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NSF PR 95-58 - September 7, 1995
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Cheryl Dybas |
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Hurricanes Past, Present, and Future: New Perspectives
This year is setting a record pace in tropical storm
formation across the Atlantic Ocean. Below are updates
on two new areas of hurricane research being pursued
by scientists at the National Center for Atmospheric
Research (NCAR) in Boulder, Colorado, funded by the
National Science Foundation.
"Hypercanes": A Possible Mechanism for Species Extinction?
Could a series of colossal hurricanes have led to
the mass extinction of dinosaurs and other species?
A computer model created by NCAR scientist Richard
Rotunno and colleagues indicates that possibility.
Rotunno, Kerry Emanuel of the Massachusetts Institute
of Technology, and three other scientists argue that
"hypercanes" - theoretical superstrong hurricanes
-may have been a crucial agent in past extinctions.
During the Late Permian period, about 245 million
years ago, some 96 percent of all species disappeared.
A later event extinguished 75 percent of all species.
Giant meteors or volcanic eruptions have been cited
as possible causes. The authors contend that neither
type of event could inject enough long-lasting debris
into the stratosphere to affect global climate on
the scale needed for mass extinction. However, meteors
or undersea eruptions might have been able to heat
swaths of ocean a few tens of kilometers wide to temperatures
as high as 50 degrees C (122 degrees F).
Rotunno took a hurricane model he created with Emanuel
and tested it under these conditions. The superheated
patches of ocean in the computer model quickly generated
tropical cyclones with central pressures as low as
200 millibars and wind speeds as high as 300 meters
per second (675 miles per hour, approaching the speed
of sound). After about two days, the storms settled
into a steady state with winds still around 340 mph.
Such storms could produce vast sheets of stratospheric
clouds that would alter radiation patterns and perhaps
trigger ozone depletion, the scientists contend. Was
Hurricane Andrew a Prelude to Future Coastal Disasters?
Hurricane Andrew raked south Florida in August 1992,
causing some 40 deaths and $30 billion in damage.
Yet it could easily have been worse. Had Andrew struck
the Florida coast only 20 miles farther north, the
damage could have been as much as $75 billion, according
to several analyses. Had it struck areas along the
East Coast or Gulf Coast where evacuation plans are
inadequate, many more people could have died. These
are among the messages contained in Hurricane Andrew
in South Florida: Mesoscale Weather and Societal Responses.
The report was recently done by Roger Pielke, a visiting
political scientist at NCAR. Pielke provides an overview
of the human factors that interacted with the physical
reality of Andrew to create the disaster that occurred.
The report is the first in a series in which Pielke
examines several weather disasters, including the
eastern U.S. "superstorm" of March 1993, and the Midwest
flooding of that summer, from both scientific and
societal viewpoints. Although improved warnings since
the 1950s have reduced the death toll from U.S. hurricanes,
damage costs continue to rise. Andrew struck an area
(Dade County) with the country's most stringent hurricane
building codes, yet the resulting damage made it clear
that the codes were not being fully enforced, says
Pielke. In fact, homes built since 1980 suffered more
damage than did older homes. "Even with strict enforcement,
Andrew still would have been the costliest hurricane
in history. Thus, it is indeed frightening to consider
the potential impacts of an Andrew like storm on other
coastal communities." Despite improvements in warnings,
large losses of life could still occur from a U.S.
hurricane, according to Pielke. The evacuation of
700,000 people for Andrew was judged a success. However,
the memory of that storm may result in more residents
than necessary evacuating ahead of the next storm.
Ironically, this could impede the flight of those
most in danger. Due to a "post-Andrew effect," evacuation
times in the Florida Keys might increase from 37 hours
to as much as 80 hours for a major hurricane.
According to Pielke, the busy 1995 hurricane season
is a "window of opportunity" for coastal communities
to examine their vulnerability to severe weather.
"The important questions are: How vulnerable are we?
What decision processes are in place in regard to
hurricanes? How can we use wisdom gained from 500
years of hurricane experience in North America, instead
of ignoring or forgetting it?" In his report, Pielke
includes a checklist that includes more than 176 important
decisions each community vulnerable to hurricanes
should make. "In some coastal areas, especially low-income
ones," Pielke warns, "the evacuation plans are outdated."
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