Typhoon Kai-Tak approaching Vietnam
Typhoon Kai-Tak was approaching Vietnam when this image was captured on October 30, 2005. The storm had maximum sustained winds of 74 knots or 85 miles per hour (1 knot = 1.15 mph), making it a Category 1 typhoon. However, it was projected to lose strength, weakening to a tropical storm, before making landfall. The storm was moving very slowly at about 5-10 kilometers per hour (3-6 miles per hour) in a Northeasterly direction. Tens of thousands of persons have already evacuated the coast in anticipation of destructive winds, storm surges, and flooding. After reaching the coast, the storm is expected to dissipate rapidly over the mountains of Vietnam. Typhoons are types of tropical cyclones and refer to those storms that form in the North Pacific; a similar storm in the North Atlantic is called a hurricane. Tropical cyclones form over the warm waters of the tropics and gain energy in the form of heat; when the storm is cut off from its heat source, it will lose energy very quickly. Air in and around mountains is often cooler than air near the ground because of the lower air pressure at higher altitudes.