Climate Watch
By Rick Thoman Alaska Climate Specialist Alaska Center for Climate Assessment and Policy International Arctic Research Center/University of Alaska Fairbanks
The return of the Iditarod to the Norton Sound coast this year brought another bout of race-impacting strong winds to parts of trail between White Mountain and Safely.
Between March 12 and 19, the average wind speed at the Johnson’s Camp weather station east of Solomon was 28 mph, compared to 15 mph at White Mountain and 12 mph at Nome Airport. Gusts hit up to 57 mph on March 17 around 8 pm and stayed in the high 40 to 50 mph range for days. Things calmed down around midnight, March 20.
Everyone who has ever traveled along the coast between Cape Nome and the Topkok Hills in the winter and spring is well aware of the frequent occurrence of high winds and severe blowing and drifting snow in this region, and the Nome Kennel Club’s Topkok shelter cabin has been a life saver for many travelers caught in a storm.
Why is this region so windy sometimes when nearby areas (say, Nome) are not windy, but at other times the Topkok area is not any windier than other areas along the southern Seward Peninsula coast? The answer lies in orientation of the Seward Peninsula mountain ranges and the rivers that cut through them influencing the way air moves between higher and lower pressure. When cold air moves onto the Seward Peninsula from the north or west, this causes atmospheric pressure to rise, and near the ground the air will (approximately) flow from high pressure toward lower pressure to the south, so a general north wind develops. At the same time, the mountains function as partial “dam”, deflecting the cold air as it moves southward. The wall of rock that characterizes the north face of the Kigluaik Mountains is especially effective in shunting cold air to the west toward Brevig Mission and Teller, and southeast, where the cold air then pours southeastward through the Pilgrim and Niukluk River valleys before fanning out. The same process occurs on the east side of the Darby mountains. Of course, the “dam” of the mountain is leaky, there are many smaller scale processes and interactions with the land that combine to yield the winds that occur at a particular place. The meteorological patterns and processes that produce these winds are well known and understood. What’s much more difficult to access is the extent and severity of blowing snow in the windy areas, which depend on the local conditions of the snow surface, including the strength of any wind or rain crust and can vary greatly over short distances and so much more difficult to forecast.