An updated Colorado State University (CSU) forecast predicts 18 named storms, nine hurricanes and four major hurricanes during the Atlantic hurricane season. 

CSU says the revised forecast is an increase from the 15 named storms, seven hurricanes and three major hurricanes they predicted on June 1. An updated forecast will be released on August 4. 

Researchers say an above-average Atlantic hurricane season is predicted because of record warm sea surface temperatures in most of the tropical and subtropical Atlantic. The Atlantic basin hurricane season runs from June 1 to November 30 with most activity occurring between mid-August and mid-October 

But researchers say there is more uncertainty than usual with this outlook because of conflicting signals between much warmer than normal Atlantic waters and an expected robust El Nino for the peak of the hurricane season.  

“El Nino increases vertical wind shear in the Caribbean and tropical Atlantic, which can tear apart storms as they form, but the extreme anomalous warmth in the Atlantic may counteract some of the typical El Nino-driven wind shear,” CSU says. 

Long-term seasonal averages are 14 named storms, seven hurricanes and three major hurricanes. The researchers estimate the probability of a major hurricane making landfall in the United States to be above the long-term average.   

CSU uses 25-40 years of historical hurricane seasons to evaluate conditions, including Atlantic sea surface temperatures, sea level pressures, vertical wind shear levels, El Nino and other factors in its modelling.  

This is the 40th year that the CSU hurricane research team has issued an Atlantic basin seasonal hurricane forecast.  

The CSU forecast is not an exact measure but a “best estimate” of activity in the Atlantic during the upcoming season