Aldora Divers

August 29, 2007.

Having had Hurricane Dean pass by recently and observing all the hoopla by the media I thought it might be useful to provide another perspective.

After 16 years of living and working in Cozumel we have had plenty of opportunity to observe threats of hurricanes, near misses, minor hits… and one really serious one. It is my opinion that the real threat and concern should be much less than the media and others seem to focus on. This is especially true for those who dive Cozumel and I will try to explain.

First off, it is important to realize that hurricanes have two ways of inflicting damage. One of course is the high wind, and the other is water. Let’s discuss the wind first.

In reality, a serious hurricane is much like a large-scale tornado, usually with a tightly wound eye, around which the winds circle at high velocities. It is the wind at the eye wall that is the strongest and measured/estimated to determine the strength of the storm. Thus when the media reports that winds are sustained at 165 mph, what they call a category 5 storm, that is only at the eye wall which is frequently no more than 10 or 20 miles in diameter. The fact is that as the distance grows from the eye wall, the strength of the wind diminishes rapidly. And like a tornado, it actually takes a direct hit from the eye to inflict serious damage from the high velocity winds, at least for Cozumel. Let me give several examples.

We of course remember 2005 as the horrible storms of Wilma in Cozumel and Katrina in New Orleans. But earlier in that year we had another very strong hurricane come to Cozumel, that was Emily in July. Emily’s eye hit Cozumel as a category 4 storm, with eye wall winds of 150 mph. But the hit was to the south end of the island, which is only 20 miles south of the population center. Just 20 miles from the eye of a very serious storm—and there was virtually no damage to the town, boats, or people. Then this latest one, Dean as a category 5 storm with 165 mph sustained winds, had its eye pass within 15 miles of our State Capital, Chetumal. The city never felt winds over Force 1 strength! Then with all the worry about our beloved Cozumel, with the projections showing it coming right at us all week long—what we got was tropical storm wind and a little rain!

Oddly enough, just a few days after first writing this document, another strong hurricane is marching across the Caribbean. Despite early projections for Hurricane Felix, as of 8 am on September 3, 2007 it has sustained eye wall winds of 165 mph but it seems to be no danger to Cozumel. But graphically illustrating this important issue is that the hurricane force winds (maximum of 74 mph) extend only 30 miles from the center of the eye!

The important point of all this-- is that the destructive part of a hurricane is in reality quite narrow in width.

As for water, heavy rains associated with hurricanes do often extend great distances from the eye wall. And heavy rainfall can cause flooding. Other than an annoyance, flooding is not a factor in Cozumel as the water quickly drains off into the ocean. One of the biggest rainfall events I remember, even bigger than any hurricane was Tropical Storm Opal in 1995 which dropped 40 inches of rain in 9 hours. Any boats that did not have an active bilge pump sank and it seems to me that more boats were sunk then, than went down in Wilma. But the rain is usually well handled in Cozumel.

Then there is the rise in sea level called surge. Surge is what inflicted such catastrophic damage to New Orleans during Hurricane Katrina. The rise of nearly 12 feet breeched the levees and flooded nearly the entire city. The surge is caused by two factors: the storms lowered barometric pressure; and the wind pressure pushing water up on shallow shorelines, as most of the gulf coast has. It is a fortunate fact that islands surrounded by deep water incur only that surge caused by the lowered barometric pressure—NOT that caused by wind pressure over shallow bottoms. The reality is that even with the most severe storms the surge that can be experienced in Cozumel is just a few feet.

Waves can also be a damaging effect of a hurricane but again Cozumel is unusually lucky. The width of the channel separating Cozumel from the mainland is only 10 miles. In most cases that is not enough distance (called fetch) for waves to grow very large, no matter how strong the wind. So waves usually do little to Cozumel in even the strongest storms. But we do have to note the wave damage experienced by waterfront properties during Hurricane Wilma. Certainly an unusual storm (what must be the perfect storm) the eye of Wilma sat on Cozumel for 36 hours and the direction of circulating winds blew right down the long channel from the north, allowing waves to build to unprecedented heights. That we hope was a once in a lifetime event.

In summation, we of course prepare for the worst, as we did for Dean, but most of the time we see the Hurricanes ride up over Cuba, down to Honduras, or someplace else. Cozumel and the strong winds as we see, are quite small and it’s a very big ocean! If they do hit we all live in Concrete houses that even the big bad wolf can’t blow down.

So, when a storm is forming over 1,000 miles from Cozumel, perhaps still out in the Atlantic Ocean, and a projection is made that extends from Cuba to Honduras, the odds of it hitting any one spot with its eye wall are extremely low. That is a bet I make every year with our “hurricane insurance”, offering free diving and lodging if even the threat of a hurricane disrupts your dive days. I would never make that bet with North Storms in what is called high season! Which brings me to the final point.

I think that they have got the high and low seasons mixed up here in Cozumel. In my opinion September through October are among the best of months to dive Cozumel. The water is still warm, hotel rates are lower, the crowds are down and there are far fewer cruise ship weenies clogging the streets. And perhaps best of all there is virtually no risk of a “norte” or north storm that closes the port to diving. One January (2001?) we lost 20 out of 31 days because of that situation, and just last December there were 5 days straight that the port was entirely closed to divers. Many people never got to dive on a once a year dive trip. It is my opinion, backed up by my bet--your odds are much better in Hurricane Season.


Dave Dillehay
Aldora Divers

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