Tropical cyclones generally exist in the data-sparse oceanic belt extending from near the Equator to the subtropics. Accurate tropical cyclone track and intensity forecasting depends upon improvements to the observational network in these regions, and on accurate analysis and assimilation of these observations into numerical guidance. Between 1982 and 1996, the National Oceanographic and Atmospheric Administration (NOAA) Hurricane Research Division (HRD) conducted twenty "Synoptic Flow" experiments in the North Atlantic basin to gather observations in the tropical cyclone core and environment and assess their impact on the numerical guidance. Dropwindsonde observations from "Synoptic Flow" experiments produced significant improvements in the primary numerical guidance for the National Hurricane Center (NHC) official track forecasts.

Due to the success of this research project, in 1996, NOAA procured a Gulfstream IV-SP (G-IV) jet aircraft, and put it to use in operational "Synoptic Surveillance" missions in the environments of tropical cyclones threatening the continental United States, Puerto Rico, the Virgin Islands, and Hawaii. A new dropwindsonde, based on the Global Positioning System, was developed by the National Center for Atmospheric Research to replace the ODW. The great success of this program has led to the adoption of the idea of surveillance by scientists in Taiwan, who conducted their first operational missions during the 2003 typhoon season. It has also led to the development of a parallel program to improve numerical forecasts of severe winter weather with the G-IV, and is to culminate with the Globa l THORPEX program over the next several years. The current presentation will summarize the important findings and results from these programs, and look at hopes for the future.