Typhoons and hurricanes are strong tropical cyclones produced
in tropical oceans on. We called them differently because of their
different locations where they happen. In the western north Pacific,
west of International Date Line and within the scope of the South
China Sea, the tropical cyclones are called typhoons; In the Atlantic
or eastern north Pacific, tropical cyclones are called hurricanes.
That is to say, in the United States, it is hurricane, and in the
Philipines, China, Japan, it is called typhoons.
A typhoon often is accompanied by strong winds and heavy rain weather.
The wind spins counterclockwise. Isobar and isothermal are approximately
like a set of concentric circles. The central pressure is the lowest
while the temperature is the highest.
Seen from the structure of the typhoon, such a huge monster must have
unique forming conditions:
First, there should be a wide range of warm and humid atmosphere.
Bottom temperature in tropical ocean and humidity of the atmosphere
are mainly decided by temperature on the surface. The typhoon can
only form on warm ocean surface with temperature above 26 ~ 27, and
temperature of water within 60 meters deep must be higher than 26 ~27℃.
The second is the initial perturbation of the center convergence of lower
atmosphere and the high level outward diffusion. Moreover, the high-level
divergence must exceed the low-level convergence to maintain sufficient
updrafts so that the low-level disturbance can be continuously strengthened.
Thirdly, the vertical wind speed difference can not be too large. Only
when the relative motion of higher and lower air is very small can we
make the latent heat released by initial disturbance of water vapor
condensation focuse on the air column of the typhoon eye area, forming
and strengthening the typhoon center structure.
Fourth, there should be engough Coriolis force. The earth's rotation
is favorable for the formation of cyclonic vortices. The deflecting
force is close to zero near the equator, increasing toward the north
and south poles, and the typhoon takes place on the ocean about five
latitudes above the equator.
Super typhoon: the maximum average wind speed near the bottom center is
over 51.0 meters per second or level 16 or above.
Strong typhoon: the maximum average wind speed near the bottom center
is 41.5-50.9 m/s, or level 14 to 15.
Typhoon: the maximum average wind speed near the bottom center is
32.7 ~ 41.4 m/s, or level 12~13.
Strong tropical storm: the maximum average wind speed near the bottom
center is 24.5 ~ 32.6 m/s, or level 10~11.
Tropical storm: the maximum average wind speed near the bottom center
is 17.2 ~ 24.4 m/s, or 8 ~ 9.
Tropical depression: the maximum average wind speed near the bottom
center is 1.8~ 17.1 m/s, or level 6~7.