The primary purpose of operational synoptic surveillance missions (using the NOAA G-IV aircraft) is to deploy targeted GPS dropwindsondes in the environment of a tropical cyclone, to improve 1-3 day forecasts of the cyclone's track and intensity. The present technique used to identify locations for targeted observations to be taken is based on the "spread" of an ensemble forecast. However, this technique does not account for observations that are to be assimilated into the forecast models, or the variance of the tropical cyclone forecast of interest.

The Ensemble Transform Kalman Filter (ETKF) is one objective targeting strategy that accounts for the assimilation of observations, and the effects of targeted observations on forecast error variance. It is presently used for Winter Storm Reconnaissance, and its applicability for Tropical Cyclone reconnaissance is the subject of this presentation. Comparisons between the ETKF and the presently operational ensemble spread technique will be made for several tropical cyclone cases, using the NCEP GFS and ECMWF ensembles. Necessary modifications to the ETKF for use in tropical cyclone targeting will be discussed.