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19 September 2003

Hurricanes and Seasons

Mid-September is the peak of hurricane season, and Hurricane Isabel has been pounding the east coast. Next Tuesday, September 23 at 3:47 A.M. PDT, happens to be the autumnal equinox, the official end of summer. Tropical storms need heat and water vapor to develop. So why is the peak of hurricane season so near the end of summer? After all, the days have been getting a bit shorter ever since the summer solstice on June 21! As an oology bonus stumper, is there any good reason why it would be easier to balance an egg on its end on the equinox?

NASA photo (also here) of Hurricane Isabel approaching the east coast on September 15, 2003. This started as one of the strongest storms of the century, but it fortunately weakened as it approached landfall. Why do these huge tropical storms that depend on heat often develop months after the longest day of the year on the summer solstice?

The peak of hurricane season falls near the end of summer because this is when the ocean is warmest. That's another stumper because the days have been getting shorter ever since the summer solstice on June 21. It's the same reason that the first batch of pancakes takes longer to cook than the second -- you have to heat the griddle. The land, the air, and especially the oceans are slow to warm, but they hold their summer heat long into fall and skew the seasons. For the oology bonus stumper, I'm sure if more people try to balance eggs on the equinox, then more will succeed. That's it.


Put a teapot on the kitchen stove. Of course it takes time to warm up because of the thermal inertia of the water. Tropical storms are powered by warm ocean water. That's why the peak of the Atlantic hurricane season (at least) comes well after the longest day of the year and extends into fall rather than spring. Our seasons are skewed past the equinox and solstice days because the air, the land, and especially the oceans take extra time to gain and lose the heat. Another extraterrestrial example is that the dust storm season on Mars begins with perihelion when Mars is closest to the sun.

It's a recent urban legend that it's easier to balance eggs on the equinox than any other time. We're studying eggs in my science classes at Dunn Middle School, so this was a convenient exercise to introduce scientific method at the beginning of the school year before the kids do their own eggsperiments.

On September 17, 2003 - a week before the equinox - 29 of 60 kids managed to balance an egg on end in a ten minute period. On the September 23, 2003 equinox, 28 of 59 kids managed to balance their eggs during the same period. That's 48.3% before vs. 47.5% on the equinox. The lesson is that you can balance an egg any time if you work at it. It's no mystery. Look close at any egg and you'll will see that the shells have tiny bumps and ridges that can support the egg when it is settled just right. A bumpy table helps.

There are other ways to balance eggs. Sprinkle some salt on the table first and then wiggle the egg until it settles on the cubical crystals. Then blow away the extra salt and no one will notice. Another story is that Columbus won a bet by setting down his egg hard enough to crack the shell without rupturing the membrane. Moral: successful people don't always follow the rules, but don't push too hard!

"Oology" really is the word for the study of eggs, pronounced "OH-ology". It's a fun word because it looks like what it means. How about "Mology" for the study of mountains and "Sology" for the study of snakes? Can you think of others?

Here are some links for your own research:

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