https://x.com/nbergwx/status/1843444771135861007?s=46&t=9FPxCfjU5uuRXH3QXtrs8w
From this tweet. Additional, how would we know, and how would this be a stationary target given global warming or general changes?
In: Planetary Science
Kerry Emanuel at MIT has defined an estimate for the “maximum potential intensity” for a hurricane by balancing dissipation due to drag vs. the energy released by treating the hurricane as a heat engine. Basically this depends on the temperature of the surface vs. the temperature of outflowing air at the bottom of the stratosphere. The bigger this difference is, the stronger the storm you can have.
Hurricanes need to get their energy from somewhere. And that comes from warm water, all else being equal the warmer the water the stronger the Hurricanes can get.
He is basically say that, based on our understanding of physics/weather, this hurricane is about as strong as it can get based on the current conditions. I have no idea if that’s actually true, but that’s the idea. edit: About being at the current limit, I mean. The thing about warmer water allowing stronger hurricanes is definitely true.
So, the tweet in question is likely referring to the conceptual model of hurricanes as being [a Carnot heat engine.](https://en.wikipedia.org/wiki/Carnot_heat_engine) Basically, this is a system that converts thermal energy into kinetic energy. In a hurricane, this translates to the conversion of heat from warm, moist tropical oceanic air into kinetic energy (wind). So, you start out by having a weak low pressure center. Air spirals inward from high pressure to low pressure. As air spirals inward towards a central point, it converges and mechanically forces upward motion. Warm, moist air is less dense than cool, dry air, so the warmer & moister the converging air, the more likely it vigorously rises. As air rises, it leaves behind a “hole” that needs to be filled, causing more air to rush in to fill that gap and spiral inward. A lower pressure at the center, caused by this vigorous upward displacement of air, results in a stronger gradient of pressure between the center and the surrounding environment which in turn drives more vigorous winds.
Tying it all together, we can see that the temperature and moisture content of air is related to its ability to be displaced upward. The warmer and moister the air, the more likely it is to rise without facing any strong opposition. As upward motion is enhanced, it leaves behind a bigger “hole” that needs to be filled (low pressure center). The bigger the hole, the faster air will rush in to fill it (winds). Some of the energy associated with winds are dissipated by surface friction. So long as there isn’t anything to mess with this process, the hurricane will continue to intensify until it reaches a point where the conversion of thermal energy into kinetic energy is balanced by the dissipation of kinetic energy by surface friction. This point would be the theoretical maximum strength of a hurricane. Warmer sea surface temperatures allow for warmer, moister near-surface air. So the warmer the ocean, the higher the theoretical maximum strength of a hurricane.
However, I have to stress that this assumes nothing exists to mess with the process. Within the context of climate change, there are external factors (such as an increase in wind shear – how the speed and direction of winds change with height) that could act opposite increasing ocean temperatures. This means that even though ocean temperatures are warmer, which would theoretically act to support stronger hurricanes, if wind shear were to increase as well it would inhibit this potential for hurricanes to become stronger. We don’t understand very well how hurricane frequency will change in a warmer climate because of this. We do have moderate confidence that they will likely become more intense.
A more involved explanation of this process (and an equation that estimates the theoretical upper bounds of a hurricane’s strength) can be found in this [great writeup](https://pubs.aip.org/physicstoday/online/12200/How-strong-can-a-hurricane-get) by Falko Judt at the National Center for Atmospheric Research.
EDIT: u/onewhitelight provided an actual ELI5 explanation that is worth repeating here: The low pressure center of a hurricane is like a valley. The lower the pressure, the “steeper” the valley. A steeper valley means objects can more quickly roll down the slope towards the bottom (think of this as the wind). When the ocean is warmer, it acts to support a “steeper” valley. However, the rate at which you descend into the valley eventually evens out. You can keep going faster and faster but eventually your acceleration will be balanced by restoring forces (friction) and you’ll reach a constant velocity.
Weather on Earth is basically the system balancing itself out and the system can only change so fast given the available energy.
Think of it like a tub. The tub filling is the ocean water building up more and more energy through heat. The hurricane is the drain in the tub taking that energy back out. When the tub is barely full to a little full, how fast it drains goes up in speed (small storms, tropical depression, cat 1-5 storms), but once the tub reaches a certain fullness, it won’t drain any faster (cat 5+ storms). If the water were even hotter, it could get even bigger (drain faster), as that’s more going into the tub again, but for the given heat right now, it is draining full speed.
[removed]
[removed]
Air has friction. As hurricane winds get faster, there is more friction resisting them.
Hurricanes get power from warm ocean water. Depending on the ocean temperature, there is only so much power available to overcome friction and make stronger winds. This is why big hurricanes usually happen in the late summer and early fall, when the ocean is warmest.
Physicists can calculate the maximum wind speed that a hurricane can achieve for a given ocean temperature. *This is not stationary.* As the ocean warms due to climate change, this maximum wind speed increases.
When he says the hurricane is “nearing the mathematical limit of what Earth’s atmosphere can produce,” he’s saying that this storm is almost as strong as a hurricane can possibly get on our planet.
Hurricanes need specific conditions—like super warm ocean water, low pressure, and just the right wind patterns—to get stronger. But there’s a point where, no matter how perfect those conditions are, the storm can’t get any more powerful because the atmosphere just can’t hold that much energy.
Think of it like filling a cup with water: once the cup is full, it’ll just overflow if you add more. Similarly, the atmosphere has a “full” limit for how much power it can support in a hurricane. If a storm tries to get stronger, it would need conditions that just don’t exist on Earth (like even hotter water or much lower pressure).
So, this storm is pretty much at that max point, like a balloon that’s stretched as far as it can go without popping. It’s as strong as it can get based on what our atmosphere allows—almost like reaching a “game over” point for hurricanes.
ELI5 explanation:
Get a rubber band, pull it back. It’s stored energy. There’s a maximum energy you can store in that rubber band. When you release the band and it snaps you get that back in movement. You can’t get more energy that’s stored.
You can calculate what the (mathematical) limit is.
Warm air/water holds energy. That’s like getting a stronger rubber band. You can also calculate how much energy is stored. So there to you can get the maximum energy that can be generated from that stored energy.
Warmer air holds more moisture/energy. Warmer water holds more energy. So the warmer the planet gets, the more potential energy that can be delivered to a storm and the devastating the storms can become.
Man made climate warming is a hoax. They found Stonehenge type stones 40 feet under the water of Lake Michigan. A stone has a mastodon carved into it. That lake water rose 40+ feet in 9000 years. That is how long the ice has been melting and raising sea levels. Long before man started creating greenhouse gasses.
Latest Answers