Atlantic hurricane season update – 2023

 

A busy tropical Atlantic (Source: NOAA)

The Atlantic hurricane season spans six months of the year from June – November.  NOAA recently released its August update to its seasonal hurricane forecast.

It calls for an above average Atlantic hurricane season with 14 – 21 tropical storms (sustained winds 39 – 73 mph), of which 6 – 11 become hurricanes (74 mph or greater), including 2 – 5 major hurricanes (Category 3 or greater with sustained winds of at least 111 mph).  That’s a significant increase from their original June forecast that called for 12 – 17 storms, 5 – 9 hurricanes, with 1 – 4 major hurricanes. 

 

Making NOAA’s forecast particularly unique is the unusual set of environmental conditions that exist.  NOAA’s Climate Prediction Center said on August 10: “El Niño is anticipated to continue through the Northern Hemisphere winter (with greater than 95% chance through December 2023 -February 2024).”  El Nino conditions correlate with lower than average sea surface temperatures in the tropical Atlantic, combined with an above average amount of wind shear.  Both create less favorable conditions for tropical storm formation.

However, despite the presence of El Nino, much of tropical Atlantic has unusually warm sea surface temperatures.  According to Colorado State University hurricane expert, Dr. Philip Klotzbach, “Most of the tropical and subtropical Atlantic remains near or at record warm levels, favoring Atlantic #hurricane activity.”  Traditionally, the presence of El Nino has correlated to average or below average tropical development in the Atlantic such as during the 1982, 1997 or the 2015 seasons. 

That’s what makes NOAA’s updated forecast for an above average season so unusual.  Despite El Nino becoming more pronounced during June and July, NOAA increased the number of tropical storms and hurricanes they expect this season.  Their scientists expect that the warmth of the Atlantic will offset, at least to some extent, the El Nino conditions.

Before yesterday, there were only five storms in the Atlantic so far this season.  There was an unnamed subtropical storm in January, along with three tropical storms and a short-lived Category 1 hurricane as of July 24.  However, over the last 24 hours the National Hurricane Center has been tracking three tropical storms (Emily, Franklin and Gert) and a tropical disturbance in the Gulf of Mexico that could develop further. 

September is the busiest month of the hurricane season, so it makes sense the tropics have become more active in late-August.  That’s exactly what NOAA was expecting when they issued their updated forecast for above average activity.

Last season the Atlantic had three November hurricanes illustrating how the tropics can remain active until late in the season.  That’s unusual, though, as environmental conditions normally become less favorable in late-October with cooler waters and higher levels of wind shear.  Hurricane season runs through November 30.