The National Center for Atmospheric Research (NCAR), in a joint effort with the National Oceanic and Atmospheric Administration (NOAA), has developed a dropwindsonde based on Global Positioning System (GPS) satellite navigation. The NCAR GPS dropwindsonde represents a major advance in both accuracy and resolution for atmospheric measurements over data-sparse oceanic areas of the
globe, providing wind accuracies of 0.5-2.0 m/s with a vertical resolution of roughly 5 m. One important advance over previous generations of sondes is the ability to measure surface (10-m) winds.
On August 3, 1997, the NOAA/Hurricane Research Division deployed 10 GPS sondes in the eyewall of Hurricane Guillermo from one of the two NOAA WP-3D research aircraft. These represent the first high-resolution wind and thermodynamic soundings of a hurricicane eyewall. Roughly 80 GPS dropwindsondeswere released within 300 km of Hurricanes Guillermo, Erika, and Linda during the 1997 Atlantic and Pacific seasons.
In this paper we examine the vertical structure of hurricane winds using the GPS dropsonde data. The soundings reveal unprecedented detail of the structure of the hurricane eyewall and boundary layer. Of particular interest to the forecast and warning process is the relationship between flight-level reconnaissance winds, typically at 700 mb, and surface winds. Some preliminary stratifications of the soundings by convective environment (eyewall, rainband, stratiform, etc.) are presented.