It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye. If you could slice into a tropical cyclone, it would look something like this. The small red arrows show warm, moist air rising from the ocean's surface, and forming clouds in bands around the eye.
The blue arrows show how cool, dry air sinks in the eye and between the bands of clouds. The large red arrows show the rotation of the rising bands of clouds. When the winds in the rotating storm reach 39 mph, the storm is called a "tropical storm.
Tropical cyclones usually weaken when they hit land, because they are no longer being "fed" by the energy from the warm ocean waters. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.
The two GOES satellites keep their eyes on hurricanes from far above Earth's surface—22, miles above, to be exact! Learn more about this kind of orbit. These satellites, built by NASA and operated by the National Oceanic and Atmospheric Administration NOAA , save lives by helping weather forecasters predict and warn people where and when these severe storms will hit land.
Our World: What is a Hurricane? Here is a movie of Hurricane Katrina, which struck the coast of Louisiana, Alabama and Mississippi on August 29, , as a Category 3. Hurricanes may cover km miles in one day. Damage from hurricanes comes from the high winds, rainfall, and storm surge. Flooding can be devastating, especially along low-lying coastlines such as the Atlantic and Gulf Coasts.
Hurricane Camille in had a 7. Hurricanes typically last for 5 to 10 days. When a hurricane disintegrates, it is replaced with intense rains and tornadoes. There are about hurricanes around the world each year, plus many smaller tropical storms and tropical depressions. As people develop coastal regions, property damage from storms continues to rise. However, scientists are becoming better at predicting the paths of these storms and fatalities are decreasing.
There is, however, one major exception to the previous statement: Hurricane Katrina. For over a decade, the conversation in the United States over hurricanes was directed toward Hurricane Katrina. But in late October , a Category 3 hurricane called Hurricane Sandy, sometimes called Superstorm Sandy, struck the eastern coast of the United States.
What made Hurricane Sandy different from most tropical storms was how powerful it was so late in the hurricane season. The concern is that as the planet warms from anthropogenic human-enhanced climate change, the oceans will likely warm up allow hurricanes to become stronger, travel farther toward the poles, and the hurricane season last longer.
To view an interactive map on hurricanes created by the National Oceanic and Atmospheric Administration, click here.
Blizzards happen across the middle latitudes and toward the poles, usually as part of a mid-latitude cyclone. Blizzards are most common in winter, when the jet stream has traveled south and a cold, northern air mass comes into contact with a warmer, semitropical air mass. The very strong winds develop because of the pressure gradient between the low pressure storm and the higher pressure west of the storm. Snow produced by the storm gets caught in the winds and blows nearly horizontally.
Blizzards can also produce sleet or freezing rain. In winter, a continental polar air mass travels down from Canada. As the frigid air travels across one of the Great Lakes, it warms and absorbs moisture.
When the air mass reaches the leeward side of the lake, it is very unstable and it drops tremendous amounts of snow. This lake-effect snow falls on the snowiest, metropolitan areas in the United States: Buffalo and Rochester, New York. Even more insidious are the deadliest weather phenomena, a heat wave. A heat wave is different for different locations; it is a long period of hot weather, at least 86 degrees F 30 degrees C for at least three days in cooler locations but much more in hotter locations.
Heat waves have increased in frequency and duration in recent years. What do you think caused the heat wave in the image below? In the case of hurricanes that form in the Atlantic Ocean, the wind blowing westward across the Atlantic from Africa provides the necessary ingredient. As the wind passes over the ocean's surface, water evaporates turns into water vapor and rises. As it rises, the water vapor cools, and condenses back into large water droplets, forming large cumulonimbus clouds.
These clouds are just the beginning. Credit: NOAA. Meteorologists have divided the development of a tropical cyclone into four stages: Tropical disturbance, tropical depression, tropical storm, and full-fledged tropical cyclone. When the water vapor from the warm ocean condenses to form clouds, it releases its heat to the air. The warmed air rises and is pulled into the column of clouds.
Evaporation and condensation continue, building the cloud columns higher and larger. A pattern develops, with the wind circulating around a center like water going down a drain. As the moving column of air encounters more clouds, it becomes a cluster of thunderstorm clouds, called a tropical disturbance. As the thunderstorm grows higher and larger, the air at the top of the cloud column is cooling and becoming unstable. As the heat energy is released from the cooling water vapor, the air at the top of the clouds becomes warmer, making the air pressure higher and causing winds to move outward away from the high pressure area.
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