WHY HURRICANES RARELY STRIKE COSTA RICA

In meteorology, a tropical cyclone, disturbance, depression, or storm, typhoon, or hurricane, depending on strength and location are types of low pressure systems which generally form in the tropics.

Hurricane is the term used to describe tropical cyclones that form near Central America, and they need the warm humid air above tropical seas in order to develop.

Furthermore, they form only during the summer and early fall, when the tropical seas are about 80 degrees Fahrenheit or warmer. But you won’t normally see hurricanes form right at the equator. That’s because at zero degrees latitude there isn’t enough turning of winds in the atmosphere to give tropical cyclones the “spin” they need to get started.

This turning of the winds is known as the Coriolis Force or Effect.

Nearly all hurricanes form within 30 degrees of the equator and 87% form within 20 degrees. However, because the Coriolis effect initiates and maintains tropical hurricane rotation, such hurricanes rarely strike land less than 10 degrees from the equator. The Coriolis Effect initiates and helps maintain the rotation of a tropical hurricane. This rotational force is zero at the equator and increases as you travel away from the equator. Once a tropical storm is formed, wind determines its movement and there is very little cross-equatorial flow of wind, as the main winds steer the storm away from the equator.

Also, hurricanes that form in the Caribbean are not likely to turn toward Costa Rica.  Because Caribbean tropical storms normally are pushed northwest, along with the steering currents of trade winds from the east, then a clockwise flow of high pressure to the north. This has a tendency to turn them northward away from Costa Rica. 

Costa Rica is located between 8 and 12 degrees north of the equator, below the path of most hurricanes.

There are seven tropical cyclone zones “basins” where storms occur on a regular basis and Costa Rica is not located in the affected areas.

Here are some terms and definitions that relate to hurricanes.

Coriolis Force: An artifact of the earth’s rotation. Once air has been set in motion by the pressure gradient force, it undergoes an apparent deflection from its path. This apparent deflection is called the “Coriolis force” and is a result of the earth’s rotation. The Coriolis effect initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds. That force is the heat of condensation.

In the northern hemisphere, the earth’s rotation is deflected to the right by the Coriolis force. The amount of deflection the air makes is directly related to both the speed at which the air is moving and its latitude. Therefore, slowly blowing winds will be deflected only a small amount, while stronger winds will be deflected more

Pressure Gradient Force: Directed from high to low pressure. The change in pressure measured across a given distance is called a “pressure gradient”. The pressure gradient results in a net force that is directed from high to low pressure and this force is called the “pressure gradient force”.

Geostrophic Wind: Winds balanced by the Coriolis and Pressure Gradient forces. An air parcel initially at rest will move from high pressure to low pressure because of the pressure gradient force (PGF). However, as that air parcel begins to move, it is deflected by the Coriolis force to the right in the northern hemisphere (to the left on the southern hemisphere). As the wind gains speed, the deflection increases until the Coriolis force equals the pressure gradient force. At this point, the wind will be blowing parallel to the isobars. When this happens, the wind is referred to as geostrophic.

The writer, Tom Rosenberger has lived and worked in Costa Rica for 23 years and from his travels throughout the country inspecting property and construction he has acquired a wealth of knowledge about living and doing business here. Tom has other blogs you may like: CostaRicaBusiness, and CostaRicaConstructionSpecialist. You can send Tom an email at; tom@CostaRicaHomeBuilder.com.