Recipe for a Hurricane
Predicting how, when, and where major storms will occur can help save lives.
BY EMILY SOHN SEPTEMBER 21, 2004 SCIENCE NEWS FOR KIDS
Last August, Charley ripped through Florida. The hurricane tore up trees, wiped out houses, and
caused more than $7 billion in damage. At about the same time, a series of typhoons killed at
least 40 people in the Philippines and forced more than a million people to flee. Three weeks
later, Hurricane Frances followed Charley's lead, again pummeling Florida—to the dismay of
many people in the state. Then came Ivan and Jeanne. Hurricane Jeanne killed more than 1,000
people in Haiti, before heading for the Bahamas and Florida.
The onslaughts may have been massive, but they weren't a surprise. Every year, major storms
cause major problems around the world. There's nothing people can do to stop the powerful
forces of nature. But new techniques are helping scientists to predict how, when, and where the
big ones will occur. The more accurately scientists can give warnings, the more likely
people are to grab their valuables and flee to safety.
Predictions are improving. "We've gotten better over the years,
especially the last few years," says Phil Klotzback. He's an
atmospheric scientist at Colorado State University in Fort Collins.
Storm formation
There's plenty left to learn, though. Even when scientists can figure
out where a storm is headed, winds can change at the last minute,
This satellite image shows Hurricane
Charley near the time when the storm's
center, or eye, reached the west coast of
Florida at Cayo Costa on Aug. 13, 2004.
carrying the storm in a new direction.
Charley, for example, was originally headed right for the city of Tampa Bay but ended up hitting
the Florida coast further south.
"A little shift can make a big difference," says meteorologist Eric Blake. He works at the
National Hurricane Center in Miami. "Meteorology is both a science and an art."
The science part depends mostly on computer simulations, or models, and knowledge of the past.
Scientists have been collecting data about storms for decades. They've noticed patterns that
suggest what it takes for a strong storm to form in the
first place.
Hurricanes that hit the United States start when a
thunderstorm forms off the coast of Africa. Storms also
develop over tropical waters in other parts of the world.
Most storms end up falling apart on their own, and we
never hear about them.
For a hurricane to get organized, "conditions have to be
just right," Klotzbach says.
Hurricane-driven waves strike a sea wall.
First, the ocean water needs to be warm enough so that the
winds can take up water through evaporation, which rises
into the air. As it rises, the vapor cools and turns back into
liquid. This process releases heat. The cycle of evaporation and condensation is like an engine
that causes winds to swirl and grow. It drives the formation of a hurricane.
If wind speeds inside the swirling mass reach 40 miles per hour, the system is classified as a
"tropical storm," and it gets a name. At 75 miles per hour, it becomes a hurricane. In the western
Pacific, hurricanes are known as typhoons.
On average, 60 or 70 storms form off Africa every year, Klotzbach says. About 10 of them get
names. There are usually about six hurricanes. Two tend to be very intense, with winds of 115
miles per hour or higher.
Hurricane season lasts from June 1 to Nov. 30. Ninety percent of all hurricanes hit in August,
September, and October, Klotzbach says. Half usually happen in September, when conditions are
most favorable.
Hurricane tracks
The National Hurricane Center tracks storms as they happen. Observations and data come from
people on ships out at sea and from satellites in orbit around Earth. Computers crunch the data
for warning signs of a developing storm.
Years of observations have supplied scientists with fairly reliable patterns that help them figure
out what's going to happen next.
In the northern hemisphere, hurricanes spin
counterclockwise around a center, called an eye. Tropical
trade winds carry these systems across the ocean toward the
southeastern United States.
When a big one starts to form, meteorologists begin to watch it closely. Some experts even fly
into the eye to get a closer look. As the storm approaches land, meteorologists at the Hurricane
Center send out advisories every 6 hours. When they get to land, storms often turn north before
cruising east again, back out to sea. But with unpredictable changes in temperature and wind
patterns, it doesn't always work that way.
Experts try to predict where a hurricane will go. Here, they show Hurricane
Charley's possible track after the huge storm hit the Florida coast.
"Forecasts of the exact track have gotten considerably
better over the last 10 years," Blake says. Still, such
predictions are good for only a few hours. And storms are
constantly full of surprises.
"Storms can track in all sorts of strange ways," Klotzbach
says. Such quirks keep people glued to their radios and
TVs when hurricanes approach land, as they listen for the
latest reports on which way a storm is headed.
Future storms
Researchers can fly into the center, or eye, of a
hurricane to learn more about the storm. This
photo shows part of the wind-driven wall of clouds
surrounding the eye, a center spot of calm air.
As if that weren't tricky enough, researchers at Colorado
State try to make predictions months ahead of time. Before the start of each hurricane season,
they announce how many hurricanes and severe storms they expect will occur in the coming
summer and fall.
Some years are more active than others. And knowing what to expect
is important to lots of people, including emergency managers,
insurance companies, and people who live on the coasts. Being
prepared can save millions of dollars and lots of lives.
This sequence of satellite
images show Hurricane To predict the future, the Colorado State researchers use computer
Georges, which struck in models to look to the past. "Basically, we see what global climate
1998.
features worked well in forecasting previous years," Klotzbach says.
"We assume the future is going to be like the past."
For instance, when temperatures at the surface of the Atlantic Ocean are warm in late spring and
early summer, the hurricane season tends to be very active. In years that have a weather pattern
called El Niño, on the other hand, high winds tend to break storms up, and few hurricanes
develop.
Researchers at Colorado State have used such patterns to make predictions for the last 21 years,
Klotzbach says. Their predictions are now a lot better than those they made even a few years
ago.
Last May, for example, Klotzbach and his team predicted an "above-average" probability of
hurricanes hitting the U.S. coast in the coming hurricane season. The researchers said they
expected 14 named storms and eight hurricanes.
In fact, August had near-record storm activity, and September was also above average. For now,
the researchers expect October to be a little quieter than usual.
Personality
Although there are patterns as to when and where hurricanes occur, every hurricane is different.
Each one has its own personality.
To acknowledge that variety, every big storm gets its own
name. Storms in the Atlantic are named after people. In the
Pacific, storms can be named after flowers or take on
nicknames. The World Meteorological Organization
decides names in advance, and the alphabetical list rotates
every 6 years. Names on the list get replaced only if a
storm with a particular name is especially severe—killing
lots of people or costing loads of money. That way, the
name takes its place in history.
In 1900, a deadly hurricane struck Galveston
Island, Texas, destroying homes and killing more
than 6,000 people. It was the greatest natural
disaster in terms of loss of life in United States
history.
Teddy. Sally. Emily. Dennis. The names may sound friendly. But, watch out. Hurricanes are like
bullies. Even with a name like Debby or Charley, big storms can turn on you when you least
expect it. Knowing what to look for can help you get out before it's too late.