Why hurricanes very rarely cross the equator and why it is extremely difficult for them
Hurricanes, according to scientific research, have a strange feature – they very rarely cross the equator. Although isolated cases of such a crossing have been recorded (for example, Cyclone Agneta in 1985 and Cyclone Joan in 1989), this remains an extremely rare occurrence. This geographical phenomenon is of interest to meteorologists and climatologists. The reasons for this phenomenon are deeply rooted in the physical and atmospheric laws operating in the tropical regions of our planet, informs Ukr.Media.
Origin of hurricanes
First, it's important to understand how hurricanes form and why the equator is such a difficult barrier for them to cross. Understanding this process is an important step toward unlocking the mystery.
Hurricanes, including typhoons and cyclones, are formed by the interaction of many factors, among which ocean water temperature plays a key role. Warm tropical waters are considered the ideal base for the birth and development of hurricanes.
When the ocean surface warms to at least 26.5 degrees Celsius, the process of active evaporation begins, water vapor rises into the atmosphere, creating a zone of increased humidity and heat. Such conditions contribute to the rise of heated air upward and the formation of clouds. Temperatures of 30°C and above create particularly favorable conditions, but are not necessary for the formation of a tropical cyclone.
And this is where physical dynamics come into play. In the tropics, air moves vertically, rising to high-pressure atmospheric layers, but at the equator this vertical circulation cannot turn into rotational motion due to the absence of the Coriolis effect.
The Coriolis effect, caused by the planet's rotation, causes air flows to deviate to the left in the Northern Hemisphere and to the right in the Southern Hemisphere—this physical fact is key to explaining why tropical storms rarely cross the equator. Right at the equator, the Coriolis effect becomes zero, which prevents the development of the stable rotational circulation necessary for hurricane formation and strengthening.
The laws of nature as a complex obstacle
Hurricanes, as majestic meteorological phenomena, obey the laws of nature that determine their characteristics and behavior. These phenomena are just one of many in which the Earth demonstrates its fundamental physical principles.
To understand why hurricanes rarely cross the equator, one must look into the world of atmospheric phenomena and view the Earth as a complex system.
One could imagine a planet that did not rotate, in which case the air currents inside hurricanes would move in a straight line. However, the reality is different, as the Earth rotates, leaving its mark on the movement of the atmosphere.
The Earth's rotation creates an important phenomenon called the Coriolis effect: this phenomenon affects moving objects, including the air currents inside hurricanes.
Under the influence of the Coriolis effect, the updrafts and downdrafts within a hurricane begin to shift laterally: it is this process that gives hurricanes their characteristic spiral shape and determines the direction of rotation.
The direction of rotation of hurricanes depends on their geographical location: in the Northern Hemisphere, hurricanes rotate counterclockwise, and in the Southern Hemisphere, clockwise. This is due to the interaction of the rotating Earth and air currents.
What happens if two hurricanes collide in the same area? This does not result in one hurricane absorbing the other—instead, a strange phenomenon known as the Fujiwara effect occurs. The hurricanes will circle around each other, maintaining their individuality, and the result of this “dance” is complex movements of clouds and winds.
As for the possibility of a hurricane crossing the equator, this proves to be extremely difficult due to a combination of factors:
The weakness or absence of the Coriolis effect at the equator, which is necessary to maintain the rotation of a hurricane.
The energetic disadvantage of changing the direction of rotation when crossing the equator, which requires significant changes in the storm structure.
Vertical winds and other atmospheric conditions near the equator that may be unfavorable for supporting a hurricane.
As a result, hurricanes do not usually form directly near the equator, but rather form at a greater distance—approximately 5–10 degrees latitude (550–1,100 km) and beyond. Although the minimum distance can be about 300 km, the further from the equator, the stronger the Coriolis effect and the more favorable the conditions for hurricane formation.
Thus, despite the thermal potential of tropical waters, the physical processes occurring at and near the equator create a complex barrier to the passage of tropical hurricanes through this region. This interesting phenomenon continues to capture the attention of scientists, contributing to the understanding of the complex relationships in the Earth's atmosphere.
Джерело: Source
