The mighty trade winds that ushered ships across the Atlantic when sails and Mother Nature set maritime agendas gave way in 2015 to the westerlies — gales that pile warm Pacific Ocean water against the Americas and signal El Nino.
But like a pendulum, that water will slosh back toward Asia. Trade winds will regain power. The subtropical jet stream that helped kill Atlantic hurricanes will shift south.
And La Nina will awaken.
Just as El Nino helped protect Florida from tropical cyclones this storm season, hurricane experts are already considering the fate of the U.S. coast in a La Nina year, which 2016 could easily become.
“After a really big El Nino, you seem to transition to La Nina, and it can happen rapidly,” said Bill Patzert, a climatologist at NASA’s jet propulsion laboratory in Pasadena, Calif. “The 2015 hurricane season was somewhat benign in the Atlantic, but if La Nina kicks in this coming summer, it could go back to spectacular.”
El Nino works as a hurricane deterrent by using the subtropical jet stream to cut the tops off storms with strong vertical shear — winds moving at different speeds and directions in different levels of the Atmosphere. The eastern Pacific Ocean is warmer than normal as surface waters flow west.
La Nina is marked by strong winds from the east that push warm Atlantic waters toward the U.S., while weaker winds from the west are less able to disrupt storms. The eastern Pacific Ocean is cooler than normal as east winds push surface water toward Asia.
During neutral years – between La Nina and El Nino – ocean temperatures, tropical rainfall patterns and wind patterns are closer to long term averages.
“It’s certainly possible that La Nina could be in place by late autumn (2016), which would favor an active Atlantic hurricane season,” said Bob Henson, a meteorologist and blogger for WeatherUnderground. “The closer we are to La Nina, the more favorable it is for hurricanes to develop in the Atlantic.”
Read more about what the experts think of the 2016 hurricane season here.