As height of storm season arrives, forecasters warn not to pay too much attention to 'the skinny line'
It's really the only question: Where's the storm going?
With the start of August comes the height of the hurricane season.
Traditionally, about two-thirds of hurricanes form in August or September. On average, the first forms Aug. 10; Alex, a hurricane, already showed up June 29 of this year and Tropical Storm Bonnie came and went in late July. The first "major" storm, of Category 3 or higher on the Saffir-Simpson scale, on the average, forms Sept. 4.
Now also is the time when storms are more likely to form off in the central and eastern Atlantic Ocean, giving them plenty of time to feast on bathtub-warm water as they move thousands of miles towards the North American coast.
The arrival of the high season also means that now is when people really start looking at those "cones of probability."
And human nature leads most to focus on the "skinny little line."
It doesn't show where the storm definitely will go, but where forecasters think right now it's most likely to go. The storm almost never follows that line exactly, and it can change from one advisory to another.
But people follow it religiously, and if they're not in its bull's eye, they relax.
That can be a mistake.
In 2004, virtually the entire Gulf coast, some 400 miles from Key West to Naples to the Big Bend, was in the cone of Hurricane Charley. But the "skinny line" aimed it at Tampa Bay.
Was the forecast off by more than 60 miles, the distance from there to Port Charlotte?
Not really. Forecasters say it was off by only about a dozen miles - the difference between staying at sea and making the jog that angled it ashore.
"It's not that much of a deviation," National Weather Service meteorologist Robert Molleda told a group of journalists last week . "You all the remember the stories of people in the Punta Gorda/Port Charlotte area saying they were surprised by the storm - despite the fact that they were under hurricane warnings and they were well within the cone."
And in fact, at 5 p.m. on Aug. 12 - less than 24 hours before of landfall - the chances for both Port Charlotte and Tampa Bay getting hurricane winds was 30 percent.
Even the probability cone changes constantly. On Monday, it might show the storm nearing your area by Friday. By Wednesday, it might show the storm nearing a spot on Friday that's hundreds of miles from you.
And forecasters say a third of all storms track outside it at some point.
The cone shows only the most likely places where the absolute center of the storm will strike, not the extent of wind fields, which can stretch hundreds of miles. And they're not consistent. Andrew bent fences in Boca Raton, 80 miles north of its Homestead landfall, but Key Largo, only about 25 miles south, had nearly no wind effects.
In a simulation based on the large, fast-moving 1938 New England "Long Island Express" hurricane, the cone for "Hurricane Shirley" showed it staying off the Carolinas and making landfall around New York.
But it also gave a 90 percent chance of tropical storm force winds along the coast from the Carolinas to New England, well out of the cone.
Such uncertainty makes it tough when forecasters post watches up to 48 hours before landfall and warnings, up to 36 hours in advance.
Storms can do all sorts of things in that time, and even a 30- or 40-mile shift is, meteorologically, a small hiccup.
That means that just because you end up not getting hit by hurricane-force winds, it doesn't mean the forecasters were way off; it just means hurricanes are big and messy and unpredictable. http://www.palmbeachpost.com/weather-new...arn-833908.html