Conditions in the tropical Atlantic Ocean and the Caribbean Sea indicate 2017 could be an "extremely active season" for tropical storms and hurricanes, said NOAA on Wednesday.
The agency now says there is a 60 percent chance of an above-normal season, up from NOAA's May prediction of 45 percent, and 14-19 named storms, raised from the May forecast range of 11-17, and a slight increase of two to five major hurricanes.
"We are seeing signs this could be the most active season since 2010," said Gerry Bell, lead seasonal hurricane forecaster at NOAA's Climate Prediction Center, on a call with reporters on Wednesday.
For perspective, 2010 saw 12 hurricanes and 19 named storms total, a few of them severe.
The agency's overall expected number of five to nine hurricanes is unchanged.
A few dominant climate factors led forecasters to raise their expectations.
First, wind patterns across the tropical Atlantic region are all conducive to storm formation, including weaker vertical wind shear, weaker trade winds, and easterly winds coming off the coast of Africa.
Second, sea surface temperatures in the Atlantic are 1-2 degrees warmer than normal, raising the potential that there will be plenty of warm, moist air to fuel developing storms.
There are also lower chances of an El Nino forming, which means storm risk is higher, and so far, all of NOAA's predictive models are indicating a stronger than usual season.
NOAA said they have a "high degree of confidence these conducive conditions will persist," Bell said.
And the three-month period ahead is when the vast majority of storms — about 95 percent — occur.
There have already been six named tropical storms in the Atlantic in the first nine weeks of this year's season, double the number that typically form by this time in an average year.
There may very well be more to come.