TOPIM – Modelling hurricane Intensity in the Caribbean Region

Tropical cyclones are one of the most frequent and costly disasters affecting the Small Island Developing States (SIDS) in the Caribbean.Historical analysis of tropical cyclones in the Caribbean Region (10-30°N 55-90°W), using HURDAT data, shows that the mean Maximum Sustained Wind (MSW) has increased significantly by 30kts since 1965, a rate of 5.3kts per decade with a corresponding significant decrease in the minimum pressure of 2.3mb per decade. The increasing MSW observed is significantly correlated with the August, September and October (ASO) ocean temperatures, which are rising at 0.2ºC per decade in the Caribbean.TOPIM - Tropical cyclone Ocean-coupled Potential Intensity Model has been developed to better predict tropical cyclone intensity in the Caribbean. TOPIM is an ocean-coupled dynamical and statistical model which has been developed for the Caribbean and already has proof of concept, having been working experimentally for Bermuda since 2021. TOPIMuses subsurface ocean temperature from Argo floats and atmospheric sounding data to improve the prediction of tropical cyclone intensity (wind strength and minimum pressure) in near real-time, using little computing requirements. The model calculates the expected TC potential intensity based on; the average temperature over the top 100m ocean layer in the Caribbean, the local atmospheric sounding data, and local wind pressure relationship for past hurricanes in the area since 1965. The top 100m layer is chosen as it provides the closest prediction of hurricane intensity in the Caribbean region on a hindcast basis since 1990. Results show the prediction better forecasts actual tropical cyclone potential intensity than models using sea surface temperature alone.TOPIM can also be used for future scenario planning. Past storms can be placed in a warmer ocean environment, to understand the expected increase in maximum sustained wind - an ocean sensitivity analysis. The analysis assumes the atmospheric sounding conditions remain the same. Analysis of historical Caribbean storms suggests a 27kt increase in intensity on average for a 1°C rise in ocean temperature over the top 100m layer.(Hallam et al. Modelling hurricane Intensity in the Caribbean Region, in prep.)https://www.topim.org