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A28 SCIENCE
Friday 8 September 2017

Why Irma is so strong and other questions about hurricanes

By SETH BORENSTEIN tists have long said future
AP Science Writer global warming would
WASHINGTON (AP) — A make some of the worst
powerful Hurricane Irma is storms stronger and wetter
threatening millions of peo- and recently have linked
ple in the Caribbean and climate change to future
Florida. Some answers to rapid intensification of
questions about Irma and storms.
hurricanes: There’s been scientific de-
WHERE DO THESE STORMS bate over whether glob-
COME FROM? al warming means more
Irma is a classic Cape storms, but the stronger
Verde storm, which be- and wetter is generally ac-
gin near the islands off the cepted by scientists.
west coast of Africa. Some WASN’T THERE A HURRICANE
of the worst hurricanes start DROUGHT?
as puffs of unstable air and In the U.S., yes. Until Harvey
storminess there and chug last month, no major hur-
west, gaining strength over ricane had hit the United
the warm open Atlantic. States since Wilma.
Another storm, Jose, has That 2005 storm also was
followed in Irma’s footsteps. the last major hurricane to
Some of those storms fizzle hit Florida. Scientists say the
from wind shear or other This Sept. 6, 2017 photo provided by the Dutch Defense Ministry shows a few of the homes that 12-year landfall drought
weather conditions. Still remained intact in the aftermath of Hurricane Irma, in St. Maarten. was likely chance.
others curve harmlessly Associated Press There were still the same
north into the mid-North At- or higher. So far this year, gy professor Phil Klotzbach. HOW UNUSUAL IS IRMA? number of hurricanes brew-
lantic and are called “fish there have been six hur- WHY IS IRMA SO STRONG? This is only the second time ing, they just missed the
storms.” Storms also start in ricanes: two major ones, Hurricanes use warm water since satellite-tracking be- United States or were not
the Gulf of Mexico, like Ka- Harvey and Irma; two new as fuel. Irma has been over gan about 40 years ago major hurricanes. During
tia which formed off Mex- ones Wednesday, Katia water that is 1.2 to 1.8 de- that one maintained 185 that span, Superstorm San-
ico and was declared a and Jose; and Franklin and grees (0.7 to 1 degree Cel- mph winds for more than dy was a minor hurricane
hurricane on Wednesday. Gert. sius) warmer than normal. 24 hours, said Klotzbach. in terms of wind speed but
WHY ARE STORMS HAPPEN- DID FORECASTERS SEE THIS And that warm water goes The other was the mas- catastrophic in damage
ING NOW? BUSY YEAR COMING? deeper than usual. High sive killer typhoon Haiyan when it hit in 2012.
Hurricane season starts Yes. In May, the weather altitude winds, which can that killed more than 6,000 HOW ARE STORMS FORE-
June 1 and ends Nov. 30. service predicted a 70 per- fight or even decapitate people in the Philippines in CAST?
That’s usually when the cent likelihood of 11 to 17 storms, are not strong, also 2013. Forecasters at the National
water is warm enough and named storms with 5 to 9 helping Irma. IS THIS GLOBAL WARMING? Hurricane Center rely on
other weather conditions becoming hurricanes. While over the open At- Scientists take weeks or dozens of computer simu-
are conducive to storm for- They predicted 2 to 4 ma- lantic Ocean on Tuesday, months to conduct intricate lations and their own ex-
mation. Hurricanes need jor hurricanes. In early Au- Irma’s 185 mph winds set studies, using computer pert experience. They use
water that’s at least 79 de- gust, it was changed to a a record for that region. In simulations, to see if a storm real-time readings of wind,
grees (26 degrees Celsius). 60 percent chance of 14 the entire Atlantic, Carib- was worsened by man- temperature, air pressure,
Peak hurricane season is to 19 named storms, 5 to 9 bean, and Gulf of Mexico, made climate change. humidity and more.
from mid-August to mid- hurricanes and 2 to 5 major only Hurricane Allen in 1980 There have been a limited But those real-time read-
October with the peak of hurricanes. was stronger with 190 mph number of hurricanes since ings are sparse and spread
the peak being Sept. 10 or ARE BACK-TO-BACK BIG winds. record-keeping began in out. Figuring out a storm’s
11. HURRICANES UNUSUAL? Others with 185 mph winds: 1851, which makes it diffi- path and strength is tricky
WHAT’S AN AVERAGE SEA- Major storms can and do a 1935 Florida storm, 1988’s cult to do robust statistical and usually forecasts do go
SON LIKE? form back-to-back and Gilbert, and 2005’s Wilma. analyses. However, scien- out farther than five days.q
An average season pro- did so last year with Mat-
duces 12 named storms, thew and Nicole, but hav-
according to the National ing more than one hit the
Weather Service. Wednes- U.S. in a season is strange.
day’s Katia is the 11th this If Irma hits Florida as a cat-
season. Storms get names egory 4 or 5 storm, it will be
when winds reach 39 mph. the first time in historical re-
The average season pro- cord that the U.S. was hit by
duces six hurricanes and two category 4 or 5 storms
three of those become in one year, said Colorado
major at 111 mph winds State University meteorolo-