Newspaper article The Florida Times Union

During the Storm Season, All Eyes Turn to Forecasting the Most Powerful Natural Phenomenon on the Planet. HURRICANES

Newspaper article The Florida Times Union

During the Storm Season, All Eyes Turn to Forecasting the Most Powerful Natural Phenomenon on the Planet. HURRICANES

Article excerpt

A THUNDERSTORM TURNS INTO A HURRICANE

Every hurricane begins life as a tropical cyclone. A tropical cyclone with winds of 38 mph or less is called a tropical depression. When the winds reach 39 mph, it is called a tropical storm. When the winds exceed 74 mph, it's a hurricane. A tropical cylcone needs three conditions to form and strengthen into a hurricane:

A PRE-EXISTING DISTURBANCE with thunderstorms.

WARM SEAS (at least 80 degrees F) to a depth of about 150 feet.

LIGHT UPPER-LEVEL WINDS that do not change much in direction and speed throughout the depth of the atmosphere (low wind shear).

The thunderstorm's cloud tops rise higher into the atmosphere

The warm ocean waters add moisture and heat to the air, which rises, adding energy to power the storm.

Surface winds spiral into low-pressure area

THE HURRICANE GAINS DESTRUCTIVE FORCE

Warm, humid air spirals in toward eye, gaining speed toward the center.

Air sinking inside eye inhibits clouds and rain.

Winds weaken with height and air spirals outward clockwise at high altitude.

Maximum wind found in eye wall at surface

The eye is a relatively calm, clear area 20 to 40 miles across.

Surface winds spiral counter-clockwise toward the eye.

Typical hurricanes are about 300 miles wide, although they can vary considerably in size.

HURRICANE CATEGORIES

Category one: Winds 74-95 mph Category two: Winds 96-110 mph Category three: Winds 111-130 mph Category four: Winds 131-155 mph Category five: Winds greater than 155 mph

THE STORM IS STUDIED UP CLOSE

WP-3 ORION

The P3, a low-altitude NOAA aircraft, flies into hurricanes to aid scientists in better understanding the storm and improve forecasting.

RANGE: 2,559 miles low altitude, 4,409 miles high altitude

ALTITUDE: 27,000 feet

DROPSONDES

Radio transmitters attached to a parachute are dropped into the hurricane from the reconnaissance aircraft. Dropsondes measure air temperature, humidity and pressure to help calculate wind speed and direction.

THE STORM IS OBSERVED

The National Weather Service has various methods of observing a storm. Here are some of them, and where they can be used.

ALMOST ANYWHERE

SATELLITES

Geostationary Operational Environmental Satellites, orbiting the earth at 22,000 miles above the equator, can provide imagery from anywhere on the planet, every 30 minutes, day and night. With their images, forecasters can estimate the location, size, movement and intensity of a storm, and analyze its surrounding environment.

SHIPS AND BUOYS

These provide additional information about the wind speed and direction, pressure, air and sea temperature, and wave conditions within the tropical cyclone. Ships and buoys are often the only way to take direct measurements when a tropical storm is still at sea. …

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