Hurricane Melissa Could Drop Two Feet of Rain on Jamaica

Near-Hurricane Melissa Will Drop Mind-Boggling Rain on Jamaica

By Meghan Bartels edited by Andrea Thompson

Tropical Storm Melissa is poised to devastate Jamaica and parts of Haiti this weekend as the slow-moving storm rapidly explodes into a major hurricane and dumps huge amounts of rain on the Caribbean islands. Some areas could see as much as 20 inches of rainfall in just a few days. With that depth, an Olympic swimming pool’s worth of water would cover scarcely less than the area of a football field.

Winds are the threat that is most associated with hurricanes, followed by storm surge. But rain is an often overlooked peril of such storms—and can be the most dangerous one. That was the case with 2017’s Hurricane Harvey—which established the record for rainfall in a single storm in the continental U.S. when it dropped more than 48 inches of rain near Houston—and with last year’s Hurricane Helene—which dropped as much as two feet of rain in Appalachia just days after previous rainfall of approximately one foot in the region.

READ MORE: Hurricane Science Has a Lot of Jargon—Here’s What It All Means

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As of the afternoon of October 23, Melissa is a tropical storm with a peak sustained wind speed of 45 miles per hour, according to the National Oceanic and Atmospheric Administration’s National Hurricane Center, which is operating despite the now three-week-long, continuing shutdown of the federal government. The storm is expected to become a hurricane within 48 hours and to intensify to a major Category 3 hurricane by Sunday—after which it will perhaps top out as a Category 4 hurricane by Monday. (Forecasters are still watching to see whether Melissa might threaten the continental U.S. next week.)

But even as the winds within Melissa are forecast to become powerful gusts, the atmosphere around the storm is calm, leaving the would-be hurricane meandering through the Caribbean. Melissa’s eye is currently moving at a speed of just two miles per hour. “You or I could walk faster than it’s moving,” says Brian McNoldy, a hurricane researcher at the University of Miami. All of the threats of a serious hurricane are exacerbated when a storm moves slowly because any given place is exposed to hurricane conditions for more time. “Getting hit by a hurricane is never good,” McNoldy says. “But getting hit by a hurricane that’s not moving is so much worse.”

As Melissa crawls by, it will dump huge amounts of rain on the islands in its path. The National Hurricane Center’s rainfall forecasts currently see western Jamaica getting nearly a foot of rain within the next three days, with some locations surpassing that. But the storm’s timeline is currently longer than the forecast’s; former NOAA meteorologist Alan Gerard expects some parts of the Caribbean to see at least 20 inches of rain from Melissa.

More intense rainfall events from storms of all kinds are becoming more likely as warming temperatures prime the atmosphere to hold more water vapor. “That is the fingerprint that climate change has on storms—in general, more moisture, more rain,” McNoldy says.

He worries that Melissa’s devastation in the Caribbean will be worsened by the mountainous terrain of islands such as Jamaica and Hispaniola, which is divided between Haiti and the Dominican Republic. Such a landscape is particularly vulnerable to flash floods and landslides because water rushes to the lowest elevation it can find—consider the terrible flooding Hurricane Helene brought to Appalachia last autumn. In addition, mountainous landscapes can worsen rainfall itself because when an air mass hits a mountainside, it is forced upward, which causes it to drop more of the water inside of it, McNoldy says.

The combination could be a recipe for dire flash flooding, which is particularly dangerous in steep terrain that funnels huge amounts of water into small areas. “Once you’re over even half a foot of rain, it’s a ridiculous amount of rain,” McNoldy says. “When you’re getting into 12-plus inches of rain, it’s just too much for anywhere to handle, no matter how good your infrastructure is.”

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