Both ground based and aircraft based wind shear alerting systems are currently available and in use to support aviation safety. This article focuses on the ground based wind shear hazard measurement and alerting methods. Primary topic will be the Terminal Weather Information for Pilots (TWIP) system and its potential positive and negative impact on commercial aviation operations in general and at Northwest Airlines specifically.

An analysis of the reliability of the TWIP system was completed and reported at the 9th Conference on Aviation, Range, and Aerospace Meteorology in September 2000. This report provides new information and analysis. Similar to the first, the bulk of the analysis deals with wind shear alerts produced during weather conditions described by the TWIP system as “No Storms With In 15nm”. These type of conditions are potentially the most insidious because they are times when Level I (less than 30 dBz) reflectivity of convection or no convection at all is detected.

The benefits of the TWIP system during weak convection and weather conditions with no convection are described using examples of successful wind shear hazard detection (e.g. dry regime microbursts, wind shear associated with synoptic scale frontal systems). The short comings of the system will also be described using examples of wind shear alerts of questionable validity.

The conclusion identifies improvements made since September 2000 as well as recommendations for additional possible improvements.