Weather Notebook
Bryan Yeaton

Brits and Coriolis
Wed Oct 22, 2003

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"Taking a turn for the worse," in military parlance anyway, could describe a long-range missile that falls far from its target. In the case of an early World War I ocean battle in the South Atlantic, it wasn't poor aim that had British missiles falling 100 yards to the left of targeted German boats; instead, it was a neglected calculation related to the Coriolis force.

Hi, I'm Bryan Yeaton and this is The Weather Notebook.

For the very same reason that air turns in weather systems across the globe, missiles too are forced to veer off to the side. Because of the earth's rotation, they turn to the right in the northern hemisphere, and to the left in the southern hemisphere. In other words, in opposite directions in these hemispheres.. This is the Coriolis force.

During an embarrassing battle in World War I, British battle cruisers engaged two German warships, at a range of nearly ten miles, near the Falkland Islands, but forgot to reverse their Coriolis correction. The British gunners at first couldn't figure out why their artillery was falling astray. They had adjusted the guns. But instead of setting them off to the right to account for the left turn of the Coriolis force in the southern hemisphere, they set them off target to the left, like they did in the northern hemisphere. So, the missiles ended up missing two times more than had they not made any adjustments.. Ultimately, the British eventually won the battle with about sixty direct hits, but not before more than a thousand shells had fallen into the ocean.

Thanks today go to writer Dave Thurlow who lives in Jackson, New Hampshire. The Weather Notebook is a production of the Mount Washington Observatory. It is supported by the National Science Foundation. For more on the Coriolis effect, visit our website at

Thanks today to the entire Weather Notebook staff Doug Sanborn, Melody Nester, Sean Doucette, and Peter Crane.

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