How do hurricanes form and why is their east side worst?

Hurricane Ian made landfall on Wednesday as a Category 4 storm, tearing through southern parts of Florida and threatening to move up through Texas and South Carolina. It is thought to be one of the strongest storms to ever reach mainland United States and the infrastructure damage and deadly floodwater will provide severe problems for residents long after the storm has passed.

Experts had warned of an above-average hurricane season this year and in recent weeks researchers had identified a significant tropical storm forming in Atlantic. Hurricanes typically begin life in the sea near to the equator, where the waters are warmest.

The warm sea heats the air and as water evaporates it rises and cools, condensing into large water droplets. This forms large cumulonimbus clouds which release more heat into the air, and cause more water to evaporate and continue the cycle, building the cloud columns higher and wider.

As the column grows taller it becomes very unstable as the air pressure increases, sparking strong winds to surge out from the central point. This is called a tropical depression and it is at this point that the column of clouds begins to move in a circular motion, spinning faster and faster.

Once the wind speeds reach 39mph the tropical depression becomes a tropical storm, the phenomenon identified in the Atlantic weeks ago. As the process continues the winds blow stronger and begin to push the spinning column of cloud either east or west.

The winds gain momentum as the column moves and once the wind speed reaches 74mph the storm officially becomes a hurricane. By this point the system is at least 50,000 feet high and 125 miles wide, with the eye of the storm spanning up to 30 miles alone.

Is the ‘right’ side of the hurricane more dangerous?

You may have heard meteorologists refer to the ‘dirty side’ of a hurricane, or suggest that the eastern side is more deadly. This is a real phenomenon and one that has to do with steering currents driven by atmospheric air flow.

In the northern hemisphere the winds that cause the system to spin are usually strongest in the upper-right quadrant, when seen from an aerial view. This means that the energised ‘right’ side of the hurricane can create higher wind speeds, larger waves and a more pronounced storm surge.

This effect is even more dangerous if the right side of a hurricane aligns with a body of water, such as a bay or a river. This is very difficult to predict precisely, so officials normally advise residents stay away from all bodies of water when issuing a hurricane warning.