Typhoon has survived wind speed of at least 119 kilometers per hour. Cyclones that have such power tends to develop an eye (center of cyclone), the area is relatively quiet and the low atmospheric pressure in the center of circulation. Part eye of the storm often appears in satellite images as a small point, circular, and non-cloud. Part around the eye is the eye wall, the area with a width of about 16 kilometers to 80 kilometers in which the strongest thunderstorms and winds circulate around the storm center part (eye). Maximum winds persist in the strongest tropical cyclones is estimated about 314 kilometers per hour.
Japan Meteorological Agency (JMA) named tropical cyclone when it has survived the wind speed of at least 65 kilometers per hour for 10 minutes. While the Philippine Atmospheric, Geophysical, and Astronomical Services Administration provide a name for a tropical cyclone when it turned into a tropical depression in the area of the establishment at the location of 135 degrees East longitude, 115 degrees East longitude and between 5 degrees to 25 degrees North latitude. The tropical depression that successfully monitored by the American's Joint Typhoon Warning Center displayed by giving the number and spiked with the suffix "W".
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| Traces of the cyclones in Northwestern Pacific Ocean between 1980 and 2005. The vertical line on the right is the International Date Line. (Picture from: http://en.wikipedia.org/) |
Then starting in 2009, the Hong Kong Observatory started to further divide typhoon into two further classifications, namely severe typhoon and super typhoon. Severe typhoon has wind speed of at least 150 kilometers per hour, while the super typhoon has winds speed of at least 190 kilometers per hour.
Joint Typhoon Warning Center (JTWC) unofficially classifies typhoons with wind speed of at least 241 kilometers per hour (equivalent to a strong hurricane with Category 4 on the Saffir-Simpson scale) as a super typhoon.
The Northwest Pacific is an area (basin) the most active tropical cyclones on Earth compared to six other basin, the North Atlantic Ocean, the Northeast Pacific Ocean, Southwest Pacific Ocean, Southwest Indian Ocean, Southeast Indian Ocean, and the North Indian Ocean. Nearly one-third of the world's tropical cyclones form in the Northwest Pacific. Each year, an average of 25.7 tropical cyclones in this basin gets strengthening tropical storm or greater than tropical storms, and an average of 16 typhoons occur each year during the period 1968-1989. Tropical cyclone activity in the basin takes place every year, but the minimum activity occurred in February and March.
Some of the conditions necessary for the formation of hurricanes is the sea surface temperature is quite warm, atmospheric instability, high humidity in the upper troposphere and lower secondary levels, enough Coriolis force to the development of the center of low pressure, and low vertical wind shear. Normally, an ocean temperature of 26.5 degrees Celsius to a depth of at least 50 m be considered the minimum to maintain cyclonic storm class. Warm waters are necessary to maintain the center/core heat storms become hurricanes fuel system.
There are three types of lanes or tracks are common in hurricanes.
- First, the straight trail, ie westward path that affects the Philippines, southern China, Taiwan, and Vietnam.
- Second, the parabolic trail, the storm turned east and affect the Philippines, China, Taiwan, Korea, and Japan.
- Third, the north trail, the storm that followed the original direction of the north and affect only small islands.
Tropical storms in the Northwest Pacific region often hit China, Hong Kong, Japan, North Korea, South Korea, the Philippines, Taiwan and Vietnam, as well as Oceania islands areas such as Guam, Northern Mariana and Palau. Sometimes, this basin tropical storm hit Cambodia, Laos, Malaysia, Thailand and even Singapore. China's coastline is the world's most commonly affected areas of tropical cyclones.
The northeastern Philippines is the most active place on Earth for the presence of typhoons or tropical cyclones. Areas most commonly affected by tropical cyclones in the Philippines are northern Luzon and eastern Visayas. In the ten-year average of satellites that determine precipitation showed that at least 30 percent of the annual rainfall in the northern Philippines could be traced due to tropical cyclones, while the southern islands of the Philippines received less than 10 percent of the annual rainfall from tropical cyclones .
In the Philippines, the most active season since 1945 for the brunt of the typhoon or tropical cyclone was in 1993 when 19 tropical cyclones move across the country. There was only one tropical cyclone which moved through the Philippines during 1958. The Pacific typhoon season at 2004 is the busiest for Okinawa since 1957. In Guangdong, southern China, for thousands of years ago, the most active decade for typhoon occurred in 1660 and 1670's. *** [DEDE NURROSYID | PIKIRAN RAKYAT 03012013]
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