What does the 2023 Atlantic hurricane season forecast mean?

The 2023 hurricane season officially begins today, and the experts at NOAA have weighed in with their thoughts on what to expect. The picture is murky, with NOAA predicting almost equal odds of the season being near normal, above normal, or below. 

Graphic courtesy of NOAA

However, NOAA does provide ranges for the number of named storms, hurricanes, and major hurricanes to expect, and all of those numbers are near the long-term average. The numbers are similar to those issued by the team of hurricane season forecasters at Colorado State, who now annually dedicates their forecast in memory of legendary tropical expert Dr Bill Gray. The deterministic CSU forecast is on the low end of NOAA's ranges. Not everyone agrees that this year will feature near or below average tropical development (we see you, UK Met office), but it is the predominant opinion.

The developing El Niño in the equatorial Pacific is expected to play a role in suppressing hurricane development this summer. Since El Niño increases wind shear (especially speed shear) in the critical zone for tropical development in the Caribbean, ENSO positive hurricane seasons tend to have fewer storms. Dry Saharan air and/or dust can impede storm development as well. ENSO's phases can have a downstream impact on trade winds in the Atlantic Ocean, which in turn increases or decreases the wind that blows dust off the Sahara and into the hurricane development zone. 

Impacts of El Niño from June through August.
Graphic courtesy of NOAAClimate.gov

It's important to remember that a seasonal forecast does not provide any insight to the number of storms that will make landfall in a given year. CSU's forecast does offer some guidance on the likelihood of landfall by state, but that forecast is largely based on climatology, not weather. The infographic below shows all the locations where hurricane conditions have been felt on the Atlantic coast since 1950, and it's an example of the type of information CSU uses to create their landfall probability guidance. 

If the above graphic got your wheels turning, here are some noteworthy facts about storms in the Atlantic Basin:

- Statistically speaking, the hurricane season peaks around September 10th. The season officially ends on November 30th, but the number of tropical cyclones rapidly declines after the September 10th peak, and storms can (and do) form in December and beyond. 

- More storms beginning with the letter "I" have had their names retired than any other letter. Since 1954, when the naming convention became official, 13 "I" named storms have been retired. The latest "I" name to be added was 2022's Ian. 

- In the entire 69-year history of named tropical storms, only one name, Allison, was retired without the storm ever reaching hurricane status. Despite the lack of wind, experts decided to retire Allison because of the devastating floods that it caused, especially in the Houston metro area, in 2001.

- Speaking of named storms, in 2021 the WMO ended the practice of using Greek letters for named storms when the alphabetical list is exhausted. Instead, a perennial list of supplemental names will be utilized. The last time we ran out of names on the alphabetical list was in 2020, when a record-breaking 30 tropical storms were named.

- The 2005 season does not hold the record for named storms, but it's the year with the most storm names retired. In addition to Katrina, the deadliest hurricane in US history, the names Dennis, Rita, Stan, and Wilma were also removed from the rolls. 

- On average, the first named storm of the season forms in June, but one of the most notorious hurricanes in American history, Andrew, was the first named storm of 1992. Andrew did not become a Tropical Storm until August 16th, making it one of the latest "first storms" of a single season, and one of only four Category 5 hurricanes to make landfall in the United States.