300
AWIO20 FMEE 021140

TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

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

DATE: 2020/10/02 AT 1200 UTC

PART 1:

WARNING SUMMARY:


Nil.

PART 2 :
TROPICAL WEATHER DISCUSSION:


The basin retains its winter configuration with trade winds that reach up to the equator. However, two areas of deep convection have been in place for a few days in the near equatorial zone: one appeared towards the Seychelles and has shifted eastward today between the Chagos and the Seychelles and the other is located on the extreme North-East of our basin. The filtering of wind anomalies at 850 hPa shows that associated with these thunderstorm areas, there is a signature of Kelvin waves (for the westernmo
st pole) and the Equatorial Rossby wave (for the easternmost pole).

Over the next 2 days, these two equatorial waves will cross over the eastern half of our basin and may participate in the formation of a low-level clockwise circulation even in the absence of a well-defined Near Equatorial Trough (NET) pattern. However, in an environment not really conducive for cyclogenesis (little or no convergence on the equatorial side, persistence of a moderate to strong vertical easterly windshear), there is only a very small risk that this initial disturbance could intensify into a t
ropical storm. There is currently no significant signal on the deterministic models, and the EPS and GEFS ensembles suggest a weak signal between Monday and Wednesday somewhere south of the Chagos Archipelago, whereas this minimum should generally move westward.

For the next 5 days, the risk of formation of a moderate tropical storm becomes very low from Monday over the central part of the basin.

NOTA BENE: The likelihood is an estimate of the chance of the genesis of a moderate tropical storm over the basin and 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.
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562
AWIO20 FMEE 031153

TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

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

DATE: 2020/10/03 AT 1200 UTC

PART 1:

WARNING SUMMARY:


Nil.

PART 2 :
TROPICAL WEATHER DISCUSSION:


The basin is still showing a winter pattern with trade winds reaching the equator. However, deep convection has been present for a few days in the near equatorial area in the extreme northeastern part of our basin. Related to equatorial waves activity, in particular an Equatorial Rossby wave (analysis based on wind anomalies at 850hPa), a circulation could be form in the eastern part of the basin within a building Near Equatorial Trough.

However, the environment remains globally unfavorable to cyclogenesis: little or no convergence on the equatorial side, persistence of a moderate to strong easterly vertical shear. At long range, these conditions could improve slightly with a decrease of the constraint and a better feeding inflow on the equatorial side. Chances for development of a storm cannot be totally excluded then.

For the next 5 days, the risk of formation of a moderate tropical storm becomes very low on Wednesday over the central part of the basin.

NOTA BENE: The likelihood is an estimate of the chance of the genesis of a moderate tropical storm over the basin and 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.
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