BOSTON (CBS) – The cone of uncertainty.

The name doesn’t inspire a great deal of confidence, but it is a valuable tool in hurricane prediction.

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“The cone of uncertainty describes where we think the center of the storm, the hurricane is likely to be and it’s designed so that, roughly two thirds of the time, the entire track of the center of the storm falls within the cone,” James Franklin, Chief of Forecast Operations at the National Hurricane Center, told WBZ-TV.



Even if you are outside of the cone, that doesn’t mean you aren’t at risk. One-third of the time the storm can move outside of the cone. However, it doesn’t tell you much about the risk. As forecasts become more and more accurate with time, this cone continues to shrink.

“The cone will be a little bit smaller this year, about 5-percent smaller. Our track forecasts get a little bit better every year and as a result that cone tends to shrink just a little bit,” says Franklin.

If you find yourself sitting within the cone, what are the actual chances of a direct hit?

It all depends on how much time there is between you and the storm.


For example, if the storm center is 5 days out, the center of that hurricane could fall within a 270-mile stretch, which is approximately the distance from Boston to Philadelphia.



When the storm is 4 days away, you have a distance of error of about 200 miles, roughly the distance from Boston to New York City.

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When the storm is 3 days away, the distance narrows to 132 miles, which is similar to a trip from Boston to Albany.

If the storm is 2 days away, the storm could fall within a 97 mile-stretch two-thirds of the time, in other words, the distance between Boston and Hartford.

When it’s 36 hours away, the distance drops to 75 miles, so it would like Boston to Springfield.

A day away and the distance decreases to 56 miles, from Boston to Providence for reference.



Only 12 hours out and the storm can land within a 35-mile stretch two-thirds of the time. That’s basically the drive from Boston to Worcester.

Now that we are able to forecast the path of a hurricane so much more accurately compared to the early 2000’s (when the cone was first used), there are several other new products being developed by the National Weather Service to help you understand the potential impacts to your community.



“Hopefully with those new products that we can convey the message a little bit more clearly and define the area of greatest risk. When you go out just generally with a hurricane warning, and, let’s say you blanket a populous, well, everyone is in the warning. That doesn’t mean that everybody across the populous is going to receive the same amount of impact,” says Benjamin Sipprell, Meteorologist at the National Weather Service in Taunton.

Now, just as they have done with winter storms, the National Weather Service will be providing detailed impact probability maps during hurricane season. Thus, helping to highlight those at greatest risk from the number one killer in hurricanes – the storm surge.

Flooding from Hurricane Bob. (1991 WBZ-TV file image)

Flooding from Hurricane Bob. (1991 WBZ-TV file image)

“It’s not the wind, it’s generally the water,” says Franklin.

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“Be aware, be prepared, and then take action,” says Sipprell.