Nav: Home

Powerful hurricanes strengthen faster now than 30 years ago

May 09, 2018

Hurricanes that intensify rapidly - a characteristic of almost all powerful hurricanes - do so more strongly and quickly now than they did 30 years ago, according to a study published recently in Geophysical Research Letters, a journal of the American Geophysical Union.

While many factors are at play, the chief driver is a natural phenomenon that affects the temperature of the waters in the Atlantic where hurricanes are powering up, according to scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory and the National Oceanic and Atmospheric Administration.

They found that a climate cycle known as the Atlantic Multidecadal Oscillation or AMO is central to the increasing intensification of hurricanes, broadly affecting conditions like sea temperature that are known to influence hurricanes.

Stronger hurricanes in a day's time

Last year's lineup of powerful storms - Harvey, Irma, Jose and Maria -spurred the scientists to take a close look at the rapid intensification process. This occurs when the maximum wind speed in a hurricane goes up by at least 25 knots (28.8 miles per hour) within a 24-hour period. It's a rite of passage for nearly all major hurricanes, including the big four of 2017.

The team, comprised of Karthik Balaguru and Ruby Leung of PNNL and Greg Foltz of the NOAA, analyzed 30 years' worth of satellite hurricane data encompassing 1986 through 2015. Information came from NOAA's National Hurricane Center and the U.S. Navy's Joint Typhoon Warning Center.

Consistent with other studies, the scientists did not find that rapid intensification is happening more often nowadays.

But the scientists also looked closely at just how much the storms are strengthening. They found a sizeable jump in the strength of fast-growing storms - the storms are getting more powerful more quickly within a 24-hour period than they were 30 years ago.

The team found that the average boost in wind speed during a 24-hour intensification event is about 13 mph more than it was 30 years ago - on average about 3.8 knots (4.3 mph) for each of the three decades studied.

Several factors play a role when a hurricane gains more power rapidly, including the temperature of the surface of the ocean, humidity, characteristics of the clouds, the heat content in the ocean, and the direction of the wind at the surface compared to miles above. Among the biggest factors affecting the increase in magnitude in the last 30 years, according to the team's analysis:
  • The amount of heat available in the uppermost layer of the ocean, known as the ocean heat content. The warmer the upper ocean, the more powerful a hurricane can become.

  • Wind shear: The less the vertical wind shear - the difference in the direction and force of the winds at the surface compared to several miles into the air - the more powerful the hurricane can become.

The influence of the Atlantic Multidecadal Oscillation

The team found that the biggest factor explaining the increasingly rapid intensification is the AMO. The result comes in part from analyses using 16 separate climate models to isolate the impact from global warming.

"This was a surprise, that the AMO seems to be a bigger influence in rapid intensification than other factors, including overall warming," said Balaguru, the first author of the paper.

The AMO governs how the temperature of the waters in the North Atlantic cycles between warmer and cooler, with each period typically lasting a decade or more. The cycling occurs for reasons scientists don't completely understand, but it has broad effects on the environment. For example, it plays a big part in determining the heat content of the oceans, an important factor powering hurricanes.

The AMO has generally been "positive" - causing warmer waters - since the late 1990s.

Balaguru noted that while rapid intensification historically has occurred more often in the western Atlantic, that's not where the team found the increasing strength of the last 30 years. Rather, the phenomenon is strengthening more in the central and eastern Atlantic, especially to the east of the islands of the Lesser Antilles, which includes the Virgin Islands and Saint Kitts. That's the same area where the AMO creates warmer waters and boosts ocean heat content, in the central and eastern Atlantic.

That's exactly the alley where hurricanes Irma, Jose and Maria powered up rapidly last year. It's a proving ground of sorts where many of the most powerful hurricanes strengthen dramatically.

Balaguru notes that teasing out the effects of the AMO from broader effects of global warming was beyond the scope of the current study but is a focus for scientists.
-end-
The work was supported by the Department of Energy's Office of Science.

DOE/Pacific Northwest National Laboratory

Related Hurricane Articles:

Hurricane resilience in the Bahamas
A new Stanford-led study provides information on how to invest in natural coastal ecosystems that the Bahamian government, community leaders and development banks are applying in post-disaster recovery and future storm preparation in the Bahamas.
NASA finds a weaker hurricane Juliette
Hurricane Juliette has been weakening and NASA-NOAA's Suomi NPP satellite provided a look at the strength of storms within.
NASA sees Dorian become a hurricane
NASA's Terra satellite passed over the northwestern Atlantic Ocean as Dorian reached hurricane status during the afternoon of August 28, 2019.
Landslides triggered by Hurricane Maria
Hurricane Maria hit the island of Puerto Rico on 20 September 2017 and triggered more than 40,000 landslides in at least three-fourths of Puerto Rico's 78 municipalities.
NASA sees Atlantic's Leslie become a hurricane
NASA's Aqua satellite captured an infrared image of Hurricane Leslie that revealed strong storms circled the center.
NASA sees Walaka becoming a powerful Hurricane
The Global Precipitation Measurement mission or GPM core satellite passed over the Central Pacific Hurricane Center and analyzed Walaka's rainfall and cloud structure as it was strengthening into a hurricane.
NASA finds a weaker Hurricane Olivia
Infrared data from NASA's Terra satellite revealed that the area of coldest cloud topped thunderstorms has dropped from the previous day, indicating weaker uplift and less-strong storms
NASA looks at heavy rainmaker in Hurricane Lane
Cloud top temperatures provide scientists with an understanding of the power of a tropical cyclone.
Hector weakens but remains Category 4 Hurricane
Hurricane Hector has weakened slightly but still remains a robust Category Four storm at present.
UA forecast: Below-average hurricane activity
The UA hurricane forecasting model, which has proved to be extremely accurate over the years, is calling for fewer hurricanes in the Atlantic this year on the heels of a devastating 2017.
More Hurricane News and Hurricane Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#566 Is Your Gut Leaking?
This week we're busting the human gut wide open with Dr. Alessio Fasano from the Center for Celiac Research and Treatment at Massachusetts General Hospital. Join host Anika Hazra for our discussion separating fact from fiction on the controversial topic of leaky gut syndrome. We cover everything from what causes a leaky gut to interpreting the results of a gut microbiome test! Related links: Center for Celiac Research and Treatment website and their YouTube channel
Now Playing: Radiolab

The Flag and the Fury
How do you actually make change in the world? For 126 years, Mississippi has had the Confederate battle flag on their state flag, and they were the last state in the nation where that emblem remained "officially" flying.  A few days ago, that flag came down. A few days before that, it coming down would have seemed impossible. We dive into the story behind this de-flagging: a journey involving a clash of histories, designs, families, and even cheerleading. This show is a collaboration with OSM Audio. Kiese Laymon's memoir Heavy is here. And the Hospitality Flag webpage is here.