Hurricanes and Southbound Sailing Plans

If the prospect of 1,500 miles of ocean sailing weren’t enough to put nerves on edge, crews aboard 115 boats queued up for the Salty Dawg Sailing Association (SDSA) Caribbean Rally last November were also confronted with on-the-nose tropical winds—winds that eventually strengthened into Hurricane Nicole.

Pinned against the Eastern Seaboard for nearly two weeks past the end of the official hurricane season, rally Director Bob Osborn was asked more than once, “Is this normal?”

“It’s very easy for us to say global warming is affecting us now,” he said in a call months later from Antigua. “Was this year’s delay a direct result of global warming? Or was it a variation in the weather? I don’t know.”

Sailors, like telltales, are sensitive to small changes in the environment. They’re out there in it, trained to adjust quickly. Every season they watch Jim Cantore bend into the wind. They’ve seen an endless series of stories about the coming climate apocalypse: heat waves, shrinking glaciers, flooding of coastal cities, the collapse of seaside homes, the forced migration of island dwellers.

And when a hurricane strikes the U.S, the loss of lives, homes, and boats, the disruptions, the cost in billions of dollars is top news for weeks. With that comes insurance premiums for boats rising by 200 to 300 percent, most of it in the last 5 to 10 years, reports John Fisher, managing director of Risk Strategies, a major insurance broker. He estimates that 40 to 50% of that increase can be attributed to the industry’s reaction to climate change.

It’s hard not to assume the worst, and as cruisers gear up for another season in the Caribbean, the question to ask is, how may climate change affect them? The answer, we found, is complex and surprising.

First, there is no question that global warming is “here and now,” as NOAA oceanographer William Sweet likes to say. The atmosphere is warmer, so the seas are warmer and higher—rising on the East and Gulf coasts at a rate of 4 to 5 millimeters a year, about an inch every five or six years over the last several decades. This is due largely to ice melt in Greenland, Antarctica, and mountain glaciers. Thermal expansion of sea water is adding 1.3 millimeters a year, about one-third of the rise.

At that rate, Sweet predicts sea levels will rise about 12 inches along the East and Gulf coasts in the next 30 years, and 6 to 8 inches in the Caribbean. It took the last century for that same rise.

All that warming—2°F in the atmosphere, 1.5°F in water since 1880—creates more water vapor, the fuel for storms, and so it would not be unreasonable, especially in light of the headlines, to believe that Atlantic hurricanes are becoming dramatically stronger and more frequent. But researchers say actually, that’s not the case.

“What the computer modeling and the theory suggest is that we are having stronger hurricanes now and in the future. But the changes now are maybe 1% stronger. So, something that in pre-industrial time would have been a 100-mile-per-hour hurricane is now 101,” says Christopher Landsea, the National Hurricane Center’s branch chief for tropical analysis and forecasts.

“And even by the end of this century, even assuming quite a bit of additional warming, you’re only looking at 3 or 5% stronger. We’re looking at so small a change today, we can’t even measure it.”

Perhaps even more startling is “growing confidence that there’ll be fewer tropical storms and hurricanes,” Landsea says. “So even though, thermodynamically, it may be slightly more conducive for hurricanes to get a little bit stronger, other factors, including the mid-level humidity and wind shear between the ocean surface and about 8 miles up, may make it more difficult to reach out to that potential.”

This conclusion is still being studied and debated in the scientific community, but most models “project a decrease (or little change) in the global frequency of all tropical cyclones combined,” writes Tom Knutson, NOAA’s senior scientist at the GFDL (Geophysical Fluid Dynamics Laboratory) model laboratory at Princeton University. He notes, however, that “confidence levels” for this “can vary between authors within a given report.”

One thing is certain: With more evaporation of seawater into the atmosphere, rain will increase 10 to 15% in and around tropical cyclones, Knutson reports.

