Why do hurricanes lose strength over land? This article will learn about the factors that cause hurricanes to weaken and even die as they travel overland.
Hurricanes are born out of certain weather conditions, and these weather conditions are what keep hurricanes alive as they travel across the ocean.
Many factors are known to contribute to the weakening of a hurricane when it reaches land, including its proximity to cooler temperatures and lower air pressure and the friction caused by winds moving through the atmosphere.
Formation of a Hurricane
Hurricanes develop over regions of low pressure over large bodies of water.
When warm surface air rises, it cools and becomes heavier, causing it to fall until rain or snow falls, which adds moisture to the area.
As more warm air is forced up from below, more vapor is added until a hurricane forms. A hurricane often begins with a tropical wave.
The Caribbean and Gulf of Mexico are ideal locations for hurricanes because they have warm water, at least 26.5 degrees Celsius over a depth of 50 meters.
A pre-existing weather disturbance that becomes a tropical wave is responsible for thunderstorm activity that can turn ocean heat into hurricane fuel.
The Strength of Hurricanes, Equator and the Tropics
The strength of hurricanes and other tropical storm systems is dependent on the warm, tropical ocean waters where they form.
Warm water collects and stores heat near the equator as the season progresses.
Suppose the maximum sustained winds of a tropical cyclone reach 74 miles per hour (mph) or more at 10 meters above the surface.
In that case, it is considered a hurricane in the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and eastern North Pacific Ocean.
If a tropical cyclone’s maximum sustained winds reach at least 157 mph, it is classified as a “major” hurricane.
Fact: Hurricanes form within five degrees latitude of the equator, the band of land between the Tropic of Cancer and the Tropic of Capricorn.
Cold Water and Hurricane Strength
Because hurricanes need warm water to maintain their strength, their destructive power will weaken when they move over water-cooled by cold air or land.
Ocean surface temperatures also influence hurricane intensity – the warmer the water, the more powerful the storm.
Evaporation and Hurricane Formation
A hurricane forms when warm seawater evaporates and gathers in the atmosphere. The water vapor powers the storm and carries it forward while it pulls more warm seawater yet up to force it further.
As a storm moves over land or cold ocean water, it loses energy and eventually dissipates.
A recent study showed a link between ocean surface temperatures and tropical storm intensity.
That study found that higher ocean temperatures fuel more energetic storms.
They also lose contact with their energy source (the ocean’s warm water), and they tend to weaken and break apart.
If you were wondering why do hurricanes lose strength over land or cold water, this is your answer.
Reasons Why Hurricanes Lose Strength Over Land
In this section, we’ll delve into the specific factors as to why do hurricanes lose strength over land.
1. Landfall
The heat source most needed by a hurricane is warm water. (Here, a period is used because the sentence only describes one feature of hurricanes.)
Once a hurricane makes landfall, it loses contact with the ocean and its heat source and, therefore, dies or rapidly loses strength.
2. Aerosol Particles
Over the land, air masses tend to be drier and have more aerosols than over the ocean; therefore, less moisture is carried into storms and reduced cloud coverage.
Such cooling facilitates the air pressure, and thus the air sinks; this disruption of clouds enables hurricanes to weaken.
3. Friction with Land
One of the main reasons hurricanes are weakened when they hit land is their friction.
This happens because friction heats the surface, creating less difference in temperature between the ocean and the air.
The winds die down, less water evaporates, and there's less energy to feed the storm.
4. Vertical Wind Shear
Often, as a hurricane moves around on land, its winds change direction or speed at different altitudes.
This change in wind direction or speed usually makes the storm less threatening because of mixing.
Mixing brings warm, dry air into the storm’s eyewall, the middle circle of clouds surrounding the eye.
When this happens, the storm’s eyewall loses its strength and pushes weaker air away from its center. This weakening produces less rainfall.
Upper-level solid winds typically found above hurricanes create high levels of wind shear, the change in wind direction, or speed with height.
Wind shear keeps storms from intensifying by separating cloud tops from their bases.
The vertical circulation around the eyewall becomes tilted, forcing heat and moisture away from the low-level circulation of the storm.
As a result, development gets more complicated, and progress is slowed.
Extratropical Cyclones
Extratropical cyclones, also known as nor’easters, are created when tropical hurricanes move into the mid-latitudes.
These types of cyclones require fronts to form over land, and they normally occur much farther north than hurricanes do.
Unlike hurricanes, extratropical cyclones form when high and low pressure areas collide, causing a storm system to form.
In most cases, extratropical cyclones don’t become active until a few days after the hurricane that caused their development has dissipated.
Not all extratropical cyclones are created equal; some are relatively weak and produce only light rain or snow, while others result in blizzards, severe flooding or damaging winds.
Fact: One of the most powerful extratropical cyclones to hit New England was The Perfect Storm of 1991.
Damages Caused by Hurricanes Over Land
Hurricanes and other tropical storms dump torrential rains that often cause rivers to flood their banks or mudslides to form.
An estimated 10,000 people die each year due to hurricanes and tropical storms.
These dangerous weather systems are characterized by strong winds, waves, and even tornadoes; however, the millions of gallons of water make these systems so difficult.
Just as it’s essential to understand why do hurricanes lose strength when they move over land, it’s also essential to understand the damages they cause before they die down.
Here are some of the havoc caused by hurricanes on land:
Strong Winds
When winds reach speeds between 39 and 73 miles per hour, they are considered moderate breezes.
Moderate breezes can be refreshing, especially on hot summer days. Winds with hurricane force, however, can damage buildings and uproot trees.
Storm Surges
Hurricanes are destructive storms that are known for their fierce winds and rain and their ability to cause coastal flooding.
Storm surges are the deadliest results of hurricanes and can cause water damage to structures near the coast.
In the United States, hurricanes that affect the Atlantic or Gulf Coast tend to impact coastal regions significantly.
Rising sea levels can pummel coastal areas, engulfing any object in a storm surge’s path.
Note: The most devastating result of hurricanes is storms surges, which can cause sea levels to rise rapidly as a hurricane makes landfall.
Flooding
Heavy rainfall is often associated with hurricanes and can lead to significant flooding. The worst of the flooding happened in 2017 with Hurricanes Harvey and Irma.
The first storm dropped 50 inches of rain on parts of Texas and Louisiana, while the second storm produced 30 inches of rain in Florida.
Tornadoes
During category three hurricanes, winds can reach upwards of 156 miles per hour; this causes multiple tornadoes, uprooting trees and homes, and increasing the amount of windborne debris.
Read Next: Can a Hurricane Cause a Tsunami?
Final Thought
Storms like hurricanes generally lose force once they move onshore and overland. While winds and rainfall appear to increase at a certain distance inland from the coast.
This is an illusion created by the differences in the way water drains over land compared with how it drains over water.
Winds, for example, lessen because of friction created over land compared with the friction created over water. This explains why do hurricanes lose strength over land.
However, because the storm’s rain is being wrung out as it passes, it appears to be dumping more rain farther away from the coast than closer to it, when in fact, its overall rate of rainfall has slowed.
