Tropical cyclone Eloise set to intensify | Possible impact on South Africa's weather

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The predicted track for “Eloise” over the next few days, as supplied by WMO RSMC La Reunion (MeteoFrance). The green shaded region represents the highest confidence region for the position of “Eloise”. This region expands and becomes larger, as uncertainty increases with increasing lead-time. “Eloise” is projected to be positioned south east of Beira, Mozambique by midday on Saturday 23 January 2021.  Courtesy: RSMC LaReunion
The predicted track for “Eloise” over the next few days, as supplied by WMO RSMC La Reunion (MeteoFrance). The green shaded region represents the highest confidence region for the position of “Eloise”. This region expands and becomes larger, as uncertainty increases with increasing lead-time. “Eloise” is projected to be positioned south east of Beira, Mozambique by midday on Saturday 23 January 2021. Courtesy: RSMC LaReunion
  • Tropical systems are notoriously fickle and unpredictable, often exhibiting very erratic movement
  • Eloise to intensify to a Severe Tropical Storm, with sustained winds likely to exceed 100km/h
  • There's much uncertainty surrounding the prediction of future development and movement of Eloise.

As a fresh tropical system named Eloise has developed and is currently positioned off the north-eastern quadrant of Madagascar, the SA Weather Services (SAWS) has issued a statement in which they said it has the potential to impact on South Africa's weather in days to come.

In a statement on Monday, SAWS said that at present, Eloise is classified to be a Moderate Tropical Storm, with a central pressure slightly less than 1000 hPa (hectopascal). But, the storm is set to intensify in the coming days.

Eloise is positioned at 14.2 degrees South and 56.7 degrees East, moving briskly at 14 knots (about 26km/h) in a west-south-westerly direction, said SAWS.

They believe that the most likely track the storm will follow should take it close to the coast of Madagascar tomorrow, as it intensifies further to a Severe Tropical Storm, with sustained winds likely to exceed 100km/h.

"Hence as Eloise makes landfall on this coastline in the latter part of tomorrow, it is likely to cause considerable wind-related damage, as well as delivering torrential rain. Given the steep geographic terrain of eastern Madagascar, flooding and washaways are also a distinct possibility. Moreover, along the coast there will also be a risk of storm surge, especially on the southernmost leading quadrant of the storm system. 

Severe Tropical Storm Chalane brought rain to southern Africa during the Christmas and New Year period last year.

"The good news is that, as Eloise moves across the landmass of northern Madagascar, it will be exposed to increased friction, as the winds interact with the rough land surface. Moreover, Eloise will be deprived of the latent heat energy which it would normally receive from a warm, tropical ocean. We can therefore confidently predict that Eloise will weaken significantly during this particular period."

But, that's not the end of Eloise's story.

SAWS said later in the lifecycle of Eloise, "it will without doubt begin to redevelop as it drifts back into the open ocean region of the Mozambique Channel this Friday".

"It will be at this stage that Eloise will require close monitoring, as it has the potential to make landfall along the southern Mozambican coastline, between Beira and Vilanculos during the coming weekend. Alternatively, Eloise could gradually begin to move on a more southerly parabolic path (often termed a “polewards-accelerating” trajectory), which could potentially take it further down the Mozambican coastline and possibly into the north-eastern lowveld region of South Africa. At the current time, the speculative possibility of Eloise directly affecting South Africa is only one of a multitude of possible outcomes, given the long lead-time, and should be considered to be a “low probability / high uncertainty” worst-case scenario."

SAWS emphasised that, as with any and every tropical system worldwide, there is much uncertainty surrounding the prediction of future development and movement of Eloise.

"Tropical systems are notoriously fickle and unpredictable, often exhibiting very erratic movement. Modern satellite remote sensing as well as advanced ensemble numeric modelling techniques do, however, mitigate much of this uncertainty, at least in the short-term."

Notwithstanding the above, the general public can rest assured that SAWS will continue to be vigilant and to closely monitor the future evolution of Eloise. Further timely updates in relation to Eloise will be issued as and when necessary.  

Note: SAWS corrected the wind speed from 50km/h to 26km/h in this version of the story.

    

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