Ask the Meteorologist: How often do droughts happen after hurricanes?

There has been a huge difference between the rain we saw before Helene vs. the rain we’ve seen since Helene.

It turns out there was a study in 2022 at Florida State University that looked into how often drought developed after landfalling tropical systems.

Since 2000, it’s actually rare to see that happen.

Four of the 30 storms analyzed had a flash drought develop shortly after their landfall. It happened after storms like Humberto (2007), Isaac (2012), Matthew (2016) and Harvey (2017) and often coincided with a more widespread, pre-existing drought.

In three of the four cases, the drought began within days after landfall. After Isaac, it took a couple of weeks after landfall for drought to settle in.

The large-scale weather pattern oftentimes becomes less conducive for storm development once a tropical system passes through. This could be due to cooling waters left behind.

It could also be due to the sinking air that’s often found on the southwestern side of a tropical system. Think about it. A tropical storm or hurricane passes through. Days later, the sky is clear and the air feels refreshing. That’s exactly the sinking air we’re talking about.

I looked into the path Helene took, and I overlaid it with the current drought (as of November 14, 2024). Drought continues in areas south and west of the storm’s center.

However, if you were to look at the Drought Monitor in the week leading up to Helene’s landfall, you’ll notice those areas were already in a drought.

Could it be that Helene was one of these unique cases of flash drought in response to a tropical system?

The study says that, while rare, the sample size is too small to either conclude or negate a direct link between landfalling storms and flash drought immediately afterward.