Dropwindsonde

A dropsonde is an expendable weather reconnaissance device created by the National Center for Atmospheric Research (NCAR), designed to be dropped from an aircraft at altitude over water to measure (and therefore track) storm conditions as the device falls to the surface. The sonde contains a GPS receiver, along with pressure, temperature, and humidity (PTH) sensors to capture atmospheric profiles and thermodynamic data. It typically relays these data to a computer in the aircraft by radio transmission.

Since the early 1970s, hurricane hunters have employed dropsondes while flying over the ocean to obtain meteorological data on the structure of hurricanes deemed to be of possible concern to land locations in the northern Atlantic and northeastern Pacific oceans. Dropsonde instruments are typically the only way to measurement the wind and pressure near the sea surface within the core of such cyclones, allowing meteorologists to reliably establish the storm's intensity and size. The data obtained is typically fed into supercomputers for numerical weather prediction, enabling forecasters to better track and predict what will happen to the hurricane. During a typical hurricane season, the 53d Weather Reconnaissance Squadron Hurricane Hunters deploys 1000 to 1500 sondes on training and storm missions.

Aircraft reconnaissance missions are also sometimes requested to investigate the broader atmospheric structure over the ocean when cyclones may pose a significant threat to the United States. These interests include not only potential hurricanes, but also possible snow events (like nor'easters) or significant tornado outbreaks. The dropsondes are used to supplement the large gaps over oceans within the global network of daily radiosonde launches. Typically satellite data provides an estimate of conditions in such areas, but the increased precision of sondes can improve forecasts, particularly of the storm path.

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Wikipedia