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Science

Hurricanes Are Moving More Slowly, Which Means More Damage (npr.org) 96

An anonymous reader shares a report: Hurricanes are moving more slowly over both land and water, and that's bad news for communities in their path. In the past 70 years, tropical cyclones around the world have slowed down 10 percent, and in some regions of the world, the change has been even more significant, according to a study published Wednesday in the journal Nature. That means storms are spending more time hanging out, battering buildings with wind and dropping more rain. "The slowdown over land is what's really going to effect people," says James Kossin, the author of the study and a tropical cyclone specialist at the National Oceanic and Atmospheric Administration. He points to Hurricane Harvey's effect on Houston as an example of what slower storms can mean for cities. "Hurricane Harvey last year was a real outlier in terms of the amount of rain it dropped," he explains. "And the amount of rain it dropped was due, almost entirely, to the fact that it moved so slowly."
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Hurricanes Are Moving More Slowly, Which Means More Damage

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  • by Oswald McWeany ( 2428506 ) on Wednesday June 06, 2018 @03:23PM (#56738496)

    More damage where they hit, but doesn't that also mean you have more time to evacuate people to get out of the path. In theory a slower moving hurricane may mean more damage but should it not mean less human fatalities? At least in places that have the financial ability to move people out the path.

    • by sqorbit ( 3387991 ) on Wednesday June 06, 2018 @03:28PM (#56738526)
      I don't know if it was just because I paid more attention, but last Hurricane season they seemed to have trouble predicting the path. They had 3 or 4 probable paths listed at once with at least one. More time should allow for that as long as we can predict where it's going to hit.
      • by ctilsie242 ( 4841247 ) on Wednesday June 06, 2018 @03:53PM (#56738704)

        This happened with Harvey. Right before it made landfall, it took a hard right for Houston, when initially, it was going to go up and pay Austin a visit.

      • by Sarten-X ( 1102295 ) on Wednesday June 06, 2018 @04:32PM (#56738950) Homepage

        That's always been the case, though. Those "3 or 4 probable paths" are the most likely out of the thousands of predictions from a dozen different models. Those models, however, have been getting more accurate [iflscience.com] over the past decade, significantly narrowing the cone of probable locations several days in advance of the storm.

        However, slower-moving storms still bring higher risk. Yes, people should have more time to evacuate, but the damage left behind will still be significantly worse, due to the increased flooding and longer duration of high wind, which in turn means more debris impacts. Those who won't (or can't) evacuate face the prospect of surviving not just a day of hiding in a shelter, but days or weeks of canned food, boiling water, and battery power... and years of work to repair the damage.

    • Comment removed (Score:5, Insightful)

      by account_deleted ( 4530225 ) on Wednesday June 06, 2018 @03:39PM (#56738598)
      Comment removed based on user account deletion
    • by ctilsie242 ( 4841247 ) on Wednesday June 06, 2018 @03:52PM (#56738696)

      Even with a slower hurricane, it can be impossible to evacuate people. Houston had a hurricane a number of years ago where people were still locked in traffic when it hit. Harvey, they didn't even bother with an evac notice because it would have just been impossible to get everyone out, so the mayor decided that sheltering in place would be better.

      • I'm not clear that Harvey was more murderous than the hurricanes of 1875 and 1886 that swept from Matagorda Bay across to Houston-Galveston. They were faster in every sense and water heights may have been higher. I lost ancestors where the water was over 30 feet deep... and I don't think it was as high with Harvey. The "unusual" 1880 storm may have been a slow one more like Harvey. Basically most of any horrific records disappeared when their town was erased, permanently.
    • by Anonymous Coward

      Not mentioned in the summary is that landfall would also decrease significantly. IFF all this is actual fact and not a whole bundle of people miscategorizing storm severity because of more expensive properties in the path and inflation, then it means the change in speed primarily shifts the damages to a tighter band of semicoastal property.

      Therefore, living mildly inland is becoming safer, but damage to islands may increase (in some cases it cannot increase because the island is already washed flat any tim

    • by Anonymous Coward

      Kind of difficult to get out of the way of a storm that covers half a state.
      It's not really feasible to evacuate the entirety of Florida, and by the time you know exactly where it will land it will be fairly close.
      And the Islands can't really evacuate anywhere and they usually catch the brunt of the storm, and have the worst infrastructure.

      • Re: (Score:2, Offtopic)

        >It's not really feasible to evacuate the entirety of Florida,

        Just because you can't, it doesn't mean you shouldn't.

