Thursday, August 16, 2007
360 Asks: Chad Myers on hurricanes and earthquakes
Editor's note: With both earthquakes and hurricanes in the news, we decided to ask a few questions of CNN Severe Weather Expert (and 360 contributor) Chad Myers.

Q: What causes a hurricane to change speed or to change course?

Chad Myers: Hurricanes do not determine their own path, rather they depend on upper-level steering winds to determine their course. These upper-level winds come from other large-scale weather patterns in the area, such as large areas of high pressure, cold-fronts, or troughs. If none of these are present, hurricanes will stay relatively motionless. If the hurricane moves into an area of strong steering winds, it will speed up. Forecasting the future path a hurricane consists of forecasting exactly how many different weather features will evolve, which is a very difficult process. That is why a projected path is often subject to large errors five or so days in the future. In fact, the computers that run "models" are some of the fastest in the world and still they are still not close to perfect.

Q: Why does hurricane season occur during the summer/fall?

Myers: Hurricane season for the North Atlantic officially begins on June 1st and ends on November 30th. That is not to say, however, that storms cannot form before or after the official season. One of the ingredients necessary to form tropical systems is an ocean temperature of at least 80 degrees F. The warm water evaporates, forming water vapor, which is the "fuel" for the storm. Ocean temperatures for most of the North Atlantic only reach this temperature during the summer and fall, making conditions right during this time for the formation of tropical storms and hurricanes. In other parts of the world, such as the western Pacific, the water can be warm enough all year to support storms.

Q: Much has been reported about the controversies at the National Hurricane center. Can we feel confident those problems will not affect the center's ability to predict hurricanes?

Myers: We have full confidence in the National Hurricane Center's ability to fulfill their duties despite the recent controversies. The NHC staff contains many of the leading experts in the world regarding tropical cyclone formation and prediction, and they keep each other accountable for their forecasts. Just like any office, there are problems from time to time, but they are professionals and I think we can count on them to keep us informed of any dangers to our coastlines.

Q:Now, regarding the earthquake in Peru: Where was the epicenter?

Myers: The earthquake was centered just off the western coast of Peru, 25 miles west-northwest of Chincha Alta and 90 miles south-southeast of Lima, according to the U.S. Geological Survey. The hypocenter, or focus point of the earthquake, was 19 miles below the Earth's surface. The epicenter is the point on the Earth's surface directly above the focus point.

Q: Why is the depth of the quake important?

Myers: Generally, the effect of the earthquake is less the farther you get away from the center. Therefore, earthquakes that are very deep, several hundred kilometers below the Earth's surface, are felt less on the Earth's surface. All the layers of rock and solid earth between deep earthquakes and the surface can act as a buffer zone and "cushion the blow" so to speak. Shallow earthquakes (within 70 km of the surface) normally result in much more violent shaking of the ground.

Q: And if it was at sea, why was there not a significant tsunami? And what is the relationship of earthquakes to tsunamis?

Myers: There was a tsunami triggered from the earthquake according to the Pacific Tsunami Warning Center, but it was very small and caused no damage. Tsunamis can be triggered by many things, including landslides and mass earth movements underwater, most of which are caused by earthquakes. A tsunami is caused by rapid displacement of the water caused by the earthquake, which results in a wave crest and trough. The size of the tsunami depends on the amount of water displaced by the earthquake, which depends on precise details of the individual earthquake, such as depth, location, and type of earthquake triggering mechanism. A large earthquake that occurs underwater does not necessarily mean a destructive tsunami will result.
Posted By CNN: 7:13 PM ET
  6 Comments
Thanks, Chad, for the info. I can't say I'm an expert on hurricanes and earthquakes after reading the information you shared, but I feel more knowledgeable on it now. We should also note that global warming has an adverse effect on hurricanes, making them more extreme as we've seen of late.

Thanks,
Lilibeth
Edmonds, Washington
Posted By Lilibeth, Edmonds, WA : 7:59 PM ET
Please ask Chad Myers about the "la nina" weather pattern that has supposedly been the reason for this year's freaky weather .

Maybe instead of the global warming fall back, we'll see the scientific reason for all this extreme weather.
Posted By R. Savdoval , San Francisco, Ca. : 8:27 PM ET
Hi Chad, Thanks for the very informative info. Living in California all my life, I've rode out alot of earthquakes. Yet every single time one hits, it's always a shock.
It's unexpected, even when you know it's possible any day or night. The ground under your feet no longer feels solid and the noise is just something you can't explain. My thoughts go out to the people of Peru. Take Care
Posted By Lorie Ann, Buellton, Calif. : 8:47 PM ET
AC360

I have followed this almoct constantly from the beginning, as I do every time.

I've been so wrong so many times I promised I wouldn't get in so deep this time, yet here I am again.

I had finally accepted the idea that these men were lost to us, but Mr. Murray didn't give up, now there seems to be a tiny little hint that maybe they are still alivr.

I never appreciated what my Aunt went through when my Uncle was a miner for I was just a child. I only remember the wail of the siren from the hill. Just considered excitement for small children.

Maggie
Posted By Maggie, Grain Valley, MO : 8:56 PM ET
Thanks to Chad Myers for the info. Really interesting and informative as usual.

I guess there's a whole lotta shakin' goin' on in the world nowadays !
Posted By Kelli - SanFrancisco, Ca. : 10:00 PM ET
I was in the Mexico City Earthquakes in 1985 when I was a kid(8.1 almost 3 min. long, and 7.5 aftershock) and I know it can take years to get your life back. One of the hardest things for survivors other than guilt is that people forget when the next big story comes up. It's easy to feel like the world abandoned you, so thank you for covering this, and please continue to. My heart goes out to all.
Posted By Michelle C., San Diego, CA : 6:09 AM ET
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