Bapon (SHM) Fakhruddin, PhD

Cyclones typically lose power once they move over land. However, new research shows that if the storm passes over warm, soaked ground, the moisture and heat from the soil can re-energize the hurricane. This mimics the way that the warm ocean usually fuels the storms.

As climate change increases extreme weather events, understanding this phenomenon is crucial. To better predict storm paths and intensities, we developed coastal inundation forecasting models for Bangladesh, the Dominic Republic and Fiji using total water scenarios in 2015-2019, and those are now operational models for countries cyclone #EWS for saving lives and risk-based decision-making. It’s time for models to address new phenomena to account for the influence of soaked land in re-strengthening storms. Accurate forecasts can save lives by warning inland residents of danger.

In 2018, Hurricane Florence demonstrated this brown ocean effect. Although relatively weak upon landfall, its rains intensified as Florence moved across the already-flooded Carolinas. This led to catastrophic flooding. The satellite data analysis revealed this positive feedback loop – the existing wet soils enhanced further extreme rainfall. Higher pre-storm soil moisture and temperature also contributed.

This effect helps inland storms last longer and travel farther before dissipating. We saw this with Tropical Storm Erin in 2007, Cyclone Nargis in 2008, and Hurricane Ida in 2021. The data shows that the brown ocean effect can give new life to weakening storms, given the right conditions.

Soil-fueled cyclones. Humidity from warm, wet soil and trees injects energy into hurricanes and tropical storms as they travel over land, resulting in intense bursts of rainfall. This phenomenon, dubbed the brown ocean effect, has now been confirmed with observations.

We also did a probabilistic cyclone modelling you may find interesting to read: Understanding hazards: Probabilistic cyclone modelling for disaster risk to the Eastern Coast in Bangladesh https://www.sciencedirect.com/science/article/pii/S2590061722000035