The first cyclone of the 2008 season in the northern Indian Ocean was a devastating one for Burma. According to reports from Accuweather.com, Cyclone Nargis made landfall with sustained winds of 130 mph and gusts of 150-160 mph, which is the equivalent of a strong Category 3 or minimal Category 4 hurricane. News reports stated that several thousand people have been killed, and thousands more were missing as of May 5.

Flood water can be difficult to see in photo-like satellite images, particularly when the water is muddy. This pair of images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite use a combination of visible and infrared light to make floodwaters obvious. Water is blue or nearly black, vegetation is bright green, bare ground is tan, and clouds are white or light blue.

On April 15, rivers and lakes are sharply defined against a backdrop of vegetation and fallow agricultural land. The Irrawaddy River flows south through the left-hand side of the image, splitting into numerous distributaries known as the Mouths of the Irrawaddy. The wetlands near the shore are a deep blue green. Cyclone Nargis came ashore across the Mouths of the Irrawaddy and followed the coastline northeast.

The entire coastal plain is flooded in the May 5 image. The fallow agricultural areas appear to have been especially hard hit. For example, Yangôn (population over 4 million) is almost completely surrounded by floods. Several large cities (population 100,000–500,000) are in the affected area. Muddy runoff colors the Gulf of Martaban turquoise.

The high-resolution image provided above is at MODIS’ maximum spatial resolution (level of detail) of 250 meters per pixel. The MODIS Rapid Response Team provides twice-daily images of the region in additional resolutions and formats, including photo-like natural color.

For more information: http://www.nasa.gov/topics/earth/features/nargis_floods.html

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Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Every state is at some risk from this hazard.
Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible.

Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

The following are facts about tornadoes:

• They may strike quickly, with little or no warning.
• They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.
• The average tornado moves Southwest to Northeast, but tornadoes have been known to move in any direction.
• The average forward speed of a tornado is 30 MPH, but may vary from stationary to 70 MPH.
• Tornadoes can accompany tropical storms and hurricanes as they move onto land.
  Waterspouts are tornadoes that form over water.
• Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.
• Peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer.
• Tornadoes are most likely to occur between 3 p.m. and 9 p.m., but can occur at any time.

All thunderstorms are dangerous. Every thunderstorm produces lightning. In the United States, an average of 300 people are injured and 80 people are killed each year by lightning. Although most lightning victims survive, people struck by lightning often report a variety of long-term, debilitating symptoms. Other associated dangers of thunderstorms include tornadoes, strong winds, hail, and flash flooding. Flash flooding is responsible for more fatalities more than 140 annually than any other thunderstorm associated hazard.

Dry thunderstorms that do not produce rain that reaches the ground are most prevalent in the western United States. Falling raindrops evaporate, but lightning can still reach the ground and can start wildfires.

• They may occur singly, in clusters, or in lines.
• Some of the most severe occur when a single thunderstorm affects one location for an extended time.
• Thunderstorms typically produce heavy rain for a brief period, anywhere from 30 minutes to an hour.
• Warm, humid conditions are highly favorable for thunderstorm development.
• About 10 percent of thunderstorms are classified as severe—one that produces hail at least three-quarters of an inch in diameter, has winds of 58 miles per hour or higher, or produces a tornado.

Throughout human history, there have been many threats to the security of nations. These threats have brought about large-scale losses of life, the destruction of property, widespread illness and injury, the displacement of large numbers of people, and devastating economic loss.Recent technological advances and ongoing international political unrest are components of the increased risk to national security.