AIR Notes Nargis Showed ‘Unusually Warm Sea-Surface Temperatures’

May 12, 2008

Boston-based AIR Worldwide’s analysis of Nargis, the deadly tropical cyclone, which struck Myanmar’s (Burma’s) densely populated Irrawaddy River Delta region (See IJ web site –, notes that powerful storms in the area have been increasing over the years.

“The North Indian Ocean generates about four tropical cyclones each year,” explained Dr. Peter Sousounis, senior research scientist at AIR Worldwide. “But, over the last 30 years, there has been a significant increase in the number of Category 4 and 5 storms (Saffir-Simpson Scale).

“For example, during the period 1975-1989, there was only one such storm, representing 8 percent of the total number of tropical cyclones during that period. During the subsequent 15-year period (1990-2004), there have been seven such storms, or 25 percent of the total. Last year alone saw two such intense storms.”

He then noted that “sea-surface temperatures in the North Indian Ocean have increased about 0.4°C [0.72° F] over the last 30 years. This year, water temperatures in the Bay of Bengal during the last week of April, when Nargis was forming, were already over 30°C [86°F], about one degree warmer than normal.”

In addition to the rain and wind, AIR noted, “a12-foot storm surge inundated 50 percent of low-lying homes in an area occupied by nearly 2.5 million people.

“Nargis first developed on April 27 as an area of deep convection over the Bay of Bengal. Under the influence of high pressure centered to the northwest, it tracked northwest along the high’s periphery, developing slowly. Nargis was initially expected to make landfall somewhere in southeast India or Bangladesh. It stalled on April 28 due to high pressure from the southeast,” causing it to weaken.

“As the southern high took over, Nargis resumed its motion, Dr. Sousounis continued. “On May 1st, a trough approached from the west and the storm began to re-intensify, taking a more northeasterly track. Nargis finally made landfall around 12:00 UTC with maximum sustained winds of 127 mph and a radius of maximum winds of approximately 33 miles. It passed just north of Yangon [Rangoon] with winds of 80 mph [128 kph].”

Source: AIR Worldwide –

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