Heavy rains in Thailand during September and October have led to extreme flooding that has killed 283 people and caused that nation’s most expensive natural disaster in history. On Tuesday, Thailand’s finance minister put the damage from the floods at $3.9 billion. This makes the floods of 2011 the most expensive disaster in Thai history, surpassing the $1.3 billion price tag of the November 27, 1993 flood, according to the Centre for Research on the Epidemiology of Disasters (CRED). Floodwaters have swamped fields and cities in 61 of Thailand’s 77 provinces, affected 8.2 million people, and damaged approximately 10% of the nation’s rice crop. Thailand is the world’s largest exporter of rice, so the disaster may put further upward pressure on world food prices, which are already at the highest levels since the late 1970s. Some of the highest tides of the month occur this weekend in the capital of Bangkok, and the additional pressure that incoming salt water puts on the flood walls protecting the city is a major concern. A moderate monsoon flow continues over Southeast Asia, and the latest GFS model precipitation forecastforesees an additional 2 – 5 inches of rain over most of Thailand during the next three days.
Figure 1. Thailand’s Chao Phraya River forms at the confluence of smaller rivers near Nakhon Sawan and flows past Bangkok to the Gulf of Thailand. Floodwalls meant to contain the river collapsed in downtown Nakhon Sawan, the Bangkok Post reported on October 11, 2011. The aftermath of the burst floodwalls left the city looking like a lake. As rivers overflowed in Thailand, the Tônlé Sab (Tonle Sap) lake in neighboring Cambodia (lower right of images) overflowed. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these images on October 11, 2011, and October 8, 2010. These images use a combination of visible and infrared light to better distinguish between water and land. Vegetation is green, and clouds are pale blue-green. Water is dark blue. In 2011, water rests on floodplains between Phitsanulok and Nakhon Sawan. Image credit: NASA.

Heavy rains due to an active monsoon and moisture from tropical cyclones
Rainfall in September peaked at 574.3mm (22.61″) at Nong Kai in Northeastern Thailand, 501mm (19.72″) at Uttardit in Northern Thailand, and 1446.7mm (56.96″) in Eastern Thailand. For these regions, precipitation averaged 40 – 46% above normal in September. In the week ending Oct. 13, an additional 4 – 8″ fell in Central and Thailand, where the capital of Bangkok lies. On Thursday, 38 mm (1.53″) fell in Bangkok, and rainfall amounts of 1 – 3″ fell over much of Central Thailand. Heavy monsoon rains are common in Thailand and Southeast Asia during La Niña events, and we currently have a weak La Niña event occurring. Ocean temperatures in the waters surrounding Thailand during September and October have been approximately 0.3°C above average, which has increased rainfall amounts by putting more water vapor into the air. The remains of Tropical Storm Haitang and Typhoon Nesat also brought heavy rains in late September. The flooding has also affected neighboring Cambodia, killing at least 183 people. Floods have also killed 18 in Vietnam and 30 in Laos this fall.

The Atlantic.com has some remarkable photos of the flooding in Thailand.

Figure 2. Top ten most expensive natural disasters in Thailand since 1900, as tabulated by the Centre for Research on the Epidemiology of Disasters (CRED).

Hurricane Jova kills five in Mexico, but damage limited
Hurricane Jova killed five people in Mexico but damage was less than expected, amounting to less than $52 million, according to AIR-Worldwide. Jova hit the Pacific coast of Mexico Tuesday night as a Category 2 hurricane with 100 mph winds. Wunderblogger Mike Theiss rode out the storm on the coast, and has a a great post on his experience, which I excerpt here: “the winds suddenly picked up fiercely and started pounding the building I took shelter in. The surf ran way up on the beach and the waves were pounding the buildings and spraying up over everything at the pool. The wind was screaming and howling and the glass was flying. The Spanish tiles were getting ripped off the roof and all the glass light fixture were popping like balloons.”

Figure 3. Mudslide from Hurricane Jova covers a road near Mazanillo, Mexico. Image credit: Mike Theiss.

Invest 94L in the Atlantic no threat
An area of disturbed weather (Invest 94L) between North Carolina and Bermuda is moving quickly to the northeast at 15 – 20 mph. This system has a modest amount of heavy thunderstorm activity and a the beginnings of a surface circulation, as seen on recent visible satellite imagery. Conditions are marginal for this to develop into a tropical depression, as wind shear is a high 20 – 30 knots, and ocean temperatures are at the lower limit for develoment, 26.5°C (80°F.) NHC is giving 94L a 20% chance of developing.

Western Caribbean disturbance
In the Western Caribbean, a large area of disturbed weather associated with a low pressure system has developed. Moisture from Tropical Depression 12-E, which moved inland near the Mexico/Guatemala border and dissipated on Wednesday, is invigorating the Western Caribbean low. Heavy rains from the low are affecting much of Central America, Cuba, and Mexico’s Yucatan Peninsula, and these rains will probably intensify over the weekend as the low moves slowly northwest and gradually develops. The low is too large to develop quickly, and NHC is giving the system just a 20% chance of developing into a tropical depression by Sunday. Most of the models predict only weak development of the storm, since wind shear is currently a high 20 – 25 knots, and is expected to be in the moderate to high range, 15 – 25 knots, over the next threee days. Rains from the storm are already affecting the Florida Keys, as seen on long-range Key West radar. A personal weather station on Grand Cayman Island has picked up 0.87″ of rain so far this morning from the storm. Mexico’s Yucatan Peninsula and Western Cuba will see the heaviest rains from the disturbance over the weekend, and South Florida could see heavy rains of 2 – 4 inches on Sunday and Monday.

Jeff Masters