A cyclone is an area that is surrounded by a wind system and has a low atmospheric pressure. In the southern hemisphere, the winds blow in a clockwise direction. An area that has a high atmospheric pressure and winds blowing in a counterclockwise direction is known as an anticyclone. In the northern hemisphere, a cyclone's winds blow counterclockwise and an anticyclone's winds blow clockwise.
Subtropical
cyclones are very similar to extra tropical and tropical cyclones
but unlike most cyclones, subtropical cyclones can occur at any
time of year. They are hybrid storms and it is very hard to find
consistent characteristics amoung them. The maximum wind intensity
they can have is 420 km or 300 mi from the center of the cyclone.
Subtropical cyclones have large centers, sometimes as big as 140
km in diameter. In the center there isn't much rain or pressure.
They develop from cold-upper-level polar troughs. Sometimes the
bottom portion of an upper-level trough cuts off and forms an
upper-level-cold-core low. When this reaches the surface, it becomes
a subtropical cyclone. They have a very high degree of symmetry
and have high levels of persistence. Sub-tropical cyclones don't
disappear; instead they hook on to another large storm. Many storms
become subtropical cyclones as they decline which brings about
many changes such as more rain and increased temperatures. Though
subtropical cyclones aren't dangerous by themselves, they need
to be watched in case they develop in to something more dangerous,
like a tropical cyclone.
A
typhoon is a tropical cyclone that has winds of seventy-four miles
per hour or more, and forms in the West Pacific Ocean. In order
for a typhoon to form, there are several necessary things that
must be in place. There must be warm waters, in order to fuel
the heat engine of the typhoo; an atmosphere that will cool fast
enough with height, so that it is potentially unstable to moist
convection; relatively moist layers near the mid-troposphere (3mi);
a minimum distance of at least 300 miles (500km) from the equater;
a pre-existing near-surface disturbance; and low values (less
than about 23mph [10m/s]) of vertical wind shear between the surface
and the upper troposphere. Vertical wind sphere is the magnitude
of wind change with height. Typhoons begin near the equater and
move westward, gathering intensity and size. They advance slowly,
usually at about 10 to 15 miles (16-24 km) per hour. But the circular
winds around the center are very strong, ofter reaching speeds
of 150 miles (240 km) per hour. Typhoon season runs from the first
of July through the thirtieth of November. Typhoons are always
given names when they are discovered. In the United States, we
start back at A every year. In the WesternNorthPacificBasin,
they just start where they left off last year.
The first picture is an ariel
view of a cyclone by a satillite, courtesy of www.richard-spiegel.com/.../
images/cyclone.jpg
The second picture is an ariel view
of a typhoon, courtesy of http://www.persidivista.it/sito/card/images/paesaggi/typhoon.jpg
As you can see, the two pictures are very similar.