ice reached Point Hope, close to its average position. Kotzebue Sound was not frozen over until the 31st. In comparison, in 2008, the Sound was frozen over by the 9th - three weeks earlier. Some shore fast ice formed briefly on the Yukon River delta near the end of the month. Sea surface temperatures were near normal in the eastern Gulf of Alaska and 1 to 3°F below normal in the west. In the Bering Sea, surface water temperatures were near normal, although waters around Nunivak Island were 2 to 4°F warmer than normal. In the Arctic, the sea surface waters were from 2 to 5°F above normal west of Barrow and near normal to 2°F above normal in the east. |
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