Fickle tropical storm Dineo to bring heavy rainfall

HEAVY rain is expected in South Africa tomorrow night (Thursday, 16 February), as Dineo makes land.

“In the last few hours, Dineo’s track has become more westerly, with recent movement being towards the west-south-west at 7 knots (about 14km/hr).

Dineo is really living up to the notoriously fickle and unpredictable nature of such tropical systems. Overnight, Dineo’s track began shifting to adopt a more westerly trajectory, departing from the mostly south-westerly track which dominated its movement yesterday. The new track will take the system on to the coast early this evening, near Msinga, somewhat north of Inhambane,” said South African Weather Service’s chief forecaster, Kevin Rae.

The projected maximum strength of surface winds associated is about 130km/h, slightly weaker than earlier estimates of 160 to 170km/h. This wind speed could still damage buildings and boats and the accompanying heavy rain could lead to flooding.

“Sea conditions along the southern Mozambican coast are forecast to be very rough, in the order of six to eight metres, while the additional threat of marine storm surge will be particularly pronounced on the forward flank (south-western) side of the system (due to the combined effect of storm motion as well as winds swirling clockwise around the system).

Assuming landfall near Msinga and Inhambane, the coastline north of Xai-Xai will be particularly vulnerable to storm surge.”

According to Rae, Dineo is expected to migrate due west along 23 degrees south latitude tomorrow, as a significant rain-bearing system but will start to weaken significantly.

“Notwithstanding this, it is expected that much of southern Mozambique can expect very heavy rainfall, most likely in the region of 100 to 200mm per day (or even more).

Bearing in mind that the lower portion of the Limpopo River flows directly through the Mozambican region that is most likely to be severely affected, this compounds the risk of flooding for communities which may possibly be displaced by this event.

It is important to keep in mind that all such tropical systems (such as tropical storms and tropical cyclones), which originate over open water, are critically dependent on the open ocean as a source of latent heat energy in order to sustain their growth and intensification. The moment such systems move overland (as is the case with Dineo later today), they invariably undergo rapid structural weakening and decay.”

In terms of Dineo’s impact on South Africa, heavy rainfall can be expected in the northern Lowveld and parts of Limpopo tomorrow evening.

“The greatest impact, with respect to South African provinces, is suggested to be overnight Thursday and into the morning hours of Friday, 17 February, when heavy rain can be expected over the entire eastern half of Limpopo (including the Kruger National Park), where 100 to 200mm of rain could occur per day. By early Friday morning the surface vortex (core) of Dineo should begin dissipating in the region of Musina and Beit Bridge in the northern part of Limpopo province.

By Saturday, 18 February, the remnants of Dineo are expected to drift into Botswana and showers are expected to continue over Limpopo Province.

Rivers in the region will continue to flow quite strongly in the latter part of the weekend and into next week, as overland runoff takes some time to enter river systems.”

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