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TRAPPED
Cars semi-submerged on Prospecton Road, south of Durban, on Tuesday Image
credit: Thuli Dlamini
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At least eight people
have died in South Africa after a devastating storm hit the country.
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A
container ship came away from its mooring during storm and blocked Durban port
Reuters
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The
SA Weather Service described it as a "super-cell thunderstorm", which
South Africa’s Times paper says is characterised by a deep rotating up-draft
like a tornado, large hailstones, strong winds.
According
to the Business Day paper, winds of 70km/h (90km/h) pummelled KwaZulu-Natal
province on Tuesday.
An
eight-year-old was among those who died in the north of the province, a
provincial official told the IOL news site.
"In
ward eight, Mbewunye, an eight-year-old girl was struck by lightning and in
ward two, KwaMngxangala area, a 46-year-old male drowned while trying to cross
a river,” Lennox Mabaso said.
How Supercell
Storms Produce Devastating Tornadoes
Supercell
thunderstorms have been responsible for major tornadoes that have demolished
parts of the United States (this happened in South Africa as well) since modern day record keeping started in 1950.
Supercells
are different from normal thunderstorms because they are much more organized
and often have a strong circulation, which not only feeds the storm a mixture
of moisture, dry air, warm air and cold air, but also aids in funnel cloud
formation. The cloud base of the supercell typically has three sections. One
area where there is no precipitation, the precipitation area and the
lower-hanging wall cloud. Funnel clouds form where this rotating wall cloud
lowers from the overall base of the storm. A tornado is born where the funnel
touches the ground. An anvil cloud is often visible in supercell thunderstorms.
This cloud is very high in the atmosphere and is made up of ice crystals. In
the strongest supercell thunderstorms, part of the cumulonimbus cloud pokes
above the anvil.
AccuWeather.com
Expert Senior Meteorologist Henry Margusity said that tornadoes that are
produced by supercell thunderstorms develop in cycles.
"The
tornadoes develop, mature and dissipate," he said.
The
cycling process includes tornadoes touching down, traveling distances and
picking back up, Margusity said. When the tornado touches down and travels for
a while, this can be thought of as the tornado maturing. When the tornado
retracts into the sky, the storm dissipates.
When
the tornadoes lift and go back down to the ground it produces multiple
tornadoes. It is not just one isolated tornado.
"It
is like a family of tornadoes," Margusity said.
The
tornado that touched down in Moore, Okla., was rated an EF5 with a base larger
than 1 mile and a destruction path of 17 miles. This tornado was caused by a
supercell thunderstorm. The average warning time, from the time the warning is
issued to when the tornado strikes, is 13 minutes. Community members were given
16 minutes from the time the warning was issued until the time the tornado
ripped through Moore.
A
similar tornado touched down in Woodward, Okla., April 14, 2012. An EF3 tornado
that was on the ground for 37 minutes caused massive destruction and loss of
life. The NWS issued a tornado warning at midnight and by 12:33 a.m., there
were reports that a tornado had touched down.
The
people of Joplin, Mo., were victims of a destructive tornado caused by a
supercell thunderstorm on May 22, 2011. An EF5 tornado that was three-fourths of
a mile ripped through the city, resulting in 158 deaths and more than 1,000
people injured. The Joplin tornado was ranked seventh in U.S. history of most
deadly tornadoes and the single deadliest tornado since modern record keeping
began in 1950, according to the NWS.
Another
tornado spawned by a supercell, killed 116 in Flint, Mich., on June 8, 1953.
This tornado was originally the single deadliest tornado. This EF5 tornado had
a destruction path of 27 miles and moved at 35 mph.
After
a warning has been issued, it is important to seek shelter immediately. With an
EF3, 4 or 5 tornado, the only safe place to be is underground, according to
AccuWeather.com Expert Senior Meteorologist Dan Kottlowski.
A
safe room described by the Federal Emergency Management Agency (FEMA) is,
"a hardened structure specifically designed to meet the FEMA criteria and
provide 'near-absolute protection' in extreme weather events, including
tornadoes and hurricanes," according to www.fema.gov.
However, Kottlowski said that the safe room must be reinforced with rebar and concrete. The shape of the room and the area in which it is built may also be an important role in staying safe in a tornado. Shaping the room like a dome or igloo and being mindful of which way the wind blows toward your house are two suggestions that Kottlowski makes.
Source: https://www.accuweather.com/
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