Assessment of hurricane observational under-sampling and its impact on estimated intensity

Periodically issuing estimates of hurricane intensity is an operational requirement for the National Hurricane Center. Because a hurricane's intensity is defined by the maximum near-surface one-minute average wind speed anywhere in the storm, observing this quantity is of paramount importance. However, observing platform limitations, both spatial and temporal, make measuring the peak wind generally difficult, if not impossible. Using a high-resolution (1.3 km) numerical simulation of Hurricane Isabel (2003), a series of simulated observing system experiments are performed to quantify the under-sampling of maximum observed winds relative to the actual (model-produced) peak. We test a number of current aircraft- based observing platforms, including in situ (GPS dropwindsonde, aircraft flight-level data) and remote sensing (SFMR). Finally, preliminary intensity estimates using surface wind observations from a Hurricane Imaging Radiometer (HIRAD), which is to be flown on the NASA WB-57 for the 2010 Genesis and Rapid Intensification Process (GRIP) experiment, will be presented within the context of hurricane undersampling.