Hurricane Danny is the first Atlantic hurricane of the season

A relatively compact Danny strengthened to a Category 1 hurricane on Thursday morning, still more than 1,000 miles east of the eastern Caribbean islands.

Plenty could change in the next few days, but it looked Thursday as if the storm could reach the Leeward Islands such as Guadeloupe and St. Kitts and Nevis as a Category 1 hurricane by Monday, CNN meteorologist Dave Hennen said.

Danny was small for a hurricane, the National Hurricane Center said, with hurricane-force winds extending only 10 miles from center. Its maximum sustained winds were 75 mph, just above the hurricane threshold, Thursday morning.

They strengthened to 80 mph by Thursday afternoon and are expected to strengthen more over the next 24 hours, before weakening.

The hurricane center cautioned that Danny’s small size make forecasting its strength especially difficult.

“Danny’s compact size makes it subject to significant fluctuations in strength, both up and down, and such fluctuations are notoriously difficult to forecast,” the center said in a forecast discussion posted online.

El Niño’s effect on hurricanes

Danny two days earlier became the first named storm of the Atlantic season — unusually, if not unexpectedly, late.

Forecasters had already said that this year’s season would produce a below-normal number of hurricanes, in part because of this year’s strong El Niño, which is causing strong wind shears in the Atlantic, hindering cyclone development.

Hurricane Arthur, a Category 2 storm, was the last hurricane to make landfall in the United States, when it came ashore last July between Cape Lookout and Beaufort in Emerald Island, North Carolina, the National Hurricane Center said.

This has been the longest stretch of time to pass without a major hurricane hitting the United States since reliable record keeping began in 1850, a 2015 NASA study said.

Though forecasters are calling for a below-average storm season in the Atlantic, CNN’s Hennen said any hurricane that does emerge this year can have a strong impact.

Hurricane Andrew struck South Florida and south-central Louisiana in August 1992 with 175-mph winds, wiping out entire communities, killing 23 people and causing more than $25 billion in damage.

According to the National Oceanic and Atmospheric Administration Climate Prediction Center, which has updated its 2015 Atlantic Hurricane Season Outlook, there is a 90% chance of a below-normal hurricane season and a lower chance of expected storm activity in the United States this year.

This means that of the 6 to 10 named storms for this season, 1 to 4 storms are likely to become hurricanes in 2015.

And there’s an even smaller chance that one of these storms will transform into a major hurricane. The National Hurricane Center calls any Category 3 or higher storm a major hurricane.

Also, the Atlantic Ocean has had much cooler temperatures, which decreases the chances of major storm activity.

Since 1995, the United States has been in a high hurricane activity area, which typically lasts around 25 years. But for almost a decade, the country hasn’t seen a hurricane greater than a Category 3 storm, putting it in a nine-year hurricane “drought.”

The United States still has seen some big storms in the past few years. In 2012, hurricane-turned-cyclone Superstorm Sandy, ravaged the Northeast with damaging flooding and powerful winds.