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Hurricanes Might Not Be Losing Steam As Fast As They Used To (arstechnica.com) 20

An anonymous reader quotes a report from Ars Technica: [A] new study [published in the journal Nature] by Lin Li and Pinaki Chakraborty at the Okinawa Institute of Science and Technology Graduate University focuses on a less-than-obvious question: what happens to hurricanes after landfall in a warming world? Once a storm moves over land, it loses the water vapor from warm ocean waters that fuel it, so it rapidly weakens. The total damage done depends in part on how quickly it weakens. The researchers examined a data set of all North Atlantic landfalling hurricanes between 1967 and 2018. The primary metric they were interested in was the rate the hurricane lost strength over the first 24 hours after landfall. Strength "decays" on an exponential curve, so they boiled this down to a mathematical parameter for decay time.

This parameter varies a fair bit from storm to storm depending on weather conditions and terrain, so the researchers compared averages for each half of the 50-year period. They found a pretty strong trend. In the earlier 25-year period, the average storm lost about 75 percent of its strength over the first day. In the latter half, the average storm lost only half of its strength. The researchers also analyzed sea surface temperatures in this area, which have obviously increased over the last 50 years. That means there's a rough correlation between warmer ocean temperatures and hurricanes retaining strength after landfall. But is there a physical reason to believe the former caused the latter?

To test this, the researchers used a computer-model simulation of an idealized hurricane -- that is, a hurricane in a homogenous virtual setting rather than above a specific location on the Earth. They simulated a series of hurricanes over increasingly warm water, with intensity capped at Category 4, and had each one make landfall at exactly the same strength. Landfall was simulated by suddenly cutting off the supply of water vapor at the bottom of the storm. Sure enough, the storms that had grown over a warmer ocean took longer to weaken. That means this isn't a matter of, say, the back half of a storm still feeding on warm water while the front half crosses onto land. Instead, it appears that increased water vapor entrained within the storm itself helped sustain it. Another set of simulations confirmed this by also removing the water vapor at landfall -- in this case, the storms all weakened identically.

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Hurricanes Might Not Be Losing Steam As Fast As They Used To

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  • The storm count hasn't increased you know! Please ignore inflation-adjusted damage amounts, intensity and all other factors. This is an important talking point my brain has downloaded from conspiracy blogs.

  • ...they've really started to like Team Fortress 2.

  • Did the author think that "losing steam" was a good metaphor to use here, one that wouldn't be atall confusing ?
    Did the editor ?

  • I saw a white crow today. Therefore, crows must be becoming white.

  • It seems the researchers "forgot" to remove all the storms that made landfall and then turned back out to sea...

    Quite the tweet storm forming over that.

  • Anyway, if strength is say wind speed and it depends on the amount of moisture, in the past 60 years, the climate became noticeably wetter because of global warming, which could mean that wetness drops to "threshold" level slower than in the past.

    Seriously, go shopping to NOAA FTP side and check out their precipitation data. You will see noticeable trends towards wetness in many places.

    For example, Sahara moves up, which means that it actually decreases in area.

  • "Global Warming will make storms worse!"
    (a number of QUIETER than normal years stormwise)

    "Well we may have fewer storms, but they're going to be MORE INTENSE - for sure!"
    (storm intensities measured by historical standards don't really change beyond the 'noise' of normal variation)

    "Well, they may not have really gotten more intense, but look at all the $BILLIONS in damage where they used to do $MILLIONS!"
    (studies correcting for property values to current dollars, and then correcting for new additional proper

    • The studies that say hurricanes are getting stronger are based on the dollar amount of damage it does. As coastal cities grow it is obvious that potential damage costs will go up. I am also not sure what the other guy is talking about? I live in Tampa the area that was actually hit by Eta it went from a hurricane to a storm as soon as it made landfall. There was a lot of rain which makes sense as it has been predicted that hurricanes are getting slower giving them the potential to drop more water. However,
  • Since I live in Florida, I have to deal with these. We are still wondering if the Crew-1 launch will happen Saturday night or not, because of the tropical storm currently going through the area. So far it has been pretty much only a lot of rain for my area, except that some stores were packed with people stocking up supplies. It seems rather obvious to me that having more energy available will result in stronger storms.

Were there fewer fools, knaves would starve. - Anonymous

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