Catagory 5 Hurricane Dorian
Introduction
During the 2023 hurricane season, a strong El Niño event had significant effects on the Azores-Bermuda Ridge, leading to a weakening of this high-pressure system. As a result, surface winds, especially in the tropical Atlantic, decreased. This reduction in surface winds had several consequences, including unusual sea surface warming due to decreased ocean mixing and evaporation. Additionally, other factors, such as a strong Atlantic Multi-decadal Oscillation (AMO), reduced sulfate particles from cleaner shipping fuels, the Hunga-Tonga volcanic eruption, and lower levels of African dust, may have contributed to the overall climate conditions.
June 2023 Surface Pressure Anomaly
In this analysis, I will explore the transition from El Niño to La Niña and its potential impact on the 2024 hurricane season.
La Niña and Wind Shear
El Niño to La Niña Transition
Currently, El Niño is weakening rapidly, and meteorologists anticipate the development of a La Niña event by the main 2024 hurricane season. La Niña is characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. Just how will this transition affect the Atlantic hurricane environment?
Wind Shear and Tropical Cyclones
During La Niña events, wind shear in the tropical Atlantic typically decreases. Wind shear refers to the change in wind speed and direction with altitude. Reduced wind shear creates favorable conditions for the development and intensification of tropical cyclones. With weaker wind shear, disturbances in the tropics can organize more effectively, potentially leading to stronger storms.
The Strengthened Azores-Bermuda Ridge
Trade Winds and Storm Paths
La Niña tends to strengthen the Azores-Bermuda Ridge, a high-pressure system located in the North Atlantic. As this ridge strengthens, trade winds increase. These trade winds play a crucial role in steering tropical cyclones. Here’s how:
- Westward Movement: A stronger Azores-Bermuda Ridge tends to steer Atlantic tropical cyclones farther west. This westward shift increases the risk of landfalls in regions such as the Caribbean, the US East Coast, and the Gulf Coast.
- Trade Wind Enhancement: Stronger trade winds enhance ocean surface mixing. This process involves cooler water from deeper ocean layers rising to the surface. Consequently, the sea surface temperatures may gradually cool during the hurricane season.
- Evaporation and Moisture Transport: The intensified winds also lead to increased evaporation and moisture transport. This contributes to further cooling of the sea surface.
Azores-Bermuda Ridge controls Tropical Cyclone Tracks
Sea Surface Temperature Anomalies
Outlook for 2024
Given the current very high sea surface temperature anomaly in the tropical North Atlantic, it is likely to remain above normal as we move into the peak of the 2024 hurricane season. However, the strengthening La Niña and the associated changes in wind patterns may gradually mitigate this anomaly.
Tropical North Atlantic Sea Surface Temperatre Anomaly
In summary, the transition from El Niño to La Niña could significantly influence the behavior of tropical cyclones in the Atlantic. If the Azores-Bermuda Ridge strengthens during this hurricane season we can expect an increased risk of tropical cyclone landfalls in regions such as the Caribbean, the US East Coast, and the Gulf Coast. As wind shear decreases, tropical cyclone frequency and intensity can increase so it will be essential to stay informed about the evolving conditions and their potential impact on hurricane activity.
