Factors Which Can Weaken Hurricanes

As mentioned earlier in this course, tropical cyclones or hurricanes prefer warm, moist environments with low vertical wind shear. Therefore, it follows that the opposite of these factors would cause hurricanes to weaken. If a hurricane moves over an area with relatively cool sea surface temperatures, it will generally weaken in intensity. Likewise, it will also weaken in intensity if it moves into a drier environment or an environment with strong vertical wind shear. Strong high or low pressure systems, which disrupt the flow around a tropical cyclone, can also weaken the storm by preventing the warm sea surface temperatures from heating up the air just above the surface of the ocean.

The most obvious condition which will weaken a hurricane is making landfall. This is due mostly to losing the energy from the sea surface temperatures, but also from the increased friction with the rough ground causing windspeeds to diminish. Sometimes, hurricanes can persist, or even restrengthen slightly, over land if there is enough warm water available for it to use as an energy source.

Once the flow around a hurricane is no longer a closed circulation, then the storm loses its tropical characteristics and hurricane forecasters will stop issuing advisories for it. This disruption to the circulation is usually caused by either making landfall or the higher wind shear in the mid-latitudes as the tropical cyclone drifts poleward.

Because hurricanes feed on warm, moist environments, the intrusion of cooler and drier air can also cause tropical cyclones to weaken. Drier air can often be observed in water vapor imagery as pockets of yellow or red pixels.