AWIO20 FMEE 101107
TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

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

DATE: 2026/06/10 A 1200 UTC

PART 1: WARNING SUMMARY

NIL.

PART 2 : TROPICAL WEATHER DISCUSSION:

The basin is in a winter configuration. Convective activity is weak in the tropics and is confined to the northeastern part of the basin. A series of upper-level troughs over the southwestern part of the basin also supports moderate convective activity near the southern coast of Madagascar and southeast of South Africa.

This winter configuration adds to a large-scale low-frequency dry anomaly and sinking pattern over the Indian ocean, yielding durably unfavorable conditions for cyclogenesis in the tropics.

Possible subtropical system south-east of Madagascar :
A low has formed since Tuesday southeast of Madagascar due to baroclinic forcing associated with a deep upper-level trough. This low has moved southeastward over the past 24 hours and is currently located near 30oS. Satellite imagery and a partial ASCAT-B pass at 0346Z this morning show an asymmetric, multi-vortex structure with convection that remains moderate and poorly organized for the time being, primarily in the southeastern semi-circle of the circulation. The main rotation center appears to be located around 30oS/51oE. Winds measured by ASCAT-B are in the order of 30 kt in the eastern semi-circle. 
By Thursday, the low-pressure system will move under the upper trough's axis, between two jet stream branches, in a low wind shear environment. In the lower layers and mid-troposphere, warm air of tropical origin has been drawn into the low-pressure circulation from the northeast and is expected to become isolated in the form of a warm seclusion. This context should enable better convective organization and a symmetrization of the circulation over the next 24 hours. Deterministic models suggest a deepening of the low-pressure system and winds reaching up to 35-40 kt between Wednesday evening and Thursday morning. Nevertheless, the presence of a mid-level warm core does not appear to be convection-induced but rather results primarily from the seclusion process. Furthermore, dry air present in the mid-troposphere could wrap around the eastern flank of the system and limit convection, as suggested by forecast satellite images from various models. Starting Thursday evening and especially on Friday, increasing wind shear and dry air intrusions are expected to cause the system to weaken.
The formation of a subtropical storm therefore cannot be ruled out, even though chances remain quite low. In any case, this potential system would remain far from inhabited areas.

There is a low risk of subtropical storm development off the south-east of Madagascar until Thursday 11th.



10-day outlook:
Nothing to report.

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.