Inside the Burma Cyclone
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 Wunderground.com 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
International Weather
, Tropical Weather
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Posted by: El Bombo | May 7, 2008 9:53 AM
Bombo: Good comments. A number of sources online rank Nargis as a Cat 4 -- although not sure there is a definitive answer. But whether it was a strong 3 or a low-end 4 is largely irrelevant given the storm's terrible effects.
Posted by: Capital Weather Gang | May 7, 2008 10:21 AM
Was the destruction increased because the winds and the cyclone eye wall were situated just right to pull in the maximum ocean surge?
Posted by: BeenThereDoneThat | May 7, 2008 10:49 AM
Beenthere: Yes--right in the Delta region as Jeff Masters described. Good observation.
Posted by: Capital Weather Gang | May 7, 2008 11:18 AM
What effect did the tide have on the storm surge's landfall? I'm not a weather expert, but I'd expect a storm making landfall at high tide to do more damage than one coming ashore when the tide was out.
Posted by: Zathras | May 7, 2008 11:57 AM
wow- what a disaster, and so sad...
Posted by: madison | May 7, 2008 12:24 PM
Having survived Hurricane Hugo, I can say for certain it was storm surge combined with poorly constructed shelters that caused the great majority of deaths. At a spot 10 miles inland and surveyed at 12 ft. above sea level, we were still in waist-deep water when the Hugo's eye made landfall - inside a brick home made in the 1950's, when homes were still built correctly. I couldn't imagine being in a mud or bamboo hut at or near sea level when a 20 ft surge comes ashore! I will say a prayer for all.
Posted by: BenJovi | May 7, 2008 1:45 PM
Zathras: Can't find historic tide data for that part of the world. A good question though.
Posted by: Capital Weather Gang | May 7, 2008 1:59 PM
Which has a greater effect on storm surge? Winds, or the low pressure? I always kind of visualized the sea surface covered with a flat balloon- the relatively higher pressure surrounding the storm pressing down, with the lower pressure in the center allowing the sea surface to bulge. The bulge comes ashore as the surge. Is there anything to this, or does the wind push the water ashore?
Posted by: CM | May 7, 2008 2:58 PM
CM: Wind -- for more see this FAQ from the National Hurricane Center.
Posted by: Jason, Capital Weather Gang | May 7, 2008 9:50 PM
Thanks Jason! I've always wondered how to quantify the pressure component of the storm surge- the link says it's only about 3 feet.
Posted by: CM | May 8, 2008 8:51 AM
boring
Posted by: bil jin | May 8, 2008 12:21 PM
i was in it im useing a frieds computer most of my famliy are dead
Posted by: kbi guyi | May 8, 2008 12:22 PM
Zathras: I learned the storm did hit at high tide ... making a bad situation much worse. Jeff Masters' at Wunderground has a new blog post which discusses this.
Posted by: Capital Weather Gang | May 8, 2008 2:31 PM
So sad ):
Posted by: Mckendry | May 16, 2008 10:10 PM
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One common characteristic of all TROPICAL cyclones. The low is a WARM-CORE system, as distinguished from the unstable COLD-CORE cyclones which generally affect us in the "Temperate" Zone.
The conditions for tropical cyclone intensification seem to be related basically to the following; (1) A warm core system or disturbance over the ocean at low latitudes which can be affected by the Coriolis force. (2) Upper-air high pressure which appears to promote outflow from the developing tropical cyclone. (3) Ocean water surface temperature of circa 26 degrees Celsius (ca. 80 F) or higher which promotes a supply of warm humid energy-rich air to fuel the developing cyclone's heat engine.
As for Nargis, the storm peaked at or near Category 3 on the Saffir/Simpson scale making it an "official" hurricane by our standards. The death toll could run as high as 60,000, considering the current "missing" figure of 45,000+. This approaches but does not quite equal the six-figure tolls historically given for Bay of Bengal cyclones which have struck India and Bangladesh over the years.
It's possible that mismanagement by the repressive Myanmar government may have enhanced the toll. An interesting note here is that both Tibet and Myanmar populations speak languages of the Tibeto-Burman family and both are currently governed by repressive regimes. The difference is that Myanmar, unlike Tibet, is being ruled by an INDIGENOUS dictatorship. (Interestingly enough, however, the Chinese support BOTH repressive regimes!!!)