EXTREME SURFACE WINDS IN MIDLATITUDE STORMS - FORECASTING AND CHANGES IN CLIMATOLOGY

The meteorological conditions for high wind speeds and gusts are reviewed; it is pointed out that whereas wind engineers focus their attention on shear-generated turbulent flows produced in the presence of high synoptic pressure gradients, meteorological forecasters for mid-latitude climates are equally concerned with the production of gusts by the combined action of the boundary layer dynamics and thermal convection above it. Radar data, radiosonde observations and mean wind and gust measurements largely confirm the working hypotheses of forecasters. The theoretical analysis for how the upper level convective downdrafts interact with the boundary layer is developed in Section 3. The forecasting of extreme winds and other weather variables using ensemble techniques is now statistically significant for periods of up to 15 days ahead; recent results are reviewed in Section 4. Finally, in Section 5, using the results of different Global Climate Models, the effects of climate change on the frequency, intensity and tracks of storms and hurricanes are considered, in order to estimate how climate change might affect extreme surface winds.