        Nothing to do with hurricanes. Just empty our Florida.

        • What I don't understand: friends of mine (Austrians) recently bought a house in Florida. Almost directly on the coast. I told them that, with climate change, they'll be swimming in their living room soon enough.

          • I have the reverse story. I have relatives from the UK who got a Florida house many years ago. They recently sold it and moved their vacation residence to Portugal.
            So they won't be swimming.

    • by CohibaVancouver ( 864662 ) on Wednesday June 06, 2018 @06:14PM (#56739552)

      but doesn't that also mean you have more time to evacuate people to get out of the path

      In somewhere like Puerto Rico you don't have anywhere to evacuate the people to. Wealthy people could fly out to Florida in advance, but many in PR just had nowhere to go.

    • My understanding is that usually there's plenty of time for people to evacuate - the hard part is convincing them to actually do so. But hey, maybe more time considering the devastation being left in its wake would make a difference, especially if that devastation is far more severe than the historical average.

    • I'm not clear that Harvey was more water damaging than the hurricanes of 1875 and 1886 that swept from Matagorda Bay across to Houston-Galveston. They were faster in wind speeds and movement and the transient water heights may have been higher.

      I lost ancestors where the water was over 30 feet deep... and I don't think it was as high or higher with Harvey. The "unusual" 1880 storm may have been a slow one more like Harvey. Basically most of any horrific records disappeared when their town was erased, perm
    • by Solandri ( 704621 ) on Wednesday June 06, 2018 @09:54PM (#56740472)
      One of the deadliest hurricanes on record was Hurricane Mitch [wikipedia.org], which reached category 5 at sea. But most of its devastation happened after dropped below hurricane status. It stalled over Honduras as a tropical storm and basically flooded the country back into the stone age (75 inches of rain over roughly 2 weeks). You can't evacuate when the storm spans all the way from the Atlantic to the Pacific coast.

      The only reason it isn't the costliest Atlantic storm on record is because it hit relatively poor countries. Hurricane Harvey was a cake walk by comparison ("only" 40 inches of rain over 1 week). But Mitch was 20 years ago and doesn't quite fit the desired narrative of modern storms moving slower. So Harvey is mentioned instead.
      • 60.58 inches [npr.org]

        The highest storm total rainfall, found in Nederland, northeast of Houston. Rainfall within a tenth of an inch of that total was recorded in Groves, a neighboring community. These both exceed the previous U.S. rainfall record of 52 inches, set by Hurricane Hiki in Hawaii in 1950.

        I had to wade out of my apartment in chest-deep water during Harvey. Those 50-60 inches of rain amounts happened over 3 days, not 1 week.

    • More damage where they hit, but doesn't that also mean you have more time to evacuate people to get out of the path. In theory a slower moving hurricane may mean more damage but should it not mean less human fatalities? At least in places that have the financial ability to move people out the path.

      More damage where they hit, but doesn't that also mean you have more time to evacuate people to get out of the path. In theory a slower moving hurricane may mean more damage but should it not mean less human fatalities? At least in places that have the financial ability to move people out the path.

      The ability to move out of harm's way is a function of which economic bracket you belong to. Additionally, the slower the path, the longer you need to stay out, holed out in a motel, probably a state or two away. That costs money.

      Last hurricane season I weathered hurricane Irma holed up with my wife and kids in South Florida. My sister who lives by the coast in Melbourne, she and her husband had to get out, and it took them almost 30 hours just to get out of the state, with Irma right behind them. She wen

  • by I'm just joshin ( 633449 ) on Wednesday June 06, 2018 @03:30PM (#56738540)

    After 70 years, I expect to be moving slower too.

  • by Applehu Akbar ( 2968043 ) on Wednesday June 06, 2018 @04:13PM (#56738840)

    Very slow storms can cause devastation by increased rainfall, as Harvey did, but because hurricane damage increases exponentially with wind speed:
    http://www.aoml.noaa.gov/hrd/t... [noaa.gov] ...faster storms get increasingly dangerous more quickly with the extra wind speed that the leading quarter gets from hurricane speed added to ground speed than any "savings" from decreased time to pass by. The great New York hurricane of 1938 was only a Category 2 when it struck Long Island, but was moving unusually fast because of being squeezed between two adjacent weather systems that shot it forward like a watermelon seed. The summed wind velocity at the point of landfall made it as destructive as a Category 5.

