Tropical cyclone intensity forecasting can prove problematic, especially when rapid intensity changes are involved. In recent years several systems that underwent rapid intensification developed a very small eye in the process, often referred to as a ‘pinhole' eye. Understanding the processes and factors involved in the development of these pinhole eyes could identify links with rapid intensification and better predict both phenomena.

This project develops a climatology of pinhole eyes occurring in tropical cyclones in the Atlantic basin over the period 1989-2006. For this study pinhole eyes are defined as those eyes with a diameter smaller than 10 n mi, representing less than ten percent of the eye size measurements available in the aircraft reconnaissance fixes. A combination of aircraft reconnaissance fixes, operationally-estimated size parameters, and synoptic data is used to examine the size and intensification properties of pinhole cases, as well as their large-scale environment.

Preliminary results indicate that, while pinhole eyes were defined to include less than 10 percent of eye measurements, 40 percent of the tropical cyclones with eye measurements had at least one pinhole eye measurement in their lifetime. These systems were spread throughout the domain covered by the aircraft, but overall a preference for smaller eye sizes was found in the Caribbean Sea and Gulf of Mexico. This is consistent with expectations of pinhole eyes in areas of higher ocean heat content and lower latitudes.