Quiet start to Atlantic hurricane season
The 2019 Atlantic hurricane season, which began on June 1, has been relatively quiet, with only two named storms through the middle of August.
Four tropical storms had formed by this time last year. In 2017, Harvey developed on Aug. 17, marking the eighth system of the season, dumping prolific rains on Southeast Texas a week later.
Infamous late August hurricanes such as Katrina (2005) and Camille (1969), and Connie and Diane (1955), brought devastating coastal and inland flooding to parts of the U.S.
Hurricane season in the Atlantic basin peaks on Sept. 10, so increased activity is likely. The key ingredient is warm water, which takes longer to heat up than land.
Among the reasons for a quiet season in 2019 is El Nino — officially over now — that creates stronger winds around the equator east of South America, which is unfavorable for thunderstorm organization in the tropical Atlantic.
A Saharan Air Layer more extensive than usual has a drying influence that inhibits tropical waves from intensifying coming off the coast of West Africa.
The Accumulated Cyclone Energy (ACE index), which reflect the total energy output of tropical systems globally, is slightly above normal, despite low values in the North Atlantic. (The North Indian basin is highly energetic currently.)
The Atlantic hurricane season is still in its early stage, with on average 80 percent of the activity yet to come after Aug. 15. But indications are little development will occur during the latter half of the month.