But what sailors may perceive as climate change may well be variations in weather, notes Chris Parker, a Florida-based meteorologist and author of Coastal and Offshore Weather, whose company, Marine Weather Center, provides forecasts and routing advice for the Salty Dawg rally as well as other sailors and boaters. “Some people say we’re seeing more out-of-season tropical weather. That’s true. But out-of-season tropical weather could be here anyway even if it weren’t for climate change. Named tropical storms have occurred in every month of the year in the northern Atlantic—even in February. That would surprise a lot of folks to know this.”

Also, at this writing, it appears that El Niño, the Pacific system that varies year by year, will be warmer this season, which dampens hurricanes in the Atlantic.

Parker and two other routing services contacted for this story said they have seen nothing that can be attributed to climate change that would change how and where they route boats to the Caribbean and back home.

The most visible effect of global warming on tropical storms, now and into the future, is the storm surge.

“If you have 2 or 3 feet of additional sea level rise by the end of the century, every single hurricane that hits is going to be that much worse for the storm surge and flood,” says Landsea. “That, to me, is the biggest concern about global warming and hurricanes. It’s not the wind, but it’s the flooding.”

Repetitive flooding along the U.S. coastline is the “new norm” and is accelerating, NOAA’s Sweet says. “This problem is going to go chronic rather quickly. It’s not going to be a slow gradual change.”

In Annapolis where he lives, for example, flooding 2 to 3 feet above average high tide, labeled “moderate” flooding, is fairly common and frequent because wind pushes water over the wide continental shelf.

This flooding also varies by area because of regional subsidence of the ground. In the Gulf Coast, oil pumping is causing the ground to sink at the rate of an inch every three years at the mouth of the Mississippi and an inch every five years in Texas. On the East Coast, from New York to Virginia, the melting of the 15,000-year-old Laurentide ice shield, which shoved the earth’s mantle toward the eastern U.S., is allowing the mantle to slowly return to its original position, so the area is sinking. The subsidence in mid-Atlantic is about 2 millimeters a year—an inch every 10-15 years.

Because of geology, with deep narrow continental shelves, even minor flooding is still rare in Caribbean islands. By 2050, that kind of flooding will occur several times a year, Sweet said.

The U.S. Coast Guard reports that the “tempo of incidents, crises, and disasters, to which the Service must respond are on the rise. The increase will likely continue. Climate change induced sea level rise and ocean warming are key contributing factors.” They declined to provide examples.

There is one bit of good news for sailors: Hurricane forecasting has never been more accurate. The National Hurricane Center now has a two-day average landfall error rate of 60 miles, down from 250 miles in the 1980s. The five-day average is 175 miles.

“That’s been a big success story,” thanks to computer modeling, satellite data, and imagery, Landsea says.

The 2023-24 Hurricane Season Outlook

With the certainty of a dice roll, NOAA is predicting a “near normal” 2023 hurricane season. That could mean 12 to 17 named storms, five to nine hurricanes, and one to three that could reach Category 3 to 5. The prediction, announced one week before the start of the hurricane season in June, called for a 40% chance of a near-normal season, a 30% chance above-normal and 30% below normal. NOAA’s confidence in these ranges: 70%. 

The uncertainty is due to a warm El Niño. Models suggest that if it arrives, it will dampen hurricane generation in the warm Atlantic. Predictions from Colorado State University land in the middle of NOAA’s ranges: 12 named storms lasting 55 days, six hurricanes lasting 25 days, and two major hurricanes of five days. 

NOAA administrators say new tools for tracking storms, pinpointing landfalls, and predicting intensities, including new computer programs, satellites, sail drones, buoys, and underwater gliders, will give sailors as much as two extra days of warnings should a hurricane threaten. Their goal is a “climate-ready nation.”

Jim Carrier is a transatlantic sailor and author of The Ship and The Storm—Hurricane Mitch and the Loss of the Fantome.

Learn more about understanding weather forecasting: https://www.boatersuniversity.com/courses/weather-101-basics

August/September 2023