How Reliable Are Hurricane Forecasts?

Three apparent misses don't tell whole story

For the third time this hurricane season, a storm was forecast to hit New Orleans, only to have the forecast change and the storm to spare us. But does the welcome sigh of relief from "dodging a bullet" only undermine public confidence in future forecasts?

There's always some uncertainty in the forecast, says Louisiana Climatologist Barry Keim.

"The cones are only intended to be correct two-thirds of the time," said Keim. "It just seem like this year, I know we've had a lot of that."

Hurricanes Marco, Laura, and then Sally, were all aimed straight at southeast Louisiana at one point.

Keim says the Laura forecast was actually pretty good, once it got to three days before landfall. Marco fizzled in intensity, but its center did cross the mouth of the river.

"The intensity forecasting, is still very, very poor," Keim said. "There are so many moving parts involved in what goes into a storm blossoming with its intensity or not."

And Keim says slow-movers like Sally always have more uncertainty in their forecasts.

"Slow moving storms, like Sally in particular, the slower they move, it seems, the more difficult they are to predict," Keim, explaining that meteorologists cannot predict steering currents if they are not there, and that is why it took so long for the forecast for Sally to shape up.

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