Climate Change Drives Hurricane Melissa’s Rapid Intensification in Caribbean

Satellite image of Hurricane Melissa captured on Tuesday. Credit: NOAA/AP.

The ultra-warm water that has enveloped the Caribbean Basin for a long stretch this summer created extremely favorable conditions for storm development. When Hurricane Melissa finally intensified and struck Jamaica’s coast on Tuesday, this warm body of water lifted the storm to monster status: a Category 5 hurricane with winds up to 185 mph – one of the most powerful storms to ever touch land in the Atlantic.

Experts see this as a clear example of how climate change can raise risk: they saturate storms with heat and moisture, making them more destructive and harder to forecast than storms of years past.

Jamaica wakes to the destruction: damaged infrastructure, shattered power grids, hospitals and schools. A full assessment of the losses in the hardest-hit areas may take days, as rescue services and families continue to search for the missing and restore access to damaged areas.

Three days before landfall, Melissa experienced two periods of rapid intensification, when sea-surface temperatures were about 2.5 degrees Fahrenheit warmer than average for this time of year.

Human-caused climate change has made such warm water much more likely, according to the Climate Central research group.

And as the storm moved across these waters, its maximum winds rose from 70 mph (tropical storm) to 140 mph – and within a day it was a Category 4 storm.

Climate change as a driver of storm intensity

Such a rise in storm intensity is becoming an increasingly common phenomenon. “We have observed a notable surge in the pace of exponential intensification, with winds increasing by at least 60 mph within 24 hours in most ocean basins over the past four decades,” explained Steve Bowen, Chief Science Officer at Gallagher Re. “This is what scientists have expected – that warmer oceans will support storms to the highest intensities.”

“Over the past four decades we have seen a marked rise in the pace of exponential intensification: winds increasing by at least 60 mph within 24 hours in most ocean basins.”

“This is the third Category 5 tropical cyclone in the Atlantic this year, and the previous two also went through periods of rapid intensification,” said Kerry Emanuel, hurricane scientist at MIT, in a CNN interview. “Taken together, this season may be in line with what we’ve been saying for a while: the share of global tropical cyclones reaching high intensity is rising, and the number of storms that rapidly intensify is increasing.”

This season is also considered “quite normal” in the number of Atlantic tropical storms and hurricanes, according to Emanuel’s findings, which align with studies suggesting that warming the world does not necessarily lead to more tropical cyclones in a season.

But other studies indicate that as climate warms, tropical storms and hurricanes can bring heavier rainfall. This is because warmer air can hold more moisture, and heated seas also promote the evaporation of more water vapor into the atmosphere, giving storms additional energy.

Ocean temperature remains the main driver of storm strength: recent research estimates say Melissa reached the so-called maximum potential intensity – a metric developed to determine how strong a storm can become given the current environmental cues. Such cases are rare due to upper-atmosphere interference, but Melissa showed that with warmer oceans this is possible, Emanuel noted.

“Very warm water almost certainly has a human fingerprint, and there is no doubt that this warm water played a key role in Melissa’s intensity and the pace of its intensification.”

Other experts also point to rapid storm intensification while dwelling in a basin of abnormally high sea-surface temperatures and waters that reach into deeper depths. However not all aspects of the storm are easily attributable to climate change – notably its slow movement. “Perhaps the most important is to understand that not all storms will be able to take advantage of the elevated threshold due to higher sea temperatures, but some will, and this one did,” Swain noted.

“When such situations occur, near densely populated areas where impacts can be catastrophic, the damage from climate change becomes substantially greater.”

Scientists also note: not all aspects related to Melissa reflect global warming, but rising ocean heat content and a deeper distribution of heat create the groundwork for new patterns of extreme storms. However some factors – notably the storm’s slow movement – require further study and clarification within the framework of global climate change.

To sum up, Melissa has become a clear example of how ocean warming can amplify the strength and duration of hurricanes, increasing risks for people in the Caribbean Basin and beyond. Extreme storms continue to leave scientists with the task of a deeper understanding of the connection between climate change and future storm seasons, in order to better prepare for future challenges.