Why Irma is so strong and other questions about hurricanes Winds brought by Hurricane Irma blow palm trees lining the seawall in Caibarien, Cuba, Friday, Sept. 8, 2017. (AP Photo/Desmond Boylan/Ian Brown)
Why Irma is so strong and other questions about hurricanes

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A powerful Hurricane Irma is threatening millions of people in the Caribbean and Florida. Here are answers to questions about Irma and hurricanes.


Irma is a classic Cape Verde storm, which begin near the islands off the west coast of Africa. Some of the worst hurricanes start as puffs of unstable air and storminess there and chug west. They gain strength over the warm open Atlantic. Another storm, Jose, has followed in Irma's footsteps. Some of those storms fizzle from wind shear or other weather conditions. Still others curve harmlessly north into the mid-North Atlantic and are called "fish storms." Storms also start in the Gulf of Mexico, like Katia which formed off Mexico and was declared a hurricane on Wednesday.


Hurricane season starts June 1 and ends Nov. 30. That's usually when the water is warm enough and other weather conditions are conducive to storm formation. Hurricanes need water that's at least 79 degrees (26 degrees Celsius). Peak hurricane season is from mid-August to mid-October with the peak of the peak being Sept. 10 or 11.


An average season produces 12 named storms, according to the National Weather Service. Wednesday's Katia is the 11th this season. Storms get names when winds reach 39 mph. The average season produces six hurricanes and three of those become major at 111 mph winds or higher. So far this year, there have been six hurricanes: two major ones, Harvey and Irma; two new ones Wednesday, Katia and Jose; and Franklin and Gert.


Yes. In May, the weather service predicted a 70 percent likelihood of 11 to 17 named storms with 5 to 9 becoming hurricanes. They predicted 2 to 4 major hurricanes. In early August, it was changed to a 60 percent chance of 14 to 19 named storms, 5 to 9 hurricanes and 2 to 5 major hurricanes.


Major storms can and do form back-to-back and did so last year with Matthew and Nicole, but having more than one hit the U.S. in a season is strange. If Irma hits Florida as a category 4 or 5 storm, it will be the first time in historical record that the U.S. was hit by two category 4 or 5 storms in one year, said Colorado State University meteorology professor Phil Klotzbach.


Hurricanes use warm water as fuel. Irma has been over water that is 1.2 to 1.8 degrees (0.7 to 1 degree Celsius) warmer than normal. And that warm water goes deeper than usual. High altitude winds, which can fight or even decapitate storms, are not strong, also helping Irma. While over the open Atlantic Ocean on Tuesday, Irma's 185 mph winds set a record for that region. In the entire Atlantic, Caribbean, and Gulf of Mexico, only Hurricane Allen in 1980 was stronger with 190 mph winds. Others with 185 mph winds: a 1935 Florida storm, 1988's Gilbert, and 2005's Wilma.


This is only the second time since satellite-tracking began about 40 years ago that one maintained 185 mph winds for more than 24 hours, said Klotzbach. The other was the massive killer typhoon Haiyan that killed more than 6,000 people in the Philippines in 2013.


Scientists take weeks or months to conduct intricate studies, using computer simulations, to see if a storm was worsened by man-made climate change. There have been a limited number of hurricanes since record-keeping began in 1851, which makes it difficult to do robust statistical analyses. However, scientists have long said future global warming would make some of the worst storms stronger and wetter and recently have linked climate change to future rapid intensification of storms. There's been scientific debate over whether global warming means more storms, but the stronger and wetter is generally accepted by scientists.


In the U.S., yes. Until Harvey last month, no major hurricane had hit the United States since Wilma. That 2005 storm also was the last major hurricane to hit Florida. Scientists say the 12-year landfall drought was likely chance. There were still the same number of hurricanes brewing, they just missed the United States or were not major hurricanes. During that span, Superstorm Sandy was a minor hurricane in terms of wind speed but catastrophic in damage when it hit in 2012.


Forecasters at the National Hurricane Center rely on dozens of computer simulations and their own expert experience. They use real-time readings of wind, temperature, air pressure, humidity and more. But those real-time readings are sparse and spread out. Figuring out a storm's path and strength is tricky and usually forecasts do not go out further than five days.

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Assigned 120 times
Why have predictions become more accurate?
Write your answers in the comments section below

  • Emmas-dav1
    9/13/2017 - 09:11 a.m.

    In response to "Why Irma is so strong and other questions about hurricanes". I agree that Irma was much stronger than other hurricanes. One reason I agree is because Irma lasted for more than 24 hours and went over massive land part, such as the islands and south eastern coast of America. Another reason I agree is that Irma was very strong in the wind section. In the article "Why is Irma so strong?" it states, that Irma had up to 185 mph winds threw out it's time period. A third reason i agree is because Irma killed many on the islands and destroyed amounts of houses and property, such as yards, buildings, monuments, and more. Even though Irma was strong and destructive, I know that there were worst hurricanes.

  • Meganm-dav
    9/18/2017 - 08:51 a.m.

    Why I think that hurricane predictions have become more accurate, is because of better technology. With better technology, you can see more things about a hurricane that you wouldn't know just by looking at it. You can see the wind speed, how big the hurricane and the eye is, and you can see where it might be headed. A couple of years ago, we didn't have very good technology, so we could predict very accurately where a hurricane would have hit. That's why I think technology has made predictions more accurate.

  • Quantasiaw-dav
    9/18/2017 - 01:47 p.m.

    In response to ¨Why Irma Is so strong and other questions about hurricanes,¨I think predictions become more accurate because hurricane season start June first through November the thirty (that´s when the water is warm enough).Another reason on why predictions become more accurate Is because of storm forecast.The reason I mention that was because they use real time reading of temperature, wind, air pressure, and more.

  • QMorad-dav
    9/18/2017 - 02:52 p.m.

    Wow I Agree with the scientist I agree that we are having bad hurricanes because of global warming . The United States had a hurricane drought for over 12 years of majors storm hit USA since 2005 but now that Texas had a major storm called Harvey happened a couple of weeks ago breaks the time of 12 years from a major drought of hurricanes. Data states that many hurricanes formed but passed the USA because of warm waters. Storms starts on warm water and powerful winds . I truly think the way we humans are treating the planet we are causing damage to the earth that is why all these major storms are forming .

  • CalebJ-dav
    9/18/2017 - 02:53 p.m.

    This topic is really cool because hurricanes are interesting to learn about. My opinion about this book is that this book is really good about people who do not know much about hurricanes.

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