Climate change and the 2017 Atlantic Hurricane season

June 1 is the official start of the Atlantic Hurricane season, which covers the North Atlantic Ocean, the Gulf of Mexico and the Caribbean Sea, and it runs until November 30, 2017.

That doesn’t mean to say we cannot see a tropical storm or hurricane develop outside of these dates. In fact, the first tropical storm of 2017, Arlene, has already been and gone, developing on April 20 in the central Atlantic.

According to the National Hurricane Center, April tropical storms are rare, and this was only the second since the use of satellites, the first recorded was in 2003, Tropical Storm Ana.

Each year, in the lead-up to the official start of the season, various weather organisations will release their forecasted predictions for the number of storms developing and the severity of those storms expected.

This year, both the National Oceanic and Atmospheric Administration (NOAA) and the Colorado State University (CSU) hurricane forecast team, are predicting average to above-average storm activity.

An average Atlantic season has 12 named storms, six hurricanes and three major hurricanes.

NOAA are predicting 11 to 17 named storms, five to nine will develop into hurricanes and two to four intensifying into major hurricanes.

The CSU team predicts the season will produce 11 named storms, of which at least four will develop into hurricanes and two intensifying into major hurricanes.

There will always be a degree of variance over these forecasts and this year the predictions differ because of disagreement over the development of an El Nino in the eastern Pacific and sea surface temperatures in the Atlantic.

NOAA states “a weak or non-existent El Nino, resulting in near or above-average sea surface temperatures across the tropical Atlantic Ocean and the Caribbean Sea and average or weaker-than-average vertical wind shear in the same region.”

CSU says “a weak to moderate El Nino could develop by the peak of the Atlantic hurricane season and the tropical Atlantic now is slightly cooler than normal and that is associated with a more stable atmosphere and drier air – both of which suppress organised thunderstorm activity necessary for hurricane development.”

As well as the widespread damage caused by the winds coming from a hurricane, storm surge and rainfall are both hugely damaging and deadly. Both of these factors are two areas where climate change is exerting influence on the overall damage produced by hurricanes.

As global temperatures rise, sea level rises too, meaning storm surge can reach further inland. Rising temperatures also concentrate moisture in the atmosphere, providing more “fuel” for heavy rains.

The effect of climate change on hurricanes is an active area of research and although there is, as yet, no firm conclusion, the general consensus is that there may be fewer storms overall in a warmer world, but a higher proportion of them will be major hurricanes. Indeed, we have seen a general increase in the destructive power of hurricanes since the mid-1970s, when the period of the most rapid increase in global ocean and land temperatures began.

Some research has also suggested that the hurricane season could become longer, meaning more pre-season storms like Arlene.

Once the 2017 Atlantic Hurricane season gets under way, the initial forecast will be revised with NOAA issuing an update in early August, just prior to the season’s September peak.

Whatever the differing opinions may be on the number and intensity of this year’s projected storms, the one area all scientists and organisations can agree on, is that those living in hurricane-prone regions prepare for the season ahead.

Prepare, have a plan, listen to your local media for storm information and take action when advised to do so.