Friday 15 September 2017

What causes storms and hurricanes?

And this is the one that a lot of people don't understand, and which is most often ascribed to a supernatural entity smiting the wicked, where "wicked" is defined by the various speakers as "people I disapprove of".
But again, it's a natural phenomenon. Here's how it works.

You have an ocean, and you have the sun. And this mostly happens near the equator, where you get lots of sun. The sun warms the water. And the sun evaporates the water. So you get warm, moist air near the surface of the ocean. But hot air (and warm air) rises, because it's lighter than cold air.Up it goes!

And the rising warm, moist air is replaced by cooler air coming in from the sides. But that gets heated up and moistened, so it also rises, and in comes more cooler air.

As the cooler air comes in, it's pushed by the Coriolis Effect. That makes the incoming air swirl, in the classic pattern you see with hurricanes as seen from above.So they swirl clockwise in the Southern hemisphere, and anticlockwise in the Northern.

So you get this huge, swirling cloud, and the winds can be pretty strong; a "category 5" hurricane has winds blowing at 156 mph. Irma, which hit Florida recently, was category 5.

A typhoon is just another word for a hurricane. A tropical storm is also the same thing, but less fierce.

So the hurricane swirls and the swirl drifts relative to the earth's surface. It's very difficult to predict which way it's going to go, it's so very very complex. People make guesses (actually, it's a bit more than a guess) but you shouldn't treat those forecasts as totally accurate.

The only way to deal with a hurricane is to get as far away from it as you can, and don't leave it till the last minute, because that's what everyone else is doing, and you'll get caught in an almighty traffic jam. A second thing you can do, is build your buildings with hurricanes in mind, if you live in a place that gets hurricanes. The third thing you can do, is what I do. I live in a place that doesn't get hurricanes, except that we did get the Great Storm of 1987 with wind speeds up to 100 mph, knocking down 15 million trees! And it knocked down a brick wall in my garden; we heard a great "THUMP" but stayed indoors; later when it was all over, we saw the broken wall.

When a hurricane drifts over land, it's cut off from the source of its food, the warm ocean. So as it goes over land, it loses intensity, which is nice. But if it then goes over water again, it can pick up strength. Irma did that. It birthed just of the coast of Africa, travelled across the Atlantic gaining strength as it went, hit the Caribbean, hit the Bahamas (and weakened to a Category 4), but then strengthened back to Cat 5. Cuba weakened it again, but it was still intense when it hit Florida.

Irma killed 82 people, and did more than $60 billion in damage. Awesome.

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