8B.6
Trapped-fetch waves in a transitioning tropical cyclone (part I�the need and the theory)
Allan W. MacAfee, Canadian Hurricane Centre, Dartmouth, NS, Canada; and P. J. Bowyer
Forecast centres responsible for ocean wave prediction during tropical cyclone events are often left with unsatisfactory numerical guidance from wave models because of the models� strong dependence on atmospheric wind models. The problem of predicting maximum significant wave heights with a tropical cyclone becomes critical to the right of the storm�s track where the potential exists for a considerably enhanced fetch. This phenomenon is illustrated in the companion poster presentation on Hurricane Luis.
Using established wave theory, a quick and reliable estimation of maximum significant wave heights can be determined from only three variables: wind speed (the component in the direction of the system�s motion); system speed; and the fetch length within the storm. A simple nomogram�-for predicting maximum significant wave heights�-developed for Canadian Hurricane Centre (CHC) meteorologists, will be presented, highlighting the sensitivity between system speed and fetch enhancement / reduction. The nomogram is tested against the wave reports from Gert (1999); Bonnie (1998); Danielle (1998); Felix (1995); and Luis (1995).
The nomogram is converted to a computer algorithm which has been coupled with the CHC�s analytical wind model. Both models are part of HURR, the CHC operational meteorologists� TC analysis and prediction software tool. In the companion poster session, details of the model and case studies will be presented.
Note: HURR was presented at the 22nd Conference in Fort Collins and the analytical wind model was presented at the 23rd Conference in Dallas.
Session 8B, Extratropical transition I (Parallel with Sessions 8A and J5)
Thursday, 25 May 2000, 8:00 AM-9:45 AM
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