Tropical Cyclone Observation and Forecasting with and without Aircraft Reconnaissance

The contributions of aircraft reconnaissance to the accuracy of tropical cyclone center positioning, motion, and intensity determinations are examined, along with their impact on the accuracy of track and intensity forecasting. The analyses concentrate on differences in cyclone position and intensity diagnosis, as well as track forecasting during periods when aircraft measurements were made versus times when aircraft data were not available. Northwest Pacific data for the period 1979–86, which contain over 200 tropical cyclone cases with approximately 5000 center fix positions, were used for the analyses. Aircraft versus no-aircraft situations are examined with respect to the class of satellite data that were available and for day versus night measurements. Differences in positioning and intensity estimates made from simultaneous independent satellite observations are also examined. Results show that satellite analysts operating independently frequently obtain large differences in their estimates of tropical cyclone positions, as well as their intensity estimates. Aircraft reconnaissance of cyclone position and intensity, as were flown in the western Pacific, does not appear to improve track forecasts beyond 24 h, nor does it affect the current 12-h motion vector estimate. Other areas of tropical cyclone warning services, including estimates of current position and intensity as well as short-term estimates of motion, especially for recurvature forecasts, appear to be improved by aircraft data.