Hurricanes: Their Nature and Impacts on Society - Climate Science ...

HURRICANE IMPACTS
125
to 135 mph over the ocean <strong>and</strong> 165 mph over a forest. A wind of 100 mph
over a forest at 36 feet, however, is harder to sustain than over the ocean at
the same height, as a direct result of the greater gustiness over the forest. This
larger turbulence acts to decelerate the wind as wind energy' is transferred to
the forest..
5.2.4 Rainfall
Rainfall is often excessive at <strong>and</strong> after a tropical cyclone makes l<strong>and</strong>fall,
particularly if the very moist air of the storm is forced up <strong>and</strong> over mountains.
These storms are particularly efficient rain producers when compared with
other tropical <strong>and</strong> summer precipitation systems (Lawrence <strong>and</strong> Gedzelroan
1996).
Rainfall from hurricanes is beneficial to agriculture, such as the rains from
Hurricane Dolly (1995) in southern Texas <strong>and</strong> northeastern Mexico which
relieved a drought (Rippey 1997, cf. Sugg 1967). Figure 5.5 illustrates observed
rainfall associated with an August Atlantic tropical cyclone of 1928 as it moved
up the Atlantic coast east of the Appalachians. Even relatively weak tropicallike
disturbances can result in extreme rainfall, as seen, for example, over coastal
Texas in September 1979 in which upwards of 19 inches (483 millimeters) of rain
inundated the area over a period of several days (Bosart 1984). Occasionally, for
reasons not completely understood, rainfall is light in the vicinity of hurricanes.
Hurricane Inez in 1966, for instance, resulted in only a few drops of rain in
Miami for several hours when the center was south <strong>and</strong> south-southwest of
Miami <strong>and</strong> at its closest point to the city. At the time, Miami was under the wall
cloud <strong>and</strong>, normally, torrential rains would have been expected. As a result of
the absence of rain, the strong winds blew salt spray many miles inl<strong>and</strong>, causing
severe damage to vegetation from salt accumulation. Homestead Air Force
Base, south of Miami <strong>and</strong> closer to the hurricane center, received only 0.62
inches (15.7 millimeters) of rain during the entire storm.
5.2.5 Tornadoes
Tornadoes are also a threat from tropical cyclones. Much of the damage of
Andrew was associated with tornadic vortices whose wind speeds were added
onto the large-scale hurricane winds (Black <strong>and</strong> Wakimoto 1994). These
rapidly rotating small-scale vortices are spawned in squalls, usually in the front
right quadrant of the storm with respect to the storm's track. While these
tornadoes are not often as severe as the major tornadoes that are associated
with springtime Great Plains thunderstorms, loss of life <strong>and</strong> property damage
* Powell, Houston <strong>and</strong> Reinhold (1996; Figure 4 of their paper) provide a framework to obtain
st<strong>and</strong>ardized hurricane wind observations over l<strong>and</strong> <strong>and</strong> over the ocean.