What is a hurricane?
It is a powerful, spiral weather that result from low pressure systems. (low pressure
systems explained below) It is seen as a massive storm (powerful winds often with rains,
thunderstorms and lightning) that usually moves, covering a stretch of 500-600miles.
Low Pressure System
This is an area (over land or water) where the atmospheric pressure is lower than that of the area
surrounding it. Typically, there are winds around, and the air is a lot warmer, causing atmospheric
lifting. Low pressure systems result in cloud formation and bad weather. Hurricanes, typhoons,
tropical storms and tropical depressions are all examples of low pressure systems.
The sustained winds within the hurricane move with speeds of over 74miles per hour
(that is about the speed at which cars move on the highway), but the entire storm
body moves at about 10-20 miles per hour. They often carry torrential rains and can
bring about floods and landslides. Note that flooding along coastal regions is not only
as a result of the rains, but more as a result of storm surges. Hurricanes can last for
over a week.
How do hurricanes form?
Hurricanes only form on warm ocean waters of about 80°F. This is why it is common
in the tropics where temperatures are high all year round. Hurricanes also need wind
action to form. Now here is the fun part
Warm air, together with moisture from evaporation from the ocean surface rises,
creating low pressure on the water surface, which is immediately replaced by cooler
air. This process continues, and the resulting moisture-laden clouds begin to expand.
Thunderstorms with rains form.
The thunderstorms with rains begin to move slowly with mild western winds (too
much winds will disperse the buildup). In a day or two, stronger vertical currents
build up over the ocean surface upward. More warm air rises and the winds begin to
move in circular manner, caused by the earth’s rotation. The rising warm air causes
pressure to decrease at higher altitudes. The entire system is now in circular motion
around a central point. This is called a tropical depressionand they have a wind
speeds going up to about 38 miles per hour.
In a couple of days, as the system moves over more warmer waters, the clouds
expand even more, and the winds begin to speed up. Gale force winds, thunderstorms
and heavy rains are in full force at this point. This may be called a tropical storm, and
they have wind speeds up to 74miles per hour.
Continuing its movement westward, the tropical storm may be moving over even
warmer waters. The energy from the warm ocean, in the form of very warm air rising
and the gushing of cooler air replacing it throws the entire storm into a fury of
powerful, huge and monstrous spiral storm that can be seen from space. The spiral
has a calm center called the eye.
The eye, is surrounded by a towering and extremely dangerous vertical movement of
thunderstorms. This is called the eye wall. The winds of the eye wall is so powerful
that it spins and carries huge amounts of ocean water as it moves ashore.
The hurricane has now made a landfall (has reached land). With winds over 74mph to
about 160mph, massive destruction is usually inevitable. As the system is no more
over water, its' fuel has run out and begins to ease out. The winds will subside and
eventually end, but the rains may continue.
Hurricane measurement and classification
Hurricane winds are measured using the Saffir-Simpson Hurricanescale. This scale
was first developed in the late 1960s and was further developed in the early 1970s. It
uses measurements in pressure, wind speed, storm surge and damage potential to put
hurricanes into 5 categories.
Impact
storm surges. Destruction, electric, nuclear... bring winds, floods.
hurricanes names
The World Meteorological Organization has assigned 21 names, in alphabetical
order, for each years’ hurricane season. In fact, the names are given to tropical
storms, and they keep the name as they develop into hurricanes. Usually, there are
less than 21 tropical storms in each region's hurricane season.
Some most destructive hurricanes
Katrina:
Early in the morning on August 29, 2005, Hurricane Katrina
struck the Gulf Coast of the United States. When the storm made
landfall, it had a Category 3 rating on the Saffir-Simpson
Hurricane Scale–it brought sustained winds of 100–140 miles per
hour–and stretched some 400 miles across. The storm itself did a
great deal of damage, but its aftermath was catastrophic. Levee
breaches led to massive flooding, and many people charged that
the federal government was slow to meet the needs of the people
affected by the storm. Hundreds
of
thousands of people in
Louisiana, Mississippi and
Alabama were displaced from
their homes, and experts estimate that Katrina caused more than
$100 billion in damage.
During the past century,
hurricanes have flooded
New Orleans six times:
in 1915, 1940, 1947,
1965, 1969 and 2005.
Irene:
Hurricane Irene
August 20-29, 2011
Irene first struck the U.S. as a Category 1 hurricane in eastern North Carolina, then moved
northward along the Mid-Atlantic Coast. Wind damage in coastal North Carolina, Virginia, and
Maryland was moderate, with considerable damage resulting from falling trees and power lines.
Irene made its final landfall as a tropical storm in the New York City area and dropped torrential
rainfall in the Northeast that caused widespread flooding. More than 7 million homes and
businesses lost power during the storm, and Irene caused at least 45 deaths and more than $7.3
billion in damages.
Irene was the first hurricane to hit the U.S. since Ike in September 2008 and was the most
significant tropical system to make a direct landfall in the Northeast since Hurricane Bob in 1991.
Hurricane Irene is an example of increasing accuracy in forecasting storm track. Its landfall in
eastern North Carolina and path northward were accurately predicted more than four days in
advance by NOAA’s National Hurricane Center, which used information from weather satellites,
hurricane models, aircraft observations, and other data. NOAA’s delivery of critical environmental
forecasts provided essential advance information that allowed emergency officials to plan necessary
evacuations and sparked individuals to take safety precautions.
Prevention and prediction:
Weather forecasters can predict an huracain measuring preassure, humidity,
temperature... Cities can be evacuated if a huracaine is predicted to come. If not, the
safest to do is going to a basement, somewhere underneath the ground.
Sources:
http://eschooltoday.com/natural-disasters/hurricanes/what-is-a-hurricane.html