Tornadoes And Microbursts

The wind damage from a hurricane results mainly from the prolonged, violent "blow" in the eyewall. Few hurricanes retain deadly wind speeds farther than about 160 km (100 mi) inland, although this depends to a large extent on the terrain, and considerable damage can still result from sustained winds of 50 to 60 kt (about 60 to 70 mi/h). Hurricanes can produce tornadoes, however, and these have higher wind speeds than those in the general circulation of the eyewall.

Tornadoes are most frequently observed in the forward semicircle of a hurricane, especially in the right front quadrant. But they can take place anywhere in the rainbands or eyewall the storm. In a hurricane, a tornado may move much faster than a typical "Texas twister," and can strike with little or no warning. The tornadoes associated with a tropical hurricane are, however, rarely as large or violent as their continental counterparts. Hurricane-spawned tornadoes can nevertheless tear the roofs off of buildings, shatter windows, overturn automobiles, strip trees, and cause other serious damage to property. As the hurricane moves into the temperate latitudes, the tornadoes may become more violent. Hurricane Camille, in August, 1969, caused significant tornado damage throughout the Gulf Coast and southeastern United States as she moved northeastward past the 30th parallel.

Microbursts can also occur in hurricanes, especially in the eyewall where the most intense thunderstorm activity is found. These are the same phenomena sometimes seen in strong thunderstorms associated with frontal cyclones in the temperate latitudes. As the air descends and strikes the surface, it "spills out" in all directions like a water stream striking a hard floor, momentarily adding to the wind speed in some directions, momentarily reducing it in other directions, and momentarily shifting its direction in some places.

An exceptionally strong wind gust or lull in the eyewall of a hurricane, particularly if it is attended by a perceived change in the air pressure (felt on the eardrums), can signify a passing tornado or microburst. The author noticed several instances of this phenomenon during the passage of the forward portion of the eyewall of Hurricane Andrew in Homestead, Florida. The wind would suddenly abate for a couple of seconds, and high pressure was felt on the eardrums. After the storm, some trees were blown down at angles much different from what would have been expected if the winds had blown in straight lines at all times. This lends support to the hypothesis that the eyewall of Andrew contained tornadoes or microbursts, or both.

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  • jens
    Can microbursts occur in hurricanes?
    7 years ago

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