    • When they're talking slower hurricanes, I understood that to mean the storm cell itself was traveling slower (loitering longer), and not referring to wind speeds. So an island that gets hit has hurricane winds/rain/surge for 15 hours instead of 7 hours (for example numbers pulled from air.)
      • Yes, forward motion of the stormis exactly what they are talking about. I maintain that faster net wind speeds are more dangerous than longer duration of a storm in a given place.

  • by gestalt_n_pepper ( 991155 ) on Wednesday June 06, 2018 @04:13PM (#56738844)

    We noticed already. But thanks for pointing that out.

  • by iggymanz ( 596061 ) on Wednesday June 06, 2018 @04:47PM (#56739070)

    there was no way to accurately track and measure hurricane velocity 70 years ago. through the 60s there were sporadically weather satellites each of which did not last very long. in the 70s and beyond, yes I'll believe claims of hurricane tracking/velocity

    • by flink ( 18449 ) on Wednesday June 06, 2018 @05:24PM (#56739276)

      They probably have logs of when storms made landfall at various islands as well as ships' logs to give an overall track and timeline and from there extrapolate average velocity. Also ground-based radar goes back further than the 70s, I think, so there should be some fairly accurate data that predates consistent satellite coverage (at least when the storm was over/near land).

      In addition, if you are only concerned with the storm around the time it makes landfall, then eyeballs are probably good enough. I'm sure local weather stations kept track of when the eye passed over them and how long it took to pass, which should give you the over-land velocity.

      • by Mashiki ( 184564 )

        The newest trend is to throw all that data out because it's not accurate enough. This is then followed up by using very selective samples in very small time frames, 20-30 year windows and extrapolating them over a very long time frame.

    • by pubwvj ( 1045960 )

      You're wrong. I have an ancestor who was very into meteorology, tracking winds and temperatures over 200 years ago. He also did the first air crossing of the English Channel - very avant garde - in part so he could get data. Ironically I follow in his footsteps with similar scientific bends and research today.

      Global Warming is real but it is not to blame for as much as it is being blamed for and what all too many fail to realize is not only are there losers but there are winners. Global warming in the past

      • by pubwvj ( 1045960 )

        Clarification: I meant that the person saying "70 year claim is bullshit" was wrong. They did have measurements that far back. Rereading my comment it almost looks like I'm responding to the other responder who had good points about the landfall.

        • no, they did not have hurricane tracking back then, impossible. Taking local weather measurements from points hundreds of miles apart is not tracking. Your complete ignorance is incredible.

          you are spewing without a clue

          • by pubwvj ( 1045960 )

            Wrong. Lots of people were tracking hurricanes. You need to study science history. It's very enlightening. Not everything is new.

      • nonsense, you're delusional if you think your ancestor was capable of tracking hurricanes across the ocean or anywhere else. there weren't even hurricanes where he lived!!

        • by pubwvj ( 1045960 )

          1. He lived in Boston. But you don't know enough history to be aware that I suppose. Just because he crossed the English Channel with a hot air balloon does not mean he lived in England, France or the Channel.

          2. They were tracking hurricanes. The process was a bit slower than today.

      • by dave420 ( 699308 )

        Global warming in the past didn't include human cities needing to be moved, and didn't happen nearly as quickly. Your ancestor would be appauled at your disdain for science.

        • by pubwvj ( 1045960 )

          Wow.
          You're talking to someone you don't know about something you don't know but you're so sure you're right that you take to insulting them? Or are you insulting people because you're unsure of yourself and insecure?

    • Bullshit. Before satellites, one way that comes to mind is to simply record when the eye passes over a location. Given a list of locations and times for where the eye is, you'd have a pretty good idea where the storm is moving and how fast. And this could be done with a map, reasonably accurate clocks, pen and paper, and the human version 1.0 eyeball. Granted this is a bit more difficult at sea, but tracks once landfall was made should be reasonably accurate. Accuracy could be improved further using a

  • I'm too lazy to RTFA. Can someone who did explain whether this...

    "Hurricane Harvey last year was a real outlier in terms of the amount of rain it dropped," he explains. "And the amount of rain it dropped was due, almost entirely, to the fact that it moved so slowly."

    ...means total rainfall, or just rainfall per area in the affected zone (which I presume is smaller)? i.e. Is there a certain amount of rain that a cyclone or hurricane holds and it's being distributed over a smaller area, or does the slower movement somehow increase the total water volume?

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