INTRODUCTION
A visit by a powerful lady, Cyclone Dando
An extratropical disturbance formed east of Madagascar on January 11, and transitioned into a subtropical depression the next day. It retained subtropical characteristics as it moved towards the African mainland, but by January 15 it reached the equivalent of cyclone strength and was allocated the name Dando.
On January 16 the last advisory was issued for Dando as the system weakened to a remnant low. After making landfall on January 17, the remnants of Dando dissipated inland on January 18.
A tropical cyclone is a storm system characterized by a low-pressure centre and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapour contained in the moist air.
The characteristic that seperates tropical cyclones from other cyclonic systems is that at any height in the atmosphere, the center of a tropical cyclone will be warmer than its surroundings; a phenomenon called “warm core”.
The eye, eyewall and surrounding rainbands that are characteristics of tropical cyclones are clearly visible from space.
The term “cyclone” refers to such storms’ cyclonic nature, with counterclockwise wind flow in the Northern Hemisphere and clockwise wind flow in the Southern Hemisphere.
Many tropical cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere are favourable. The background environment is modulated by climatological cycles and patterns such as the Madden-Julian oscillation, El Niño-Southern Oscillation, and the Atlantic multidecadal oscillation.
It is interesting to learn that it was only upon dissipation of cyclone Dando that the real damage began. Hoedspruit was the hardest hit area. It is known that Cyclones can cause rainfall & flooding 40km inland from where the cyclone heads over land.
In the case of Hoedspruit though, it is 230km from the nearest point of Mozambique coastline. This area around Hoedspruit experienced 450mm of rainfall in a 30 hour period. The highest record of rainfall was at the foot of Mariepskop where 500mm of rain fell in the same time. The rainfall for many areas was equal to the annual rainfall. It would appear that pressure systems around the escarpment acted as the barrier for further westward movement & thus the intense rainfall around the Mariepskop & Hoedspruit area.
The two major rivers that flow out of the escarpment, the Olifants & the Bylde, both broke their banks. There have been 9 cyclones in the region so far this cyclone season (starting in December 2011) with the most recent being cyclone Irina which has just dissipated further south east.
ROGERS BIRD FACT
BATELEUR EAGLE
Terathopius Ecaudatus
Area:
Found throughout Africa, south of the Sahara.
Family:
Part of the Eagle Family
Interesting Facts:
Females are 30% larger than Males. When the youngest first hatches the tail is substantially longer than the feet.
This allows for the bird to learn how to fly. In the subsequent 4 moults to adulthood, the tail gets progressively shorter so that by the time it is old enough to fend for it’s territory and raise offspring it’s centre of gravity is moved way forward. This allows for low level flight in search of food and thereby allowing it to compete with much larger vulture species.
Bateleurs are highly opportunistic feeders. They take carrion from small and large carcasses and pirate prey from other raptors or stork.