Prediction of Tropical Cyclone Rapid Intensification Events
Abstract
The largest errors in tropical cyclone intensity forecasting are usually the result of rapid intensification events, where rapid intensification is defined as a change in minimum central pressure of at least 42 hP sub a in a 24 hour period, or a satellite-inferred increase in maximum sustained winds of a least 23 m/s 1 per day when no measurement of central pressure is possible. An observational and theoretical study is made of the unique characteristics of rapidly intensifying typhoons in the western North Pacific. Climatological data, digital infrared satellite imagery and composited rawinsonde sounding data within 5 deg of the center of tropical cyclones were used to identify the distinctive features associated with rapid intensifiers when compared to other stratifications of non-rapid intensifiers and non-intensifiers. Rapid intensity change is indicated on satellite imagery as an extreme concentration of convection near the cyclone center. Relative concentrations of inner and outer deep cumulus convection reveal a predictive relationship between the ratio of inner core to outer core convection and the onset of rapid intensity change 12 hours later. This prediction technique was found to successfully forecast rapid or non-rapid intensification in over 90% of the cases in a three-year study of 70 northwest Pacific tropical cyclones. A physical explanation of the likely processes associated with rapid intensification is also presented. Rapid intensification is believed to be the result of weak asymmetrical wind flow across the cyclone at upper levels of the troposphere. Rapid intensifiers are shown to have large warm anomalies near the tropopause and weak vertical shear of tangential winds below 150 hP sub a. Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 03, 1990
- Accession Number
- ADA227668
Entities
People
- Dan B. Mundell
Organizations
- Air Force Institute of Technology