WILLEMSTAD - Scientists are astonished by what is happening in the Caribbean Sea. The sea water temperature there is unusually high, currently reaching 29 degrees Celsius, as reported by the Belgian site hln.be. High sea water temperatures are a significant factor in hurricane development. At 29 degrees, the current temperature is 1.5 to 2.5 degrees above the normal level and almost 1 degree above the previous record.
Based on long-term forecasts, it is expected that these elevated temperatures may persist until October, with peaks in August and September. The increase in hurricane activity during the hurricane season, which runs from June 1 to November 30, is one of the possible consequences.
A year ago, in March 2023, high sea water temperatures began breaking records globally. Now, a year later, the water in the North Atlantic Ocean remains unprecedentedly warm. This could greatly influence the 2024 hurricane season. Despite the dampening influence of El Niño on North Atlantic hurricane activity, the extremely warm sea water in 2023 led to an above-average active hurricane season.
Formation
For hurricanes to form, several basic ingredients are necessary. First, a large low-pressure area, such as a cluster of thunderstorms, must move from Africa across the Atlantic Ocean.
If the sea water over which the thunderstorms travel is warmer than 26.5 degrees Celsius (the second ingredient), the warm sea water will evaporate and rise. At altitude, the warm air cools down, leading to the formation of more rain and thunderclouds.
The third basic ingredient is the Coriolis force. Due to the Earth's rotation, air in a low-pressure area does not flow directly to the center but around it. This effect is known as Buys Ballot's law.
At the equator, the Coriolis force is zero, preventing thunderstorms there from spinning and thus hindering hurricane formation. This explains why far fewer hurricanes pass by Aruba, Curaçao, and Bonaire compared to Saba, Sint-Eustatius, and Sint Maarten. The Leeward Islands are closer to the equator.
The fourth and final basic ingredient for hurricanes is that the wind speed and direction at sea level must be approximately the same as those at higher altitudes at the top of the storm. In other words, vertical wind shear must be low.
A forming hurricane needs to remain roughly intact vertically to extract the most energy from the warm sea water. If the wind at higher altitudes blows harder or in a different direction than at sea level, the hurricane gets blown apart.
Hurricane Season
The 2023 hurricane season was above average with twenty named tropical storms, seven hurricanes, three of which were major hurricanes (category 3 or higher). This was surprising because El Niño typically results in less hurricane activity due to increased vertical wind shear. High sea water temperatures played a crucial role in the heightened hurricane activity.
Currently, sea water temperatures are extremely high, and there is a significant chance that the situation will shift to La Niña later this year, which enhances hurricane conditions. The long-term forecast for this year predicts an exceptionally active hurricane season with twenty named tropical storms and nine hurricanes, four of which are expected to be major.