AWIO20 FMEE 291147
TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

BULLETIN FOR CYCLONIC ACTIVITY AND SIGNIFICANT TROPICAL WEATHER
IN THE SOUTHWEST INDIAN OCEAN

DATE: 2025/04/29 A 1200 UTC

PART 1: WARNING SUMMARY

NIL.

PART 2 : TROPICAL WEATHER DISCUSSION:

The basin depicts a Near Equatorial Trough (NET) pattern east of 58E, undulating slightly between 4 and 7S. Convective activity is mostly located over the southern Mozambique Channel under a cut-off, while developing along the Tanzanian and Malgasy coasts.

The large-scale context remains unfavorable to cyclogenesis overall. This is due to the current dry phase of the MJO in the eastern part of the Indian Ocean, and the positive phase of the IOD, which will generate an anomaly of near-equatorial easterly winds capable to weaken the current NET over the week. However, until Friday, a Kelvin wave will intersect with an equatorial Rossby wave in the Diego-Garcia area. This short-lived wave interaction could very occasionally reinforce the low level vorticity, without being totally effective.

Area of low pressure north of Diego Garcia :
A large area of low pressure is currently located to the east of Diego-Garcia. Analysis of the ASCAT pass from 0530TU shows an ill-defined circulation with maximum winds up to 25 kts in the eastern part of the gradient flow. 

The lack of low-layer convergence, especially on the polar side, induced by undulatory activity is highly unfavorable. All deterministic and ensemblistic models, suggest no significant deepening in this area, except one or two outliers from the European ensemble.

Over the next 5 days, there is no risk of a moderate tropical storm forming in the basin.

Suspect area off the east coast of South Africa :

A minimum under a cut off is taking place near from the border between Mozambique and South Africa. 

By Thursday, deterministic models predict a baroclinic deepening moving south-southeastward. Despite intensifying winds, the minimum is unable to gather tropical characteristics (symmetrical warm core, deep convection). On Thursday, this low will move rapidly below the 40S characterized by a zone of strong shear.

Over the next 5 days, there is no risk of a moderate tropical storm forming in the basin.





NOTA BENE: The likelihood is an estimate of the chance of genesis of a moderate tropical storm over the basin within the next five days:

Very low: less than 10%      Moderate: 30% to 60%      Very high: over 90%
Low: 10% to 30%              High: 60% to 90%

The Southwestern Indian ocean basin extends from the Equator to 40S and from the african coastlines to 90E.