It only takes one. Just ask the survivors of Superstorm Sandy or Hurricane Katrina.

Colorado State University, which pioneered seasonal storm forecasting 36 years ago, on Tuesday upped the ante for named storms in the Atlantic by one to 14 before the six-month Atlantic season ends on Nov. 30. The school offers four major forecasts a year, with the first coming in April.

Atlantic hurricanes and tropical storms are some of the most closely watched weather systems in the world because, aside from the human calamity, they can disrupt oil, natural gas and agriculture markets, as well as threatening expensive coastal real estate. The season began June 1.

“As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them,” said Phil Klotzbach, the forecast’s lead author. “They should prepare the same for every season, regardless of how much activity is predicted.”

This year’s forecast is tricky because models are mixed on whether an El Nino across the equatorial Pacific will last into late August and September, Klotzbach said by telephone. Of the 14 named storms, six could be hurricanes and two major systems with winds of 111 miles (179 kilometers) per hour or more, according to the report.

Along the U.S. Gulf and Atlantic coasts, $1.8 trillion of real estate and 7.3 million homes are at risk, according to CoreLogic, a property risk firm based in Irvine, California. In addition, the Gulf Coast accounts for roughly 45% of U.S. refining capacity, while 17% of the nation’s crude comes from the Gulf of Mexico. Florida is the world’s second-largest orange-juice producer.

Superstorm Sandy caused $65 billion in damage and killed 72 people in the U.S., according to the National Hurricane Center. Katrina caused $125 billion in damage and killed at least 1,800.

What happens in the Pacific may seem far removed from the Atlantic. But El Nino can cause wind shear to develop there that can rip apart budding tropical storms and hurricanes. In recent weeks there have been indications El Nino could weaken, but Klotzbach said he believes it will last into August.

August is crucial because the heart of the Atlantic season beats more forcefully around the 20th of the month and continues through early October, with some of the worst storms arriving in September. During this time, weather systems coming off Africa can draw warm Atlantic water and explode into some of the most destructive hurricanes on record.

Cabo Verde

It is the storms that originate near Cabo Verde that most seasonal forecasts are trying to predict.

In May, the U.S. National Oceanic and Atmospheric Administration predicted nine to 15 storms would be named in 2019, with 4 to 8 becoming hurricanes and 2 to 4 growing into major systems with winds of 111 miles per hour or more. A storm gets a name when its winds reach 39 mph and becomes a hurricane when they get to 74 mph.

Last year, Colorado State predicted 14 named storms in June and 15 were observed. From 2015-2017 the June forecast also underestimated the number of total storms.