Tropical Storm and Hurricane Frequency

September, 2005: The school year has just begun. The country is still reeling from Hurricane Katrina.

Instead of beginning the year covering plate tectonics (my original plan), I decide to start with hurricanes. As we learn more about Katrina and hurricanes in general, the question keeps coming up in class (and in the media): “Are we getting more hurricanes because of global warming?”

I struggled with how to answer that question. Reports from scientists were mixed. The most reliable sources (IMHO) never made a direct connection between global warming and the trend of more active hurricane seasons. They’d only go as far as something similar to, “hurricanes get their power from warm oceans. In theory, if oceans get warmer, it would make sense we’d see more hurricanes.”

That didn’t cut it for my students. 15-year olds don’t have great appreciation for the subtleties and complexities of meteorological research. They wanted answers.

I stumbled across a website containing records of every reported hurricane and tropical storm from 1851 on. Aha! Oho! Forget the experts, let’s track the trends ourselves!

I split the class into groups. Each group took a decade and recorded the number of hurricanes and tropical storms each year in their decade. Back in the pre-Google Docs era, we were forced to spend 30 minutes or so sharing data and entering into their individual spreadsheets. Today, just create a Google Doc spreadsheet (like this one!) and have each group enter their data (an example of collaborative online documents saving a huge amount of time & boredom).

Then comes the graphing! . I’ve found Google Docs graphs aren’t too great at this now (they might get there soon), but exporting the data to Excel is easy enough.

We added moving average trendlines to see the trends. You can play with how long the moving average should be. We decided that 5-10 years seemed to give a good picture of the trends. The graphs below have trendlines with a moving average of 10 years.

The graphs:

Hurricanes by Year

Tropical Storms + Hurricanes per Year

Fun fact: The first time I saw these graphs was in class (and my students knew that). I didn’t know what trends would emerge. My students and I were learning together, and they seemed to like participating in the discovery of something that wasn’t pre-determined.

Good discussions that fit well with this activity

  • How valid are the counts and intensities for tropical storms before reliable weather satellites and radar were in use? Most storm reports back in the day simply came from ships at sea. How would the data be affected if several storms went unreported each year?
  • Does this information prove causality? (It doesn’t) As much as it looks like it, there’s no way we can say with any certainty that global warming has caused the uptick in tropical storms recently.
  • Would coastal development have occurred at the same rate the last 50 years if hurricanes were as frequent as they have been the last few years? Lots of good discussion can be had as to the wisdom of living on the coast, students seem to have strong opinions one way (you’d be stupid to do this) or another (It’s way worth the risk to live on the ocean).

Whew. I’m feeling a bit like this guy. What can I say? I’m a fan. Comment it up!

Image credit: NOAA via on Flickr

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4 thoughts on “Tropical Storm and Hurricane Frequency

  1. Pingback: dy/dan » Blog Archive » Moar!

  2. I made the mistake of starting with plate tectonics but we have just moved on to cyclones as part of a natural disasters theme. Love your graphs and the original lesson you created ….hope you don’t mind if I borrow them. I won’t have time now to get stuff sorted to repeat your activity, but your questions that can be drawn out of this will be useful. I also admire your ppt on earth structure ……not one of the topics I do with my year 9 students, but I bet this grabbed their attention.
    I hope you keep sharing! Love your work.

  3. @Graham I’m not sure if it’s a mistake to start w/ plate tectonics in general (it all depends on the set-up). I just decided to start w/ hurricanes b/c it seemed terribly relevant at the time. I haven’t started w/ hurricanes since 2005.

    You’re more than welcome to use whatever. If you have any questions, comments, improvements, etc., feel free to contact me. I hope to keep sharing. It was my original plan for the blog. I just haven’t done much with it yet.

  4. Pingback: Earthquake unpredictability | The 25 Hour Day