Forecast tracks: What you need to remember

BY MAX CHESNES AND MICHAELA MULLIGAN Times Staff Writers

It happens every year: A new hurricane season begins, and the forecast graphics start trickling in. Online, your friends and family share maps with multicolored blobs. On TV, the strands of spaghetti models twist and turn through the tropics. Forecast information is everywhere. You think you know what it all means but do you really?

Accurately interpreting hurricane forecasts is a crucial skill in evaluating the risks you face from a looming storm. As with Hurricane Ian in September, information can change quickly and reshape your risk level. Your home could be placed under a hurricane watch, or a storm surge warning, from one hour to the next.

With hurricane season upon us, let’s review how to interpret forecast graphics.

Tropical weather outlooks have been extended

When the hurricane season kicks into high gear, the National Hurricane Center’s tropical outlooks can look something like a chaotic game of tic-tac-toe. On a map of the Atlantic Ocean to the Gulf of Mexico, colored X’s and O’s often dot the graphic. These symbols represent areas of disturbed weather the hurricanecenter is watching.

These outlooks, which the hurricane center releases four times a day (at 2 a.m., 8 a.m., 2 p.m. and 8 p.m. during daylight saving time), show the genesis of storms. They are helpful in understanding when and where a storm could form.

Forecasters do not use them for tracking storms. Instead, these outlooks show the likelihood a disturbance will become a tropical cyclone which can be as lowgrade as a tropical depression with maximum sustained winds of no more than 38 mph.

In years past, these outlooks gave the likelihood of a system becoming a tropical cyclone within two days and five days. But this year, the outlooks will be for two days and seven days out, said John Cangialosi, a senior hurricane specialist at the hurricane center.

The hurricane center began experimenting in-house with a seven-day outlook in 2018. Now, forecasters are confident in their ability to deliver these probabilities to the public.

“We’ve done this for a while and also felt that our skill was very good,” Cangialosi said. “So that’s the reason we’re going forward with it this year.”

The hope is that it will provide forecasters, emergency managers and citizens extra time to prepare ahead of storms.

This year, the outlooks will look the same, except the five-day outlook will be replaced with the seven-day outlook.

When a disturbance pops up in the forecast area, a colored X will mark the location of the system.

The color of the X corresponds to the chance the disturbance will turn into a tropical cyclone. A yellow X means there is less than a 40% chance, an orange X is a 40% to 60% chance and a red X is greater than a 60% chance.

The two-day outlooks number the disturbances and give the probability of formation in 48 hours on the map.

If a disturbance becomes a tropical depression (with sustained winds that are no more than 38 mph), it will turn into a red circle.

A tropical storm, which has maximum sustained winds of 39 to 73 mph, forms after a tropical depression. Once a storm reaches maximum sustained winds of at least 74 mph, it becomes a hurricane. Each tropical cyclone’s location can be found on the map.

To learn more information about the disturbances, you can hover over or click on its corresponding symbol.

The longer outlook will

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Forecasts

continued from 21HH probably be most useful for areas farther east, like portions of the Caribbean, Cangialosi said Tropical systems have an affinity for forming in the Caribbean Sea, where waters are balmy.

Understanding the “cone of uncertainty”

You’ve got the X’s and O’s out of the way. Now let’s talk about the cone.

Once a storm officially reaches tropical depression strength that’s maximum sustained winds of no more than 38 mph forecasters start including the infamous “cone of uncertainty” on their graphics.

Every hurricane season, there’s a push from meteorologists to drive home what the cone means, and what it doesn’t mean. There’s good reason for that: Many people get it wrong.

In a study published in October 2022, a team of University of Miami researchers surveyed Florida residents about whether they know how to accurately interpret the cone graphic. Of those surveyed, 44% incorrectly thought they could determine the forecast size of the storm, and 40% answered incorrectly that they could identify areas where damage will occur.

Here’s what the cone does tell you, based on historical data: There is a two-thirds chance the storm will stay inside the cone. But there also is a one-third chance it will not. In other words, based on past forecasts, the entire track of the storm is within the cone roughly 60 to 70% of the time.

“It’s a visual depiction of where we think the center of the storm is going to go,” Cangialosi said.

What the cone doesn’t tell you, according to the National Weather Service: The size of the storm, and the impacts both within the cone and outside the cone.

“The cone doesn’t tell you where those impacts are going to be because sometimes storms are really lopsided and they get so much weather on the right side,” Cangialosi said. “You could be way outside the cone and still get a lot of conditions.”

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