A La Niña pattern now appears much more likely to develop this summer and fall, potentially exacerbating the active Atlantic hurricane season already expected. That comes from Dr. Gerry Bell, lead scientist of NOAA’s Seasonal Hurricane Outlook Team since 1998, on a conference call Thursday morning.
The official NOAA forecast for the 2020 Atlantic hurricane season already calls for above-normal tropical activity with 13-19 named tropical storms, 6-10 hurricanes, and 3-6 major hurricanes. A typical season brings 12 tropical storms, 6 hurricanes and 3 major hurricanes (category 3 or stronger). That forecast was made in the anticipation of a neutral El Niño Southern Oscillation pattern — neither El Niño nor the opposite, La Niña.
In the last several weeks, sea surface temperatures and upper-ocean heat content in the equatorial Pacific have cooled dramatically and unexpectedly. This is shifting forecast models toward a higher likelihood of a La Niña pattern developing during the coming hurricane season.
La Niña patterns, featuring cooler than normal ocean temperatures in a certain section of the equatorial Pacific, act to enhance Atlantic hurricane season by decreasing wind shear over the tropical Atlantic. This makes the background environment more favorable for any given storm to form and intensify.
Dr. Bell says this could tilt to scales “toward the upper end” of their forecast ranges given for the coming hurricane season, and potentially lead to an extremely active season. Stay with the First Warning Weather team for updates as Atlantic hurricane season begins on Monday, June 1.