Where Hurricanes Come From

Sitting in Chicago yesterday, observing low clouds rushing south on a gusty northerly breeze — part of the larger circulation of what was left of Hurricane Katrina, hundreds of miles away — my brother John asked something like, “How do hurricanes get started?” I fumbled for a few minutes talking about some of the ingredients that go into a hurricane — warm, warm ocean water, the little atmospheric disturbances that sometimes kick off the big storms, and weak wind shear (vertical winds) that allow the storm’s circulation to get moving. But I realized, gee, beyond those haphazard scraps, I don’t really know.

The question itself is kind of profound, because a quick look through some online references show that while more and more is understood about the process, even supercomputer-wielding climate scientists can’t give a final answer to how the storms start. Obviously, hurricanes get lots of attention from serious science; the lack of complete understanding says a lot about how complex weather processes are.

A few “how hurricanes form” links:

–If you love the Socratic method and aren’t afraid of brushing up against a little high-level science talk, the National Hurricane Center has an insanely long list of frequently asked questions about the storms. To zero in on hurricane origins, go to the basic definitions page and check out “how do tropical cyclones form?

–Lots of more basic explanations are available, including at How Stuff Works. NASA’s kids site has good pages on how hurricanes are created and how they move.

4 Replies to “Where Hurricanes Come From”

  1. I haven’t read any of your links yet, but the question that comes to mind is, what role does man play in contributing to any of these conditions. Particularly, in the warming of the gulf waters. Surely it didn’t get like that by itself.

  2. Well, from the little I’ve read, there’s not much evidence that human activities are making much of a difference, yet, in the ocean temperatures. The Earth heats up, a lot, in the tropics; one of the surprising things about going to Florida in August is to go into the Atlantic or Gulf and discover that, especially compared to the waters I’m used to here in Northern California or from much more temperate Lake Michigan, the sea feels like bath water late in the summer — it’s really warm; one of the little general quasi-scientific scraps I’ve retained about tropical cyclones and their role in climate is that they serve to distribute heat away from the tropics into cooler latitudes in both the northern and southern hemisphere.
    There’s been discussion about whether global warming will eventually touch off cycles of superstorms, and some people point to the hurricanes and typhoons and other big storms of the last decade or two as proof that something like that is already under way. But I’d point out that severe hurricanes were happening long before the Industrial Revolution; at the very least, that means the basic ingredients for violent storms have been around for a long time and that the ocean got plenty warm enough to help the process along with no human help. Of course, that doesn’t answer the question about how much things have changed, or will change, now that humans *are* changing basic environmental conditions. Since scientists are, for instance, still struggling to understand the basic processes that get hurricanes going in the first place, I don’t think anyone can deliver an absolute answer, yet, about the effect of human inputs on big storms. On the other hand, you don’t need to achieve perfect understanding of an issue like climate change before you take it seriously and try to do things that you believe will head off or reduce big problems down the road. Of course, Bush and the “global warming is bad science” community want all the answers before they lift a finger. (Too bad he doesn’t feel the same way about his geopolitical impulses.)
    Having said all that, that National Hurricane Center FAQ provides some science-based answers to those questions: http://www.aoml.noaa.gov/hrd/tcfaq/G3.html

  3. Well, I think one human effect on climate change is pretty clear: humans created the hole in the ozone layer, which allows a much higher intensity of ultraviolet radiation into Earth’s atmosphere, which is raising temperatures on land, in the oceans, and I believe is the reason the polar ice caps are melting, which is raising ocean levels, which means small countries like Tuvalu are disappearing. Are people causing hurricanes? Perhaps not, but we are messing things up faster than natural cycles can fix them – unless this type of natural disaster is actually part of the planet’s reset feature.

  4. I can go along with what I think is the implicit
    assumption of your comment, which is that we need to
    do something to change our ways and limit the impacts
    we’re having on the environment. I agree totally.
    But what I was responding to was the suggestion that
    the ocean water is so warm because of human activity.
    What I tried to say was there’s no evidence of that.
    As far as global warming goes, you don’t need an
    open-and-shut case to take action — the wealth of
    circumstantial evidence on hand is enough.

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