Scientific Report | Tropical cyclones take a rare path and merge with polar air masses in the North Atlantic

Arab Weather - Weather experts at the Arab Weather Regional Center are following up on the latest numerical computer modeling outputs indicating the behavior of weather systems in the region, specifically the North Atlantic Ocean, which appears striking, as tropical weather systems meet with polar ones, producing patterns of severe weather disturbances, especially in Western Europe.

Growing La Nina phenomenon boosts tropical cyclone activity over Atlantic Ocean

In detail, the world is witnessing the growth of the La Nina phenomenon, which represents the cooling of the tropical part of the Pacific Ocean. Studies have shown that the La Nina phenomenon directly affects the activity of tropical cyclones in the Atlantic Ocean, because La Nina tends to reduce the wind shear force in the tropics. At the same time, the abundant heat in the tropical Atlantic Ocean and the Caribbean Sea creates more energy to fuel the development of tropical storms in their active season that begins on June 1 and continues until November 30. The tropical region of the Atlantic Ocean is recording warmer than usual temperatures, which enhances the development of tropical cyclones, one of which is now active over the Atlantic Ocean.

Rare behavior of tropical cyclones towards the northeast

Looking at the behavior of hurricanes, or hurricane propagation, we find that they are directed by global winds. The prevailing winds surrounding a hurricane, also known as the environmental wind field, guide the hurricane along its path. The hurricane propagates in the direction of this wind field, which also affects the speed at which the system propagates. While each storm follows its own path, the motion of each hurricane is influenced by a variety of surrounding factors.

A low pressure system is affecting the central Mediterranean and moving eastward in the coming days. What is its effect on the Levant?

Atlantic hurricanes typically move westward toward the coasts of the Americas, and the Beta Effect controls the path of hurricanes, an effect related to the change in the Coriolis force with latitude. This effect occurs in the atmosphere or oceans as the Earth's rotation speed changes with latitude, causing the path of air masses or water currents to deviate. This effect is particularly important in understanding how tropical cyclones move, as the change in the Coriolis force causes hurricanes to deviate north or south (depending on the hemisphere) over time, and the deviation increases the further the storm moves from the equator, in addition to the effects of the Gulf Stream, a warm water current in the North Atlantic Ocean, which provides additional energy to hurricanes and pulls them north and east toward the coasts of the United States or Europe.

Tropical cyclones take a rare path and merge with polar winds, which changes their characteristics from tropical to baroclinic.

According to computer modelling, Atlantic hurricanes are expected to behave in a rare way, shifting northeastwards as weather conditions change. As hurricanes move northwards, they lose their tropical strength due to the colder northern waters, as well as their interaction with and merging with polar air masses coming from the north. Tropical cyclones become extratropical storms, taking on baroclinic characteristics, and becoming frontal weather systems that continue to move towards the European coasts. Although these storms are weaker than their parent (strong tropical cyclones), they can cause severe weather conditions such as heavy rains and strong winds in areas such as Britain, Ireland, Portugal, and even parts of Spain and France in the coming period.

Jordan | Monthly weather bulletin for October 2024

God knows best.