Monday, 28 April 2008: 11:15 AM
Palms GF (Wyndham Orlando Resort)
The Advanced Hurricane WRF (AHW) has been used for real-time prediction and retrospective research simulations of Atlantic basin tropical cyclones since 2003. Verification of the intensity and track errors of the AHW forecasts has shown that 12 km and 4 km simulations perform as well as, and occasionally superior to, the National Hurricane Center official forecasts and other operational forecast systems. Verification of the inner core structure of the simulated storms, examined with a finest mesh of 1.33 km, has proven less successful. Realistic eye, eyewall and inner spiral rainband structures are simulated, but the eye is generally too small and the eyewall convection too wide. Outside of the eyewall, the azimuthal location of convective bands and asymmetries in the wind field agree well with reconnaissance observations and concentric eyewall cycles are simulated on realistic time and spatial scales. Closer to the core, the eyewall potential vorticity maximum provided steep gradients on which copious vortex Rossby waves and mesovortices were noted to propagate in accord with theory. The amplitude of these asymmetries and their dominant wavenumbers however, are inconsistent with observations. Possible explanations for the high Rossby wave activity, the effects of these asymmetries on storm intensity and sensitivity experiments undertaken to reduce the spurious wave activity will be the focus of this presentation.
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