The past few weeks have seen an incredible burst in Tropical Activity in the Atlantic Ocean Basin. At one time in August, there were 5 Tropical Systems in the Atlantic, which was followed by the rapid intensification of Category 4 Hurricane Idalia as it hit Florida in late August. The National Hurricane Center was originally predicting a near-average Hurricane Season during their early May outlook. However, they have significantly increased their predictions for a major season in their August outlook.
The August Outlook was issued on August 10th, calling for yet another above-average season. The predicted ranges of activity are 14-21 named storms (Tropical Storms and Hurricanes), of which 6-11 are predicted to be hurricanes, and of those 2-5 are predicted to be major hurricanes (Category 3 or higher).
These increased odds for an active hurricane season are mostly due to the weather conditions that have caused active seasons since 1995 remaining in place. These conditions include weaker trade winds, weaker shear in the Mid-Atlantic, and active monsoon seasons in West Africa. Wind shear is a difference in wind speed or direction at different altitudes, and high wind shear can displace warm air above the center of a hurricane, weakening it considerably. Since this factor is weaker over the area where hurricanes tend to develop, Tropical disturbances will have an easier time intensifying. Additionally, active monsoons in West Africa have sent a large number of Tropical disturbances out into the Atlantic, and it is these disturbances that will eventually strengthen and head towards the Caribbean and then the US.
The largest factor which could suppress hurricane development this year is an active El Nino. This condition is one of 3 climate conditions that could exist due to the temperature in the Pacific Ocean, the other 2 being ENSO-Neutral and a La Nina. La Nina conditions are typically the best contributors to tropical development in the Atlantic, and El Nino the worst, as during a El Nino, wind shear in the West Atlantic is increased. However, the usual impacts of an El Nino have been slow to reach the Atlantic, and thus what would normally be a weakening factor for Tropical development isn’t having its usual effect.
Of course, the NHC’s Outlook is just a prediction, but if the patterns of the last few years are anything to show, more Tropical Storms and Hurricanes are likely to come from the Atlantic. A “quiet” Hurricane season hasn’t happened since 2015, which was also the last year that no Tropical system made landfall in the US. Remember, Hurricane season lasts from the beginning of June until the end of November, so Idalia may not be the end of 2023’s Hurricanes.
