This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Wednesday, May 15, 2013

Cyclone Mahasen, Gravity Waves, and Imminent Humanitarian Disaster

Projected path of Cyclone Mahasen as of May 14, 2013
Bearing in mind that hurricane, cyclone and typhoon are all words for big cyclonic storms, Cyclone Mahasen bearing down on Bangladesh, Myanmar (formely Burma) and possibly northeast India depending on its trajectory. The low-lying areas poses a flooding threat to millions of people, some estimates being as many as 8.2 million. Particularly at risk are about 140,000 living in makeshift quarters in low-lying camps. The cyclone has weakened to a Category 1 tropical storm rather than a cyclone, but the large extent of low-lying areas in Bangladesh poses a major problem with wind, rain (up to 500 mm), tidal surge and waves in the forecast.
     Mahasen is being pushed to the northeast by a trough of low pressure. There are heavy thunderstorms, largely out over water around the southeastern coast of India. MODIS images on NASA's Terra satellite showed that (as of May 14) it was a tightly wound, compact storm with strong convection around the storm center. it is moving about 8 mph to the northeast (as of May 14). Sea surface temperatures in the Bay of Bengal are near 84-86 F, warm enough to support the tropical cyclone, and vertical wind shear is minimal, allowing the storm to potentially strengthen.
     NASA has released an image (lower right) on which someone has sketched atmosppheric gravity waves traveling out from the center of the storm. This suggests that the core of Mahasen extends up into the stratosphere. Gravity waves transfer the momentum from the stratosphere back down into the troposphere as the system seeks to regain density equilibrium.
Gravity waves (marked with circle and arcs) from
Cyclone Mahasen NASA image
       This storm illustrates a potentially tragic intersection of earth processes and human affairs. A stateless Muslim minority, the Rohingya, was created when sectrian violence erupted between Buddhists and Muslims last year. The Rohingya suffered during decades of military rule in Myanmar, and they have been forced to live in camps in the low lying areas of these countries. The Rohingya are reluctant to leave the camps because they distrust the security forces involved, say United Nations spokesmen. Already a boat ferrying people from one camp in Rakhine (a state in Myanmar) to safer areas has capsized with 58 people still missing from the accident. Authorities are well organized for the storm preparation, having been subjected to repeated cyclones. In 1970 Cyclone Bhola killed an estimated 400,000 people. Landfall is expected Thursday or Friday morning near Chittagong, Bangladesh, which may spare the restive state of Rakhine from its full impact.

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