(CNN) -- Hurricane season officially began Wednesday, with forecasters saying it's likely to be an above-average season.
Colorado State University's Tropical Meteorology Project predicts many as five major hurricanes could form over the Atlantic Ocean. The university predicts 16 named storms and a total of nine hurricanes.
The National Oceanic and Atmospheric Administration (NOAA) outlook is for 12 to 18 named storms, six to 10 hurricanes and three to six major hurricanes.
Hurricanes are categorized by the Saffir-Simpson Hurricane Wind Scale, a 1-to-5 categorization based on the storms's intensity. Storms are classified as Category 1 hurricanes when wind speeds top 74 mph. The scale goes up to Category 5, with sustained wind speeds greater than 155 mph.
A named storm has winds of 39 mph or higher, and major hurricanes are those in categories 3, 4 or 5 -- with winds of 111 mph or higher.
This could be an above-average season, said NOAA's Jane Lubchenco, a marine ecologist and environmental scientist.
"The United States was fortunate last year. Winds steered most of the season's tropical storms and all hurricanes away from our coastlines," Lubchenco said. "However, we can't count on luck to get us through this season. We need to be prepared, especially with this above-normal outlook."
NOAA said among the factors leading to the above-average season is warm Atlantic water. Sea surface temperatures in areas where storms are likely to form are up 2 degrees Fahrenheit from average temperatures, NOAA said.
The Atlantic hurricane season begins June 1 and ends November 30.