The Modification of the Water Vapor Profile during the Passage of a Tropical System

During August and September of 1998, the third Convection and Moisture Experiment (CAMEX-3) was conducted from Andros Island, the Bahamas. The goal of the program is to improve hurricane and tropical storm prediction and increase the understanding of these systems. As part of CAMEX-3, NASA Goddard Space Flight Center provided frequent radiosonde launches to detail the vertical profile of the atmosphere from Andros Island.

Some particulars of the vertical moisture structure are examined, with a focus on the changes associated with the near-pass of Hurricane Bonnie during the later part of August. Bonnie passed within 520 km of Andros Island on August 25,1998. Several other stations are also examined including Key West, Miami, and Jacksonville, Florida, and Bermuda. The system made the nearest approaches to these sites at 480-900 km.

The results of this examination indicate a substantial change in the vertical distribution of precipitable water (PW) at Andros during Hurricane Bonnie's pass, with some layers within roughly 500-700 hPa experiencing a up to a 50% decrease in PW, compared to the average PW during CAMEX-3. This illustrates the large-scale alteration of the atmosphere by Bonnie extending to areas well ahead of the storm. The other stations showed similar changes when Bonnie made her closest approach to them.