A radiosonde is a small instrument package and radio transmitter that is attached to a large balloon. As the balloon rises through the atmosphere, the radiosonde instruments measure: Air Temperature, Humidity and Pressure. This data is relayed back to a computer at the surface.

The data provide an important vertical profile of the hurricane’s environment, which is critical for forecast models. Radiosondes are generally only released over land, which leaves a large data gap over the oceans.

Dropsondes are a variation on the radiosonde. Instead of being carried aloft by a balloon, the dropsondes, which are attached to a small parachute, are dropped into the hurricane from the reconnaissance aircraft. These instruments are helping forecasters to make great strides in understanding and predicting hurricane behavior.