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Posted at 9:24 AM ET, 05/ 7/2008

Inside the Burma Cyclone

By Jason Samenow
Satellite image of Tropical Cyclone Nargis prior to landfall in Myanmar (Burma). Courtesy NOAA

As the number of dead and missing continue mounting in Burma, it's natural to wonder what kind of storm inflicted this horrible toll.

The answer is simple: A hurricane, but by another name. "Tropical Cyclone" Nargis, as the culprit storm is called, formed due to the same forces of nature that spawned the likes of Hurricanes Hugo, Andrew, and Katrina closer to home.

Keep reading for more about this storm. Also, see our full forecast through the weekend.

A "tropical cyclone" in the Indian ocean (where Nargis formed) is no different than:

  • A hurricane in the Atlantic and the Pacific east of the International Dateline (this encompasses the U.S. coasts)
  • A typhoon in the north Pacific west of the date line
  • A tropical cyclone in the Coral Sea off northeastern Australia

All of these storms begin as small clusters of thunderstorms and draw on surrounding warm, tropical ocean water to become monstrous, swirling storms often hundreds of miles across with a calm eye in the middle. These storms produce sustained winds of at least 74 mph, deadly storm surges (onshore rushes of sea) that can easily exceed 10 feet and copious amounts of rain. Tornadoes often form inside these storms when they interact with land but they generally produce damage on a smaller scale than the storm (hurricane, typhoon or cyclone) itself. The National Hurricane Center explains:

The destructive circular eyewall in hurricanes (that surrounds the calm eye) can be tens of miles across, last hours and damage structures through storm surge, rainfall-caused flooding, as well as wind impacts. Tornadoes, in contrast, tend to be a mile or smaller in diameter, last for minutes and primarily cause damage from their extreme winds.

When Nargis made landfall in Myanmar (Burma) Friday night, it had sustained winds of 130-135 mph. These winds classify Nargis as a low-end category four hurricane (out of a possible five) on the Saffir-Simpson scale, a rating of hurricane intensity.

While the 130+ mph winds were destructive, meteorologist Jeff Masters at writes the staggering casualty figures resulted mainly from Nargis' storm surge:

The ocean bottom off the coast of Myanmar [Burma] is quite shallow ... A large area of Continental Shelf waters with depth 200 meters or less extends far out to sea. This is a situation similar to the Gulf of Mexico, and is ideal for allowing large surge surge to pile up over the shallow waters. The counter-clockwise circulation of winds around Nargis likely built up a storm surge of at least 4 meters (13 feet), that then smashed ashore into the Irrawaddy Delta region, drowning thousands of people.

Relative to recent major landfalling hurricanes in the U.S., Nargis packed about the same intensity as Hurricane Hugo when it struck Charleston, S.C., in 1989. Katrina was also approximately this intensity (when it struck Louisiana) but Andrew, a rare category five hurricane, was stronger (albeit smaller in size than these other storms).

As devastating as Hugo, Andrew and Katrina were here in the U.S., the impact of Nargis on Burma has been many times more severe. Chris Mooney, the author of "Storm World" and blogger for Science Progress, in a very insightful post suggests a confluence of meteorological, socio-economic and political factors contributed to the catastrophe:

When you combine a poor population living in a low lying area in very flimsy structures with a rapidly exploding storm that took an ill-prepared region by surprise with its force--and there are already charges from Laura Bush that the military junta running Myanmar failed to warn its people--it's a perfect recipe for disaster.

All of this not to mention the government's failures in responding to this devastating storm.

The destructive qualities within a storm only mean so much. So much of the storm impact depends on societal resilience and storm preparation and response. While we are way ahead of Burma in our readiness for powerful hurricanes, our recent experience with Katrina in the U.S. reminds us we remain vulnerable as we head into what may be an active hurricane season. The importance of readiness cannot be overstated.

By Jason Samenow  | May 7, 2008; 9:24 AM ET
Categories:  International Weather, Tropical Weather  
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