Are hurricanes getting stronger?

Late summer is typically hurricane season in the tropics, and in 2017 hurricanes Harvey and Irma have wreaked havoc across the Caribbean and southern USA. Irma is the largest such storm we’ve ever seen. Katie Haylor has been looking at the science behind these extreme weather systems...

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Katie - Hurricane Irma is now one of the most powerful storms on record in the Atlantic basin. With winds reaching upwards of 180 miles an hour, the storm has decimated homes and caused chaos across the Caribbean and parts of the USA. Here’s tropical meteorologist Nick Klingaman, from the University of Reading…

Nick - A hurricane is a very large, organised, cluster of thunderstorms essentially, and they can be hundreds, if not thousands, of kilometres across. They tend to form across very warm tropical oceans where there’s lots of heat and moisture available to feed into these thunderstorms. Hurricanes are always associated with an eye in the middle and then these tightly rotating spiral arms of thunderstorms that come out around them.

Hurricanes need a few ingredients to be able to form. First of all, they need very warm ocean surface temperatures so that they can extract a lot of heat and energy from the ocean. They need moisture available in the atmosphere which is why they tend to form in tropical oceans where it’s quite warm and most. They also need a source of rotation because hurricanes are very tightly packed, organised, rotating clusters of thunderstorms, and these sources of rotation often come from waves in the atmosphere…

Florida is now feeling the full force of hurricane Irma. It’s spent many days moving across the Caribbean…

Nick - Forecasts of hurricane intensity tend to be quite reasonable these days. Often we can predict the intensity of a storm several days to a week in advance of it making landfall. Forecasts of the intensity of hurricane Irma, for instance, were highly accurate and we knew days in advance this was going to be a very severe storm for the islands in the Caribbean and for the South East of the United States.

我们使用高分辨率天气预报dels which run on massive supercomputers with tens of thousands of processors to forecast these storms and, indeed, the weather worldwide. Those computer models require observations of the atmosphere all around the globe. And particularly for hurricanes, we get additional observations from reconnaissance aircraft which fly out literally into the storms dropping probes and taking measurements with instruments onboard the aircraft to feed those data into our computer models to help us better predict the track and the intensity of these storms.

Katie - So these are manned aircraft that are literally flying into the storm?

Nick - These are manned aircraft. They’re operated by organisation like the National Oceanic and Atmospheric Administration in the United States, and they do fly right into the storm of all intensities. At the peak of hurricane Irma when the winds were 170/180 miles an hour, you had reconnaissance aircraft flying in there around the clock.

Katie - Rising global temperatures means there’s more energy and more water in the atmosphere. So, considering the devastation Irma has caused for thousands of people, what would the hurricanes of the future be like?

Nick - We do expect that with climate change hurricanes will become more intense. We don’t necessarily expect that they’ll become more frequent but we do expect that they’ll become a little bit stronger. Particularly we might see strong winds, more intense precipitation associated with hurricanes, and stronger storm surges because of sea level rise.