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Interpretation der Hurrikanvorhersage des NHC

Verfasst: Mittwoch 5. Oktober 2016, 19:35
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Many people assume that the boundaries of the cone show the limits of where this particular storm could go.

That's false.

In addition, one might think that as long as people live away from the centerline in the graphic, which is the predicted storm track pertaining to where the storm's center will go, then they won't experience significant affects of the storm. That, too, is false.

lso, one might perceive that if they are located close to the edge of the cone, they are at less risk of seeing hurricane impacts than if they are located closer to the center. That, too, is not necessarily the case.

Here's what the cone of uncertainty graphic actually means. Now stay with me for a second, because it's kind of technical, but I'll unpack it for you, I promise.

First, there's the centerline. The orange circle indicates the current position of the center of the storm, in this case, Hurricane Matthew. The black line and dots along it show the forecast track from the National Hurricane Center at the time intervals indicated. The letter inside the dot shows the forecast intensity at that time. The letter "m" indicates a major hurricane of Category 3 or greater, whereas an "H" indicates a weaker hurricane of Category 1 or 2 intensity.

The forecast cone indicates forecast uncertainty, but here's the tricky part: It does not show the uncertainty for Hurricane Matthew in particular. Instead, the solid white and stippled white areas show track forecast uncertainties for days 1 through 5 of the forecast, based only on historical data.

Here's how the NHC describes the uncertainty aspect of the cone:

"Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time."

In other words, about one-third of the time, the center of the storm, and the most intense winds and storm surge impacts associated with it, will veer outside of the cone.

In fact, many computer model projections of Hurricane Matthew currently veer to the left or right of the NHC's consensus-based line within the cone.

The NHC further describes the cone's uncertainty estimates: "To form the cone, a set of imaginary circles [is] placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years' official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles."

Peer-reviewed scientific studies have shown that many people fixate on the centerline and assume that if they are located away from it, they are not going to be severely affected by the storm. A 2007 study, published in the Bulletin of the American Meteorological Society, for example, found widespread confusion about the "cone of uncertainty."