April 12 – Blow Hard

Today’s Factismal: A wind speed of 238 mph was measured on top of Mount Washington, New Hampshire; it was the world’s fastest non-tornadic surface wind gust.

Have you ever wondered why scientists use six words when three might do? It turns out that there is a method to our madness. By adding qualifiers such as “gust” and “surface”, we try to make the exact extent of what we know both more specific and more useful. As an example of why this is necessary, let’s consider the record for the “world’s fastest wind”.

Wind gusts recorded during Hurricane Katrina (Image courtesy NOAA)

Wind gusts recorded during Hurricane Katrina
(Image courtesy NOAA)

Starting at the end, why do we specify “gust”? Because a gust of wind is very different, meteorologically speaking, than a sustained wind (which is also different than a steady wind). Sustained wind is actually the average wind speed over the past two minutes whereas a gust is a brief burst of wind that is much faster than the sustained winds; meteorologists require that a gust be at least 10.4 mph faster than the sustained winds. And a steady wind is just a wind with very few variations in speed or direction. So including the word gust lets us know that the measured wind speed was not typical; as a matter of fact, wind speeds of 35 mph are far more typical of Mount Washington than those of 238 mph. It turns out that the world’s fastest sustained surface wind is from Cyclone Olivia, which blew past an automated weather station on an oil rig off the coast of Australia at 254 mph.

Wind speeds increase up into the troposphere (Image courtesy ESPERE)

Wind speeds increase up into the troposphere
(Image courtesy ESPERE)

OK, but why must we include the word surface? That one is both more difficult and simpler to understand. We call it a surface wind because that’s where this wind was measured. As you go up in the atmosphere, the wind speeds can increase because there is less in the way (trees, houses, mountains); that is part of why the jet stream is found at 35,000 feet and not at ground level – for which everyone is grateful, except kite fliers. If we included non-surface winds, then the record would be held by the jet stream, which has been recorded as moving at a steady pace of 275 mph (though 90 mph is far more common).

The reason that we include “non-tornadic” should be pretty obvious to anyone who has watched “The Wizard of Oz”; tornadoes move air very quickly. How quickly? Well, it turns out that nobody knows for sure. When Fujita developed his famous tornado scale, he actually posited the existence of tornadoes that would spin around at Mach 1! But thus far, the fastest that we’ve ever seen a tornado spin is 318 mph.

Neptune, home to the Solar System's fastest winds (Image courtesy NASA)

Neptune, home to the Solar System’s fastest winds
(Image courtesy NASA)

So about the only word that isn’t needed is “world”, right? Wrongo! If we look at Neptune, it currently holds the Solar System’s record for the fastest wind on any planet – a zippy 1,500 mph!

So it turns out that every word in that admittedly pedantic statement is needed if we want to communicate that the wind was moving abnormally fast for a brief period of time near the Earth’s surface on April 12, 1934: we have to say that the world’s fastest non-tornadic surface wind gust was measured on Mount Washington. Oh, and say that it was moving at 238 mph… 😎

If hearing about this world record has made you hungry to learn more (and maybe take part in a world record of your own), then why not join SkyWarn and help spot severe weather as it forms?
http://skywarn.org/

3 thoughts on “April 12 – Blow Hard

  1. Pingback: April 14 – Nothing but blue skies – Little facts about science

  2. Pingback: December 8 – Smell of success – Little facts about science

  3. Pingback: December 8 – Smell of success | Little facts about science

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