Another hurricane season has arrived. Here’s how meteorologists make those long-range predictions.

This is the first part of a new reporting partnership between The Virginian-Pilot/Daily Press and WTKR News 3.

As the East Coast gears up for another Atlantic hurricane season, this one coming 20 years after Isabel devastated parts of Hampton Roads, meteorologists locally and nationally are looking for signals of how 2023 may go.

Here’s how they do it:

Several entities such as the National Oceanic and Atmospheric Administration, AccuWeather and The Weather Channel have released their own predictions. Each varies slightly — from how many tropical storms may end up on the East Coast to how many end up named or considered “major.” Despite the differences, most meteorologists who develop these use the same aspects of weather and climate to make a scientific guess as to how many tropical storms or hurricanes will end up in the U.S.

One of the biggest pieces of the prediction puzzle is sea surface water temperature — which fuels storms. Specifically, water that is about 80 degrees or warmer causes the air to rise, and the rising air creates thunderstorms. Those thunderstorms become complex and eventually turn into a tropical system. As cities along the coast of the southern United States have seen warmer temperatures overall, this affects what time of year ocean temperatures reach 80 degrees or warmer. Warmer water also affects the severity of a storm.

For long-term forecasts, meteorologists also look globally to predict potential impacts on storms. Those projections include the effects of a La Nina or El Nino system — climate patterns in the Pacific Ocean.

El Nino is expected to develop over the next couple months. During El Nino, westward-blowing trade winds weaken along the equator. These changes in air pressure and wind speed cause warm surface water to move eastward along the equator, from the western Pacific to the coast of northern South America. In turn, this weakens storms in the Atlantic.

Matthew Rosencrans, a meteorologist at the Climate Prediction Center, said the interplay between El Nino and conditions favorable to Atlantic storms, such as sea surface temperatures and this year’s wind patterns, create a rare contradiction.

“It’s kind of like a clash between those two big features,” he said. “El Nino can control about 33-38% of the variance. So it’s not all of it. The sea surface temperature in the Atlantic should stay around for months during the summertime once they are established. Overall, the patterns in the Atlantic that are favorable, they change in what we call ‘the Atlantic multidecadal oscillation.’ They change every 25-40 years. The specifics as far as how warm it is this year, we are warmer than we were last year. We’re about as warm as we were in 2020.”

It’s been almost 150 years since the first U.S. hurricane warning on Aug. 21, 1873 — when the U.S. Army Signal Corps warned of a hurricane threat to the East Coast from Cape May, N.J., to New London, Conn., by displaying signal flags along the coast. By 1935, the Weather Bureau (now the National Weather Service) was receiving observations from weather stations around the Caribbean Sea and in the Bahamas. It also received regular observation from ships via radio. By 1960, a radar fence was constructed along the Gulf and Atlantic coasts, and a radius of 200-250 miles was kept under surveillance. In 1961, the first weather satellite was placed into orbit.

Since then, technology has allowed for more accurate predictions, largely thanks to supercomputers. About four days before Hurricane Isabel arrived in September 2003, most weather models predicted the monster storm — which caused widespread flooding and damage to Hampton Roads — would make landfall between North Carolina and New Jersey.

1 of 23

Local resident Sean J. Fayhey, 46, looks out at the storm at the beachfront near Sanfiddler and Sandbridge Roads in the Sandbridge area of Virginia Beach Thursday afternoon, as the peak of Hurricane Isabel hits Hampton Roads. (photo shot on September 18, 2003. (MARTIN SMITH-RODDEN/THE VIRGINIAN-PILOT)

A lot of data goes into computer forecast models, and each one weighs factors — such as time of year and storm location — differently to try to come up with a prediction. These are often called “spaghetti plots,” and are often seen on TV. Each one is a little bit different, and forecasters look at the plots and try to get a consensus. If they’re all showing a similar path, there’s more confidence that a storm is going to be heading in a particular direction. Spaghetti plots are typically used in the short-term, about 1.5-2 days before landfall, and then the models start to split, because they’re all taking into account and weighing different factors.

The National Hurricane Center issued a hurricane watch from the North Carolina/Virginia border to Chincoteague about 50 hours before Isabel struck land. By 18 hours before the storm made landfall, the National Hurricane Center upgraded the watch to a hurricane warning for the entire coastline. Officials in Hampton issued Virginia’s first mandatory evacuation for Isabel on Sept. 17, about 35 hours before landfall. Eleven hours later, a mandatory evacuation was issued for some residents in Chesapeake, Norfolk and Virginia Beach, with a recommended evacuation for residents in Suffolk and Isle of Wight and York counties.

Breaking News

As it happens

Get updates on the coronavirus pandemic and other news as it happens with our free breaking news email alerts.

In more recent years, NOAA has made improvements to its forecasting systems. Specifically, since 2017, the administration has improved the lead time for short-term hurricane forecasts by two days. The seven-day track forecast now has the same accuracy as the five-day track forecast. The lead time of storm surge forecasts has also grown. The three-day event storm surge forecast today has the same accuracy as the previous two-day forecast.

“NOAA’s hurricane forecasts are more accurate than they’ve ever been. Based on advancements with our new hurricane model, reanalysis of forecasts for storms from 2020 to 2022 is shown that today, the accuracy of our forecast track has improved by 40% since 2017, and the accuracy of our forecasts’ intensity has improved by 46%,” Don Graves, deputy secretary of the U.S. Department of Commerce, said.

Despite the predictions, meteorologists agree that it only takes a single storm to create a “severe” or memorable hurricane season. Many remember the 1992 season as being particularly difficult, but most of that revolved around Hurricane Andrew, which was declared a Category 5. On paper, 1992 was a below-average hurricane season. Andrew, in mid-August, was the first named storm.

As the season progresses, weather experts will continue to encourage safety and preparation.

For tips on hurricane readiness and precautions, visit the weather page at PilotOnline.com. On Thursday, WTKR News 3′s First Warning Weather Team will share the biggest threats hurricanes pose to Hampton Roads and the Outer Banks. The half-hour special starts at 7:30 p.m.

Eliza Noe, eliza.noe@virginiamedia.com

Patrick Rockey, weather@wtkr.com