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Sunday October 07, 2007 |
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 Week No.41 Fact No.18 |
Some differences
between tropical cyclones
and tornadoes:
While both tropical cyclones and tornadoes are atmospheric
vortices, they have little in common.
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Tornadoes have
diameters on the scale of 100s of meters and are
produced from a single convective storm (i.e.
a thunderstorm or cumulonimbus).
Tropical cyclones have
diameter on the scale of 100s of *kilometers* and is
comprised of several to dozens of convective storms.
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Tornadoes are
produced in regions of large temperature gradient, while
tropical cyclones
are generated in
regions of near zero horizontal temperature gradient.
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Tornadoes are primarily an over-land
phenomena as solar heating of the land surface usually
contributes toward the development of the thunderstorm
that spawns the vortex (though over-water tornadoes have
occurred). In contrast,
tropical cyclones are purely an oceanic
phenomena - they die out over-land due to a loss of a
moisture source.
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Tornadoes
typically last on the scale of minutes, while
Tropical cyclones
have a lifetime that is measured in days.
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Posted by Joan Mc Donald |
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Monday September 17, 2007 |
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Week No.38 Fact No.17 |
The
largest number of hurricanes in the Atlantic Ocean at
the same time?
Four hurricanes
occurred simultaneously on two occasions. The first
occasion was
August
22, 1893, and one of these eventually
killed 1,000- 2,000 people in Georgia
South Carolina.
The
second occurrence was September 25,
1998, when Georges, Ivan, Jeanne and
Karl persisted into September 27, 1998
as hurricanes. Georges ended up taking
the lives of thousands in Haiti.
In 1971
from September 10 to 12, there were five
tropical cyclones at the same time;
however, while most of these ultimately
achieved hurricane intensity, there were
never more than two hurricanes at any
one time.
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Posted by Joan Mc Donald |
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