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Aircraft

Tropical cyclones are ideal subjects for study from instrumented aircraft. The vortex core is relatively small--only a few hundred kilometers across. An airplane can traverse it 5-10 times in the course of a flight lasting 6-8 hours. The great rotational inertia of the swirling wind means that the balanced vortex changes slowly during the time that an airplane can remain on station. Expendable probes can report atmospheric or oceanic conditions as they drop from flight level. The size of the core is comparable with the range of 5 or 10 cm wavelength search radars. Although aircraft radars are relatively low powered and have small antennas, the ability to move through the storm enables them to observe storms in detail. The foregoing advantages compound for aircraft equipped with Doppler radars, particularly so if they can fly coordinated patterns in pairs to produce true dual-Doppler winds. NOAA's aircraft operations center flies two WP-3D turboprop that represent a unique scientific resource and are the mainstay of HRD's annual campaign of airborne hurricane observations. Starting in 1997, a third aircraft, a Gulfstream IVSP jet entered the inventory. This airplane is dedicated to synoptic surveillance to obtain observations in the environment around hurricanes to improve operational track forecasts.