Research Aircraft and Wind Profiler Observations in Gastineau Channel during a Taku Wind Event

Abstract

The flow in Gastineau Channel near Juneau, Alaska, during the moderate Taku wind event of 18 October 2004 is examined using observations from the University of Wyoming?s King Air research aircraft, two wind profilers, and surface weather stations. These data sources reveal low-level winds directed down the central portion of Gastineau Channel, that is, gap flow. Farther down the channel, and above this gap flow, the winds were strongly cross channel in association with the downslope flow that characterizes Taku events. The transition region between these two flows included strong vertical wind shear and severe turbulence; measurements from the King Air indicate turbulent kinetic energy locally exceeding 50 m2 s?2. A high-resolution simulation of this case using the Naval Research Laboratory?s Coupled Ocean?Atmosphere Mesoscale Prediction System reproduced the observed character of the mean flow. This case illustrates the hazard to aviation posed by even a moderate Taku wind event and shows the value of a wind profiler for monitoring the vertical wind shear responsible for the hazard.