[00:00.00]Three powerful ocean storms threaten the Caribbean, the coast of the southeastern United States and southeastern Mexico.
[00:10.49]Hurricane Irma has struck Cuba and now threatens the state of Florida with strong winds and rain.
[00:19.34]The storm has caused deaths and widespread destruction on several Caribbean islands.
[00:27.34]Hurricane Katia is in the southern Gulf of Mexico.
[00:31.85]It is nearing Mexico’s eastern coast.
[00:35.68]And Hurricane Jose is gaining strength in the Atlantic Ocean.
[00:41.43]The three hurricanes come as the state of Texas recovers from Hurricane Harvey.
[00:47.94]The huge storm caused severe flooding and billions of dollars in damage in Houston, the country’s fourth-largest city.
[00:58.83]Hurricane season in the Atlantic Ocean goes from June 1 to November 30.
[01:06.06]And the month of September is the peak of storm activity.
[01:11.50]Hurricanes are the most powerful storms in the Earth’s atmosphere.
[01:18.05]The storms have different names depending on where they take place.
[01:24.62]Scientists call all these storms tropical cyclones.
[01:29.45]If the storms form over the Atlantic Ocean or eastern Pacific Ocean, they are called hurricanes.
[01:38.69]Storms that form in the western Pacific Ocean are known as typhoons.
[01:45.71]In the Indian Ocean, they are called cyclones.
[01:50.31]Although they have different names, all these storms form in the same way.
[01:57.92]Scientists at the American space agency NASA describe tropical cyclones as huge weather “engines” that use warm, moist air as fuel.
[02:14.48]They can only form over warm, tropical waters near the equator.
[02:21.25]A tropical cyclone develops when warm moist air near the surface of the ocean rises.
[02:30.69]This creates an area of unusually low air pressure.
[02:35.62]Higher-pressure air from surrounding areas pushes in to take the place of the warm, rising air.
[02:44.80]It becomes warmer and moister and rises, too.
[02:49.47]The rising, moist air goes high into the atmosphere, where temperatures are low.
[02:57.32]This creates wind. The moisture forms clouds.
[03:03.32]The developing weather system begins to spin because of the Earth’s rotation.
[03:10.01]As the storm spins faster and faster, what is called an “eye” of the storm develops at its center.
[03:19.85]This is a calm area of very low pressure. Higher pressure air from above flows down into the eye.
[03:31.63]When wind speeds reach about 63 kilometers per hour, meteorologists say a tropical storm has formed.
[03:42.89]When winds in the storm are measured at 119 kilometers per hour or above, a tropical storm officially becomes a category one “tropical cyclone,” or in the Western Hemisphere, a hurricane.
[04:02.95]Meteorologists use measurements of wind speed to place tropical cyclones in categories.
[04:12.17]When a hurricane’s wind speed reaches 155 kilometers an hour, it is called category two.
[04:21.94]The categories go up to category five, the most dangerous and catastrophic storm.
[04:31.04]A category-five storm has wind speeds measured at over 250 kilometers per hour.
[04:40.55]They can cause a storm surge, or a rise in water levels of more than five meters.
[04:49.93]The National Oceanic and Atmospheric Administration, or NOAA, operates two satellites that track weather and storms in the eastern Pacific and Atlantic Oceans.
[05:05.44]NOAA provides maps from the (GOES) satellites online.
[05:11.39]I’m Mario Ritter.