Understanding uncertainty and its impact on hurricane forecasts and warnings requires detailed knowledge of physical processes occurring across many scales. Lately, emphasis has been on studies of uncertainty in hurricane forecasts to changes in parameterizations, initial conditions, and/or boundary conditions using high-resolution numerical models. Yet, there is a lack of observational data that can be used for validation of the models at the meso- and convective scales on which the individual physical processes are occurring. The need for high temporal and spatial observations to aid validation of numerical simulations and to develop applications focused on reducing the cost of hurricane evacuations is particularly critical as the cyclone makes landfall.

In September 2003, two mobile C-band Doppler radars, the Shared Mobile Teaching and Research Radars (SMART-Rs) observed Hurricane Isabel as it made landfall on the North Carolina coast. The SMART-Rs provided volume samples every three minutes with spatial resolution less than one km. The analyses presented at this conference will show the relative importance of advection to evolution in local changes of the precipitation and wind fields as mesoscale rainbands made landfall. We will also document a feature that has not been noted in previous conceptual models of land-falling hurricanes— low-level mesoscale ascent through a radially-oriented connecting band that likely aided in the production of heavy rains and widespread flooding along the inland coast. Finally, we will discuss the variability of the primary asymmetric vortex circulation and convective eyewall intensity during the failed eyewall replacement cycle as the storm made landfall.

The SMART-R dual-Doppler analyses are a unique dataset that we hope will stimulate quantitative validation of numerical models and lead to better understanding of the variability and interaction of internal circulations of hurricanes during landfall. The ability to accurately forecast convective and mesoscale circulations is instrumental in improving damaging wind warnings and Quantitative Precipitation Forecasts (QPF) that may be used to better target evacuations.