As discussed last week, a cut-off low developed over the
Recent satellite imagery from the last 12 hours continues to show Tropical Storm Dineo organizing well in the Mozambique Channel. A large burst of convection took place over the center of the storm in recent hours, typical with a strengthening tropical storm, though majority of of the convection is located on the eastern portion of the storm. With that said, the latest frames seem to indicate the start of some banding towards the south of the storm, which would improve the visible appearance even further. Dineo seems to be showing excellent inflow from the African continent and northern portions of the Mozambique Channel. Outflow at this stage appears a little limited, through has appeared more promising in latest frames of satellite imagery, suggesting the storm may begin to strengthen more steadily at this point.
The movement of the storm has been gradually westward, though latest vis loops also suggest the storm has begun its route towards the south-west. The GFS and the Euro model have come to more of an agreement on the timing of this storm, suggesting that somewhere early morning on Thursday the storm is likely to make landfall on the Mozambique coast. After landfall, the track becomes more uncertain too, with the GFS model bringing the remnants over the continent above the South African border, while the Meteo-France forecast shows the track of what’s left of the cyclone, then moving through Limpopo province.
Tropical Storm Dineo is near Tropical Cyclone status now, and I expect we will see an upgrade today from the mets over at Meteo France. The last official reports had Dineo (06:00z) had Dineo at 50kt with a central pressure estimated to be at 985hpa. Once the storm reaches 60kt, it will be upgraded to a Tropical Cyclone. Dvorak estimates are being used along with Satcon by the meteorological agencies to estimate the current strength, both of which have Dineo at 53kt (1-min average) currently. These pieces of software use satellite imagery to predict the strength of a storm based off its appearance. They are not always accurate, but when there isn’t sufficient ground data such as that from recon dropsonde, they are often used as guidance.
Over the next 12 hours it is likely for the storm to become a Tropical Cyclone, and continue to strengthen until landfall. Forecasts from Meteo France at this stage suggest that Dineo could reach winds of 90kt prior to landfall, meaning it will become what is known as an Intense Tropical Cyclone.
Once the storm moves on land, it will likely undergo rapid weakening as it moves westward over the continent, and winds associated with the storm should die down quickly. While the associated rainfall will continue for a couple days, before the remnants appear to be absorbed by a broad low pressure over Namibia.
For citizens of Mozambique, this storm could be deadly. It is likely to bring extremely heavy rain and life threatening flooding, and 90kt winds are enough to cause significant damage to make-shift houses. The models suggest massive rainfall totals for the country as it moves slowly westard as it weakens.
What it means for South Africa
Here in South Africa it’s looking likely that we will indeed experience some of the effects of the storm in our country. There is an outside chance for heavy rains along the extreme northern parts of KZN near landfall, early on Thursday. Though this is difficult to forecast as it would rely heavily on the structure of the storm at the time. Our most likely chance for rain from the storm exists in Limpopo and Mpumalanga. The GFS model, which suggests a more northerly track than the official trajectory, still has some heavy rains for both Limpopo and Mpumalanga.
It becomes very difficult to make accurate rainfall predictions on decaying storms, since it is heavily reliant on how the storms convection maintains itself once on land. Currently the GFS model doesn’t indicate the same massive totals it did for Limpopo yesterday, however this could easily change by the time the storm makes landfall and the best thing to do is remain vigilant and keep an eye out on the official forecasts. The South African Weather Service has already begun issuing D3/D5 warnings for heavy rain and flooding for the Limpopo and Mpumalanga provinces.