Santo Domingo—The 2024 hurricane season is active. Meteorologists are monitoring Hurricane Beryl. According to the latest report from the National Hurricane Center (NHC), it will reach the Windward Islands this Sunday and is expected to intensify rapidly.
“A tropical cyclone is a low pressure that forms at a tropical latitude – close to the equator, but never at the equator – that has a defined and organized surface circulation (in the northern hemisphere it rotates counterclockwise).” This is how the U.S. National Oceanic and Atmospheric Administration (NOAA) defines it.
These systems can cause catastrophic damage in the Atlantic with strong winds, torrential rains, and storm surges. Understanding how these natural giants form is crucial to improving preparedness and response capabilities.
The process of tropical cyclone formation generally begins as a tropical disturbance, an area of low pressure that can form from tropical waves moving westward from the coast of Africa. These tropical waves are areas of meteorological activity that can generate convection, creating storms that, under the right conditions, can develop an organized circulation.
When a tropical disturbance has a closed circulation of well-defined winds and storms, it becomes a tropical depression. At this stage, winds are less than 63 kilometers per hour (39 miles per hour). If winds increase and reach between 39 to 73 miles per hour (63 to 118 kilometers per hour), the system is classified as a tropical storm and is given a name. When winds exceed 119 kilometers per hour (74 miles per hour), it is classified as a hurricane.
NOAA explains on its official website that for a tropical cyclone to form, several atmospheric and marine conditions must be met, including a specific ocean temperature and specific winds.
Temperature and humidity
The U.S. National Oceanic and Atmospheric Administration explains that for it to form, “ocean waters must be 80° Fahrenheit at the surface and warm to a depth of 150 feet because warm ocean waters feed the heat engines of tropical cyclones.”
In addition, according to the entity, they need an atmosphere that cools fast enough with increasing height so that the difference between the top and bottom of the atmosphere can create storm conditions.
A moist mid-troposphere (3 miles high) is also needed because dry air ingested in thunderstorms at the mid-level can kill circulation.
Gyre and location.
NOAA indicates that conditions must be ripe for the Coriolis force to act, which causes winds converging toward a low pressure to rotate, creating the cyclone’s characteristic spiral pattern.
“The storm must be at least 300 miles from the equator for the Coriolis force to create the spin. This force causes hurricanes in the northern hemisphere to spin counterclockwise, and those in the southern hemisphere to spin clockwise. This gyre may play some role in helping tropical cyclones organize themselves,” the U.S. agency notes.
Wind
Wind shear plays a crucial role. If the shear is high, it can disorganize the storm by dispersing the heat and moisture needed for intensification. “Low vertical wind shear (the change in wind speed and direction with height) between the surface and upper troposphere favors thunderstorm formation, which provides the energy for tropical cyclones. Too much wind shear will disrupt or weaken convection,” NOAA points out.
According to the entity, fulfilling these conditions is necessary but insufficient since many disturbances with favorable conditions do not develop.