Marine Thunderstorm Wind · Gulf of Alaska

Marine Exchange of Alaska station at Marmion Island measured a peak gust of 33.6kt at 115pm Tuesday with a sudden wind shift to the south, the same time that the first lightning strikes were detected nearby. As the cell tracked northward the gusts and the wind shift tracked with it. The Juneau airport measured a peak gust of 39kt at 150pm and the ferry M/V Kennicott measured a peak gust of 38kt at 238pm while transiting Favorite Channel.

Large sunny breaks opened up over the northern inner channels of SE Alaska mid morning on June 4th. To the north and to the south there were frontal bands passing overhead due to low pressure in the Gulf of Alaska. Light northerly winds were observed ahead of a frontal band, then the sunny breaks allowed for larger build-ups to form quickly as the band tracked northward across Chichagof and Admiralty Islands. The first lightning strikes were detected on Chichagof Island, west of Hoonah, at around 1245pm AKDT. This thunderstorm cell then tracked northward across Icy Strait and into Gustavus and Glacier Bay. Another thunderstorm cell saw it's first strikes at the NE corner Admiralty Island near Taku Inlet at about 115pm. This storm then tracked northward across the Juneau area, then through Favorite Channel and Southern Lynn Canal. The storm weakened as it progressed northward with the last lightning strikes detected in Berners Bay at about 315pm. The southerly wind shift with this frontal band produced peak gusts of 20 to 40 knots and distinct shelf clouds observed by webcams and spotters.