Forecasters see the possibility of as many as five major storms over the coming three months.
Government forecasters said Wednesday that the Atlantic hurricane season, already a busy one, may be the busiest since 2010 and is likely to produce two to five major hurricanes.
“There’s a possibility that the season could be extremely active, ” said Gerry Bell, the lead seasonal hurricane forecaster with the Climate Prediction Center, a division of the National Oceanic and Atmospheric Administration. In all, he said, the center was forecasting 14 to 19 named storms, with winds of 39 miles per hour or higher, including five to nine hurricanes.
Major hurricanes are defined as Category 3 and above, with sustained winds of 111 m.p.h. or higher.
The hurricane season, which runs from June through November, has already been active, with six named tropical storms. The latest, Franklin, is expected to reach hurricane strength Wednesday night, Dr. Bell said, with winds above 73 m.p.h., before making landfall in the Yucatán Peninsula in Mexico.
But the season normally is most active from August through October, which is why the National Oceanic and Atmospheric Administration offers a midseason update each year.
In May, Dr. Bell and his team forecast an above-normal season, with 11 to 17 named storms and as many as four major hurricanes. In a typical year, the Atlantic will have 12 named storms and three major hurricanes. The 2010 season was exceptional, with 12 hurricanes, including five major ones, among 19 storms.
Dr. Bell said that as the season has progressed, the forecast has become more confident, with a 60 percent likelihood that the season will be above normal, compared with 45 percent in May. The likelihood of a below-average season is now only 10 percent, down from 20 percent.
Dr. Bell said conditions that were predicted before the season have developed and are likely to persist. Those include warmer-than-average ocean temperatures, which add energy to storms, and weaker-than-average trade winds and wind shear. Adding to the confidence is that there is even less likelihood that El Niño will develop. El Niño can result in wind shear, which disrupts storms as they develop.
The forecasters made no predictions about whether storms may make landfall or whether they would track into the Gulf of Mexico or along the Atlantic coast. Storm direction is affected by the weather patterns in place as the storm develops and moves. Those are predictable only five to seven days in advance, Dr. Bell said.
But usually, he said, in a more active season more storms form farther south, in the tropical Atlantic. “Those are storms that typically track further westward, ” he said. “They’ re also in conducive conditions for longer, so they have a greater chance of becoming hurricanes.”
