But beware the hype. Here?s what we know now.
How Strong Will It Be?
It?s difficult to imagine Hurricane Sandy?or Frankenstorm, if you prefer?becoming the "worst storm in 100 years" for the northeastern United States, as some forecasters are calling it. To be the storm of the century, Sandy would have to exceed the New England Hurricane of 1938, which made landfall as a Category 3 hurricane with 120- or 125-mph winds. Were the same storm to hit today, it would cause an estimated $47 billion in damage.
Sandy, meanwhile, presently has winds of 75 mph. The science of predicting hurricane intensity is relatively poor (compared with the science of forecasting their path, which continues to improve), but forecasters expect Sandy to weaken under the influence of strong wind shear before strengthening again to 75 mph before a final landfall along the Delaware coast on Tuesday morning.
The storm is especially difficult to forecast because, as it?s coming late in the Atlantic hurricane season, it will be interacting with much colder air moving in from the north. Thus, the storm will ultimately become a combination of a couple of weather systems, including Sandy and a low-pressure system. Hence the name Frankenstorm.
So What Might It Do?
It?s a very large storm. Hurricane-force winds of 75 mph could lash areas of the mid-Atlantic states near where Sandy?s core makes landfall. Now the area of hurricane-force winds is small, but Sandy is expected to have an extremely low central pressure for a late-season storm moving so far north. This very low pressure could make whatever storm emerges from the interaction between Sandy and the low-pressure system over land stronger.
Because of the timing of a full moon in conjunction with the storm surge, flooding is likely in low-lying coastal areas. But where the worst flooding occurs depends on where Sandy comes inland. The worst storm surge will happen within 50 or 100 miles north of its landfall.
If the storm comes ashore in northern New Jersey, as some forecast models predict, there is a chance Sandy?s surge could be pushed into Manhattan, flooding some subways. If the storm comes in farther to the south, in Delaware, this is unlikely to happen.
The two biggest concerns for most northeastern United States residents are inland flooding, with up to 10 inches of rain possible, and power outages. Although Sandy is expected to become an extratropical storm (a step down from a hurricane) by the time it makes landfall, meaning it will lose its warm core, the storm should retain a warm belt of very heavy rainfall. Fortunately, soils are not waterlogged and river levels are not particularly high across the parts of the northeastern U.S. where rains should be heaviest. That was the case with Hurricane Irene last year, which led to 500-year-floods in some areas. And though the area of maximum sustained winds will be relatively small, Sandy is expected to produce a large area of winds gusting to 60 mph or so, which is strong enough to cause tree damage and take down power lines.
Finally?and seemingly improbably, since this is a hurricane we?re talking about?there is the possibility of significant snowfall in the Appalachian Mountains and vicinity. When a warm, moist air mass collides with much colder air, the precipitation that falls turns to snow.
Such "snowicanes" are not unheard of. The Snow Hurricane of October 1804 was a similar late-season hurricane that brought large amounts of snow to New England as an extratropical storm.
If you live in the storm?s path, take action now. Fill your prescriptions. Get a full tank of gas. Visit the grocery store, and don?t forget to stop by the ATM, in case your region loses power and credit card machines are unavailable.
Eric Berger writes the SciGuy blog at the Houston Chronicle.
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