February 29, 2008 -- For the first time, America’s entire fleet of aircraft that fly through hurricanes now have instruments that measure surface winds, giving forecasters at NOAA’s National Hurricane Center a better view of the intensity and the size of these powerful storm systems.

The instrument, known as a stepped frequency microwave radiometer, attached to the wing of each aircraft detects radiation that is naturally emitted from foam created on the sea by winds at the surface. Computers onboard the aircraft then determine surface wind speeds based on the levels of microwave radiation detected.

In the past, aircrews extrapolated wind speeds from the aircraft's altitude or from a GPS dropsonde released from the aircraft. The stepped frequency microwave radiometer provides a continuous measurement of surface winds giving NOAA’s National Hurricane Center forecasters a more complete picture of the storm. The instrument can also determine rainfall rates within a storm system. This, in addition to wind speeds at flight level, provides structural detail of the tropical cyclone.

The current generation of this radiometer was first used on NOAA’s two WP-3D Orion aircraft in 2003 for research flights and then used operationally in 2005. Installation on the ten WC-130J hurricane hunter aircraft flown by the Air Force Reserve 53rd Weather Reconnaissance Squadron began in 2006 and was just completed.