Tracking tropical cyclone Ava's movements IMAGE: Supplied
The South African Weather Service (SAWS) has issued a cyclone alert as the first tropical cyclone of the season, called Ava, is sitting off the northeastern tip of Madagascar, Zululand Observer reports.
While Ava is unlikely to affect our region, it will dominate the weather in the south-western Indian Ocean over the coming days, and expected to affect parts of the Mozambican Channel early next week.
READ MORE: WATCH: Cyclone Enawo batters Madagascar
The system is expected to make landfall over Madagascar tomorrow (Friday), bringing with it forecast wind speeds of up to 150km/h.
SAWS is continually monitoring the development of the system and will advise accordingly.
According to cyclocane.com’s cyclone tracking feature, Ava is expected to increase in intensity from her current 50 knots (92km/h) to 55 knots (102km/h) this evening and 65 knots (120km/h) tomorrow morning.
Once Ava makes landfall, her speed is forecast to decrease to 50 knots (92km/h) by tomorrow evening, thereafter decreasing more during the course of the weekend and early next week.
‘Newly formed tropical cyclone Ava is expected to bring life-threatening impacts to Madagascar into this weekend,’ said Accuweather Meteorologist, Eric Leister.
‘Ava is the first tropical cyclone of the season in the south-western Indian Ocean, with winds equal to a tropical storm in the Atlantic and eastern Pacific oceans.
‘Ava is expected to strengthen as it approaches the east coast of Madagascar into Friday.’
Intensity classifications
Cyclones are classified according to their sustained wind speed.
• Tropical depression: a tropical disturbance that has a clearly defined surface circulation with maximum sustained winds of less than 63km/h.
• Tropical storm: sustained winds between 63km/h and 119km/h. At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present.
• Tropical cyclone: sustained winds of 120 to 157km/h. A cyclone of this intensity tends to develop an eye, an area of relative calm (and lowest atmospheric pressure) at the centre of circulation. The eye is often visible in satellite images as a small, circular, cloud-free spot. Surrounding the eye is the eye wall, an area about 16 to 80 kilometres wide in which the strongest thunderstorms and winds circulate around the storm’s centre.
• Intense tropical cyclone: Winds between 158 and 209km/h.
• Very intense tropical cyclone: Winds from 210km/h and higher.
Interesting information
Maximum sustained winds in the strongest tropical cyclones have been estimated at about 340 km/h – equal to the top speeds of a Formula One racing car.
Although a cyclone’s winds can be incredibly destructive, these systems also cause severe rainfall.
Cyclone Domoina (which hit our coastline in late January 1984), was only classified as a severe tropical storm, and yet dropped about 950mm in causing 100 year floods in KZN and record rainfall in Swaziland. There were more than 200 deaths caused by this storm.
The south-western Indian Ocean cyclone season officially lasts from 15 November to 30 April. The 2016/17 season was a particularly quiet one, with only five tropical systems developing to ‘tropical storm’ status, which Ava currently is.
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