Atmospheric Tricks and Treats

“Getting up the South Atlantic is quite tricky,” says Cahalan, “even under normal circumstances. The winds just aren’t favorable for sailing northward there. Ken Campbell, the Director of Marine Services at Commander’s Weather, agrees. “When the Cheyenne got to the Falkland Islands, we had to make a decision about how to go north in the South Atlantic. The forecasts were very uncertain, so we decided to be conservative, to just pick the shortest distance and look for little favorable wind shifts up close.”

The winds, however, were anything but favorable. After pushing their way north for thousands of kilometers, they finally reached the latitudes where they should have been able to pick up the southeast trade winds to hurry them back to the equator. But when they got close, the trade winds weren’t there.

“This is where things got really interesting for us,” says Cahalan. “At this point, we are up essentially 24 hours a day, sleeping in 2-hour shifts, just watching the weather, speaking with Commander’s Weather several times a day, trying to find some favorable winds. We had already done a lot of damage to the mast track and sails just from being at sea for so long, and then we began to see squall activity on the horizon—really big clouds ahead. Also, the seaway turned very bad, very choppy, even though there was little wind. So we began to know something was going on ahead.”

The crew of Cheyenne worked continuously to keep the catamaran moving at top speed. (Photograph copyright Nick Leggatt)

Back in New Hampshire, the forecasters at Commander’s Weather were using satellite imagery and other weather information to figure out how to get the Cheyenne back to the equator without the trade winds. “Once we got to about 30 south,” explains Campbell, “we saw a big area of squalls, and of course we didn’t want them to go in the middle of that. So we had to send them around to the west.”

Damage to Cheyenne after more than a month at sea forced the crew to make repairs under sail. Wary of further damage, the crew had to navigate carefully to avoid high winds. (Photograph copyright Nick Leggatt)

As Cheyenne went west, the squalls to the northeast seemed to be coalescing into a single system. When air is swept high into the atmosphere by thunderstorms, the air pressure at the surface can drop significantly, at least temporarily. Surrounding, higher-pressure air flows into the low pressure core to even things out.

“This effort to balance things out is what normally drives the trade winds—high pressure at the horse latitudes causes air to move toward the equator, where daily thunderstorms create a band of low pressure,” explains Campbell. “But that storm created a large area of low pressure [to the south], so there were no trade winds. We were left in a void.”

Cahalan recalls the updates coming in from Commander’s Weather as the situation with the developing low was changing very quickly. “The forecasters were initially saying, ‘Oh, yeah, by the way, as you know there is a little low out there you’ll have to steer clear of,’ and then it was,‘ Hmm, well, we are seeing some really strong winds,’ and then it was, ‘Wow, it’s spinning pretty good.’,” says Cahalan with a laugh. “Because we had always known it was there and had gone around it, we were far enough west of the storm that we weren’t in any immediate danger from it, but without the trade winds, we were having a hard time getting north.”

Skirting Catarina

Not everyone was as lucky as the crew of the Cheyenne. Paying no attention to the fact that it was not in “hurricane territory,” between March 20-26, the storm developed a hurricane-looking eye, hurricane-looking clouds, and finally, hurricane-force winds of 92 mph. The storm plowed ashore in the state of Santa Catarina in southern Brazil, killing several people, damaging many vessels in the Brazilian fishing fleet, and destroying thousands of houses.

Although the Cheyenne wasn’t in any immediate danger from the storm that Brazilians eventually named “Catarina,” their world-record pace record was. With the storm interfering with the trade winds, Cheyenne continued to struggle to make northward progress.

From March 22 to March 26, 2004, a low-pressure system off the coast of Brazil evolved from a line of squalls into an organized storm with hurricane-force winds. (GOES images courtesy NOAA NESDIS Satellite Services Division)

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“Finally,” says Cahalan, “we got a break.” At the core of all tropical storms is an area of low air pressure. Air from hundreds, even thousands, of kilometers around flows toward the low-pressure core of the storm. “In the Southern Hemisphere air moves in a clockwise direction around a low,” explains Cahalan. “Since we were west of the storm, we got pushed along by the southerly winds coming around the bottom of the low. We finally picked up the trade winds at about 15 degrees.”

Swept along by winds spiraling into Catarina’s low-pressure center, Cheyenne crossed into the steady trade winds on March 24. (Image courtesy NASA/JPL Seaflux)

Cheyenne re-crossed the equator on Day 50, and left the tropics behind. “We had a fast ride through the northeast trades and then were fortunate to meet southerly winds associated with an approaching low-pressure system at 20 degrees North.” They rode the coattails of that winter storm almost all the way back to the starting line in the English Channel. After 58 days and nine hours, they arrived where they had begun, beating the previous record by just over five days.

 Storm Speculation: Hurricane or Not?
 The Race is On

Editor’s note: Alas for the crew of the Cheyenne, records are made to be broken. In March 2005, the Orange II and its crew set a new round-the-world record -- with their time of 50 days, 16 hours, 20 minutes, and 4 seconds.