Hurricane season is underway, but so far, only the Pacific Ocean is showing activity.
In the Eastern Pacific, we have seen the formation of Hurricane Barbara and Tropical Storm Cosme, and forecasters are tracking Tropical Depression 4 and a potential areas of development.
That said, it’s 13 days into the Atlantic season, and we have yet to see any significant areas of development this year in the Atlantic or Gulf. In fact, there has been only one potential area of interest in the Atlantic, an upper-level low that held only a small chance of attaining tropical characteristics.
It is typical for the Eastern Pacific to become active earlier than the Atlantic. It’s a combination of a few factors, including higher ocean surface water temperatures and more favorable winds earlier in the year.
And it is not unusual to have little activity in June in the Atlantic basin, even in what is expected to be an above-average year. In fact, the Eastern Pacific hurricane season is considered to begin two weeks earlier, May 15.
As the Eastern Pacific becomes more active, elsewhere in the Pacific, it’s been an unusually quiet start to tropical season.
The Northwest Pacific hurricane basin, which includes typhoons that impact Japan, is off to one of the slowest starts in more than 50 years. On Wednesday, Wtip became the first storm to reach tropical storm strength - the latest to form in the Western Pacific since 1984.
The Pacific typhoon season averages about 25 storms per year, with most occurring between June and October.
There is no singular reason for the unusually slow start to the Western Pacific season. In the Pacific, we are in a neutral ENSO phase, meaning we are between an El Niño (observed in 2024) and La Niña.
ENSO, or El Niño-Southern Oscillation, is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific. During a neutral phase, sea surface temperatures are generally close to average.
Other years with a similarly slow start to the Western Pacific season were in years that transitioned to La Niña after a strong El Niño, which is not a good match for the neutral ENSO. Some possible reasons for lack of storms developing in the Western Pacific include an increase in atmospheric shear in the past several weeks.
