8/24/2008

Hurricane Rita: The anatomy of a perfect storm

video

I dug up this NOAA satellite image of Hurricane Rita while going through some old files on my PC. It shows the rapid development of a perfect hurricane and the storm's equally rapid deterioration.

Rita formed during the horrific summer of 2005, a hurricane season unlike anything on record that produced 28 named storms. That was the summer of Hurricane Katrina, which nearly destroyed New Orleans, and Hurricane Wilma, which intensified from a tropical storm to the most powerful hurricane on record for the Atlantic Basin in barely 24 hours.

Rita became the fourth-most powerful storm on record for the Atlantic, surpassed only by Hurricane Wilma, Hurricane Gilbert (which formed in 1988) and the Labor Day Hurricane of 1935.

Rita somehow didn’t get quite the same attention as the other powerful hurricanes that formed in 2005. The hurricane lost a lot of its strength before it made landfall at the Louisiana-Texas border on September 24. But it was still a very powerful Category 3 hurricane that inflicted severe damage. Paul Trotter, a National Weather Service meteorologist in Slidell, Louisiana, told me that for a few days, Rita turned southwestern Louisiana into “a third-world country.”

It’s fascinating to watch the storm form as it crosses the Straits of Florida and then get organized and crank up as it barrels westward across the Gulf of Mexico. (You'll probably need to play the video a couple of times to see it completely.) You can see the eye just starting to form as it passes the Florida Keys on September 20. The eye is becoming distinct somewhere around the Dry Tortugas later the same day.

By September 22, when the Rita is roughly due south of Mobile Bay, the hurricane is at full roar, with sustained winds of 180 miles an hour. At this point, Hurricane Rita is pretty much a perfect storm. Its eye is tiny and well-defined, the unmistakable characteristic of a hurricane at the apex of its strength.

Had Hurricane Rita made landfall at this intensity, it would have leveled everything in its path.

But luckily, these extremely powerful storms can’t hold on to that kind of intensity very long. In fact, the mechanism of their weakening is sort of built in to their mechanics when they become this powerful. At this peak intensity, hurricanes often start going through a process known as an eye-wall replacement cycle. This means that a new eye wall starts forming around the old one. It’s sort of like Mother Nature putting a noose around the hurricane’s neck and choking it down. While this cycle is taking place, the hurricane weakens. But once the cycle is completed and the new eye wall is in place, the storm can start re-intensifying until the next replacement cycle.

As Rita takes aim at Louisiana, you can see its eye starting to cloud over and become less distinct. By the time the center of the storm touches the coast, the eye is no longer visible, an indication that the hurricane has weakened considerably from its peak intensity.

Still, there were winds of about 120 miles an hour around that indistinct eye when it came ashore.

An active hurricane season has been predicted for the rest of this summer and fall. Tropical Storm Fay – the season’s sixth named storm – has been plaguing Florida with heavy rains for a week.

September 10, considered the peak of the season, is still several weeks away.

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