3.3
The challenge of forecasting severe downslope windstorms
John M. Brown, NOAA/Forecast Systems Lab, Boulder, CO
Although, to my knowledge, Fred Sanders never did any work on terrain-induced windstorms or their prediction, he did tell of some harrowing downslope winds in Greenland while he was serving in the military. More to the point, Fred was always on the alert for weather phenomena, usually mesoscale, that were poorly handled by operational forecasters, and was eager to give the forecasters a hand by looking into them in detail with the expectation that a closer examination would lead to improvements in operational procedures for predicting them. It is in this spirit that I offer this abstract.
Many locations to the lee of mountain ranges in the Western United States occasionally experience destructive windstorms. The mesoscale dynamical processes giving rise to these events are now fairly well understood, but forecasting them remains a vexing prediction problem in many areas. Operational numerical models are only just now beginning to hint at such small-scale detail, and that not reliably, requiring forecasters to venture into realms beyond simple examination of model output. The theory of this phenomenon, based as it is on gravity-wave dynamics and experiments with simplified numerical models applied to idealized flow configurations, can be forbidding to the unprepared, and is sometimes difficult to apply in the operational setting. In this context I will review some current approaches to this problem and future directions that appear fruitful.
Session 3, Forecasting (Room 617)
Monday, 12 January 2004, 1:30 PM-2:30 PM, Room 617
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