AWIO20 FMEE 191145 TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

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

DATE: 2015/12/19 AT 1200 UTC

PART 1: WARNING SUMMARY: Nil.

PART 2 : TROPICAL WEATHER DISCUSSION: The tropical Indian Ocean remains in Double Near Equatorial Trough pattern (DNET). The southern hemispheric branch of the DNET is axed 6S/55E, 10S/78E, 10S/90E.

Deep convective activity is patchy and located along the NET, but also in the Mozambique channel south of the Comoros archipelago and between the Mascareignes archipelago and the Malagasy coastline.

From the middle of next week, the ECMWF ensemble forecast and deterministic NWP model suggest the deepening of a low in the eastern part of this near equatorial area. This forecast is to be confirmed in the following advisories.

In the Mozambique channel, from Sunday evening, some NWP models (the ECMWF one among them) and a few members of the available ensemble forecasts still suggest the development of a weak low North of the Juan de Nova Island, near a low level convergence axis between the southerly trade winds and the northerly monsoon flow. This weak system is then brought closer to the Southeastern Malagasy coastline while tracking Southeastward. On Tuesday, it disappears as it makes landfall. The forecast precipitations on the Malagasy coastline are not very significant. Along this track, the upper level conditions are not very conducive for a further significant development as a Northwestward constraint is settling in as soon as Sunday evening. The ECMWF ensemble forecast does not suggest a cyclogenesis signal on this area.

On the basin, the likelihood of development of a tropical depression is very low for the next 5 days.

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

Very low: less than 10% Moderate: 30% to 50% Very high: over 90% Low: 10% to 30% High: 50% to 90%

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