Understanding hurricane Sandy: A cocktail with a mighty punch

AFP , Tuesday 30 Oct 2012

Such a friendly sounding name on the surface, such a rare and devastating cocktail roiling within

Understanding Sandy: A cocktail with a mighty punch
Hurricane Sandy is seen on the east coast of the United States in this NASA handout satellite image taken at 0715 GMT, October 29, 2012. (Photo: Reuters)

You name it and Hurricane Sandy and the posse of titanic weather events accompanying it have them: humongous size, unusual staying power and plenty of high-tide sea water to wreak havoc, perhaps repeatedly, as the full moon and thus high tide roll in with exquisitely bad timing.

Sandy already killed 66 people as it churned up from the Caribbean, ripping down houses and trees and wreaking other kinds of havoc in the Jamaica, Cuba and Haiti.

But now, as it spins menacingly toward the US East Coast, with landfall expected sometime Monday afternoon or Tuesday, it is morphing ominously into something else -- from a tropical storm fueled by warm sea water to a different kind of storm that runs on contrasts in temperature.

Of that there is plenty. The core of Sandy is still tropical. But it is wrapped by cold air from a 'nor'easter coming from the north, by cold air coming from the jet stream to the west and by coldish air coming from the south.

So Sandy is getting hit from all sides -- streams of gasoline fueling a fire.

And while most hurricanes tend to drift back east after making landfall, these powerful buffers will make it actually head west, inland, with forecasters saying it will even dump snow.

"These energetics are allowing it to maintain its strength," said Todd Kimberlain, a forecaster at the National Hurricane Center in Miami.

Radar images showing the cowering US East Coast and the white, swirly mass of Sandy are indeed jaw-dropping.

Allusions have been made to the so-called "Perfect Storm" of 1991, which inspired a book and a movie of the same name. Meteorologists say some of the same factors are converging this time but in a more fierce fashion, and with greater impact onshore and inland.

Hurricane-force winds stretch out 175 miles (289 kilometers) from its core, and weaker, tropical-storm force winds go out a stunning distance of nearly 500 miles (780 km).

That's due in part to the extremely low pressure at the core. The wind in a storm like this is caused by the pressure gradient -- the difference in pressure at the eye and the edge.

If somehow you could stand at the nucleus of Sandy, you would not gasp for breath or otherwise notice the difference, Kimberlain said. The pressure in mile-high Denver, Colorado, for instance -- where the air is so thin it takes a few extra minutes of boiling to cook rice -- the pressure is even lower.

But because Sandy has such staying power, Kimberlain said, "once it hits the coast it will be at one of the lowest pressures on record."

Then, there's all that water. The moon will ease into its full phase Monday afternoon, and with it comes full tide on the eastern seaboard.

"Heaven and Earth may be aligning to turn Sandy into a real monster, just in time for Halloween," the climate-monitoring website Accuweather.com said Monday.

Sandy's storm surge, forecast to cause coastal flooding of up to six feet in some states, like North Carolina, will be bad enough.

"But superimpose on top that the effect of the full tide and you get a couple extra feet," Kimberlain said.

This is one of the most dangerous aspects of this storm, he said. Making matters worse, as Sandy is going to stick around for a few days, this coastal flooding could go through several tidal cycles.

Some forecasters are tripping over each other with doomsday predictions.

"History is being written as an extreme weather event continues to unfold, one which will occupy a place in the annals of weather history as one of the most extraordinary to have affected the United States," senior meteorologist Stu Ostro of The Weather Channel wrote Monday.

He added: "This is an extraordinary situation, and I am not prone to hyperbole."

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