Atlantic hurricane activity is likely to exceed average levels this season, increasing the risk a major storm will hit the US coastline, according to a revised prediction by Colorado State University forecasters.

Declining odds of a major El Nino climate event and warm ocean temperatures in the tropical and subtropical Atlantic have caused the forecasters to flag above-average activity after earlier in the year expecting a more benign season.

“With the increase in our forecast, the probability for major hurricanes making landfall along the United States coastline and in the Caribbean has increased as well,” Philip Klotzbach and Michael Bell said.

The forecasters expect a total of eight hurricanes and 15 named storms, up from a June 1 forecast for six hurricanes and 14 storms. In April they expected four hurricanes and 11 named storms.

The probability of a US major hurricane landfall this year is about 120% of the long-period average, the Colorado forecasters say.

The US National Oceanic and Atmospheric Administration also anticipates an above-normal season, which runs from June through to November 30.

Last year was the most active season since 2012 with 15 named storms including seven hurricanes and four major hurricanes.