How To Read A Hurricane Forecast

Sep 6, 2019

Credit Petrovich12 / Adobe Stock

Floridians are no strangers to hurricanes. But for nearly a decade the state saw no direct landfall from a tropical cyclone. Now after consecutive years of major hurricanes, some citizens seem to have a kneejerk reaction when a storm system nears. That, added to the intensity of recent storms, has some questioning the accuracy of storm path projections. Meanwhile, meteorologists say their technology is working better than ever.

On August 28th, in the central Atlantic Ocean, tropical storm Dorian became a Hurricane. At that time, where it would go and how powerful it could become was uncertain. Two days later, on August 30th, Governor Ron DeSantis gave a hurricane briefing from the State Emergency Operations Center in Tallahassee.

"I think there’s a pretty high degree of certainty that this is going to be a major hurricane. Category 4 potentially even Category 4 plus," announced DeSantis.

While he was certain the storm would become more intense, he wasn’t sure where it would go. One of the projected paths showed it could impact the Panhandle where residents are still recovering from Category 5 Hurricane Michael.

Governor DeSantis speaks to the press at the State Emergency Operations Center.
Credit WFSU

“It’s still too soon to tell whether that’s happening and as I say, not every path of the storm has the same probability but you’ve got to be prepared for that," said DeSantis.

Later that day Gulf County School Superintendent Jim Norton decided to cancel school.

“Honestly why we made the decision we did, we’re certainly not out of harm’s way yet. I hope that I made the right call for the wrong outcome. I hope it’s a beautiful day and people wonder why we canceled school Tuesday," said Norton.

Norton’s district was hit hard last year by Hurricane Michael. He says mostly everyone is still recovering.

“We’re all worn out. I’m in a lot of those who lost their home and still haven’t gotten into a permanent situation since last October. We have a lot of blue tarps on roofs all throughout our neck of the woods,” said Norton.

Norton believes canceling school allowed students and their parents to have ease of mind going into Labor Day weekend.

"Here 10 months, almost a year later, I’m not sure we’re not fighting our toughest battles right now as we try to rebuild our lives in this little 40-mile stretch about 90 miles inland, that truly was ravaged by the effects of Hurricane Michael," said Norton.

And his call to cancel school turned out as he hoped. Dorian went wide right. 

Longtime Meteorologist Nancy Dignon thinks canceling school isn’t too big of an issue, but does worry about the decision being made when the storm is so far out.

"I’m a little more concerned when it’s somebody that’s not necessarily in the direct area where... you know it’s going to be the boy that cried wolf. We’re going to do it too many times and then maybe we’re really heightening the nervousness when the real storm actually comes are way," said Dignon.

Dignon says calling out four days is probably too soon because the level of uncertainty in forecasts is still very high.

"The average track error for a four-day forecast is 175 miles either side. The average track error for a five days is 225 miles. So in the short term the cone is narrow cause there’s more confidence and more accuracy, but it gets really big," explained Dignon.

Dignon says people put too much faith in those early projections.

"So we got to Saturday people were going to the football game and they saw a little bit of a right adjustment and they said “oh it’s not coming don’t worry about it,” they went to the game and then they dismissed it. “We’re done!” And then it started to nudge a little bit back. The thing is people have to remember what a cone means."

The cone of uncertainty is developed by the National Hurricane Center. It represents the probable track of the eye. But as Dignon explains the cone is made from a group of circles drawn to show where the storm might be at a specific time. The larger the circle, the farther out and more uncertain the location.

"In this circle is let’s say 75% of the time wherein 24 hours the center of the storm is going to be contained within. And then here, it’s a little bigger circle to its north. But in two days a longer time, it’s a bigger area because there’s less certainty, we believe that in 2 days the center is going to be in there. And then in 72, you can see what’s happening," said Dignon.

Once all the circles are drawn a line connects them creating the cone. And while that uncertainty may be frustrating, Ryan Truchelut, Chief Meteorologist at Weather Tiger, says the tracking system is much more accurate than in the past.

"Forecast track errors have declined significantly in that past three decades. In fact, currently a 5-day forecast point from the National Hurricane Center is as good as a 2-day forecast point was 30 years ago."

Truchelut also says predicting the intensity of storms has become easier. When asked about the recent increase in the number of major hurricanes he says it’s too soon to say climate change is impacting it, but Dignon says stronger storms are more likely.

"I don’t want to say we’re only going to ever see those, but we are seeing a trend towards some of the stronger hurricanes," said Dignon.

Both Dignon and Truchelut believe the best way for people to know where a Hurricane is going is by listening to local emergency management officials.