2019 Hurricane Outlook for the Atlantic Ocean

NOAA released its 2019 forecast for the hurricane season that begins June 1 in the Atlantic Ocean.  It calls for a near average hurricane season with 9 – 15 tropical storms, 4 – 8 hurricanes and 2 – 4 major hurricanes.  An “average” Atlantic hurricane season features 12 tropical storms, 6 hurricanes and 3 major hurricanes.  A tropical storm has sustained winds around its center of 39 – 73 mph while a hurricane has sustained winds of 74/+ mph.  A hurricane becomes “major” when it reaches Category 3 intensity on the Saffir-Simpson Hurricane Wind Scale with sustained winds of at least 111 mph.

On May 9, NOAA’s Climate Prediction Center issued an “El Nino Advisory” and expects a high chance that El Nino will continue through the summer and into the fall.  That’s a large factor NOAA considered in its seasonal hurricane forecast.  That’s because El Nino conditions, characterized by a warming of the equatorial Pacific Ocean, have worldwide repercussions.  Most notably, during moderate to strong episodes of El Nino, conditions in the tropical East Pacific (off the west coast of Mexico) are more favorable for tropical storm development.  

Conversely, during El Nino years conditions in the Atlantic Ocean tend to be less favorable for tropical storm development with cooler than average sea surface temperatures and an increased amount of wind shear.  Hurricanes typically require warm ocean water of sufficient depth, commonly 80° Fahrenheit to a depth of 200’, to develop.  They also require little or no wind shear (differing wind speed and direction with altitude) for the hurricane circulation to intensify.  In issuing its forecast, NOAA cited above average ocean temperatures in the tropical Atlantic Ocean and Caribbean Sea as well as a more active West African monsoon.  Both of these factors are known to favor a more active Atlantic hurricane season.

The last moderate or strong El Nino occurred in 2015-2016.  The 2015-2016 El Nino was one of the strongest on record, comparable to the 1982-1983 and 1997-1998 episodes.  These three major El Nino events all had discernible impacts on the Atlantic hurricane season.  While the 1982 (6, 2, 1) and 1997 (8, 3, 1) Atlantic hurricane seasons were much quieter than average, the 2015 season was closer to, but still below average with 11 tropical storms, 4 hurricanes and 2 major hurricanes.

By comparison, weak episodes of La Nina made weather headlines in 2016-2017 and 2017-2018.  Consequently, the 2016 and 2017 Atlantic hurricane seasons were busier than average.  A total of 17 hurricanes and 10 “major” hurricanes developed during these two seasons, above the two year average of 12 and 6.  Three Category 5 hurricanes also developed, including Matthew (2016), Irma (2017) and Maria (2017).  Fortunately, none of them made landfall at that intensity but were each deadly and destructive.  Despite the weak El Nino that developed last year, the 2018 Atlantic hurricane season was still an active one with 15 tropical storms, 8 hurricanes and 2 major hurricanes.  Hurricane Michael developed last season and became only the fourth Category 5 hurricane on record to make landfall in the United States. 

It’s important to remember that a hurricane season does not have to be an active one for an intense or destructive hurricane to develop.  The 1992 Atlantic hurricane season comes to mind that occurred during a strong episode of El Nino.  Consequently, it was a below average hurricane season with only 7 tropical storms, 4 hurricanes and 1 “major” hurricane.  However, that one hurricane was Andrew which made landfall in Florida as a Category 5.  It was the first Category 5 to make landfall in the United States since Camille in 1969 and would remain the costliest natural disaster in US history until 2005.  The next tropical storm that develops in the Atlantic Ocean will be named “Barry.”