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Daily Tropical Weather Outlook (”ITCZ” bulletin)
World Meteorological Organization (WMO) header: AWIO20 FMEE
The Daily Tropical Weather Outlook or Bulletin for Cyclonic Activity and Significant Tropical Weather in the SouthWest Indian Ocean has two separate parts. Part 1 includes information about any current warnings related to active tropical systems on the basin. These current warnings and their associated numbers are those dedicated to the marine users (Marine Warning). Part 2 is a discussion of significant areas of disturbed weather and their potential for development into moderate tropical storms within the next 5 days.
Daily Tropical Weather Outlooks are issued all year round before 1200 UTC.
Example
AWIO20 FMEE 171043
TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE
BULLETIN FOR CYCLONIC ACTIVITY AND SIGNIFICANT TROPICAL WEATHER IN
THE SOUTHWEST INDIAN OCEAN
DATE: 2018/12/17 AT 1200 UTC
PART 1:
WARNING SUMMARY:
Warnings WTIO20 and WTIO30 FMEE n°004/4 issued at 06UTC on Severe Tropical Storm KENANGA.
Next warnings will be issued at 12UTC.
PART 2 :
TROPICAL WEATHER DISCUSSION:
Our basin is in a Monsoon Trough (MT) pattern over almost its entire width, oriented towards 9S.
Convective activity is moderate on the north side of the MT and in zone of disturbed weather 05S to the northeast of the Mascarenes. It is strong near severe tropical storm KENANGA.
Severe Tropical Storm KENANGA :
Position at 09UTC : 12.6S/87.1E
Movement: Southwest 10kt
Maximum mean winds : 50kt
Central pressure: 986hPa
Zone of disturbed weather 05S northeast of the Mascarenes:
The last ASCAT swath remain partial on this system. They confirm the presence of a clockwise circulation that is still elongated but is gradually becoming more concentrated with winds of around 20kt. Convective activity remains moderate. Data from the 0411UTC GPM satellite can be used to locate a centre at about 10°S/60°E.
Conditions will remain very favorable for an intensification of this system, with a decreasing wind shear and an improving convergence on the equatorial surface. In this favorable atmospheric environment and with a strong oceanic potential, this zone of disturbed weather is expected to intensify and reach the threshold of moderate tropical storm within two to three days.
After a track oriented south-west during cyclogenesis, the system should start a turn before the next WE towards the south-east under the influence of a deep upper-level trough. This track remains a threat to the Mascarenes according to most deterministic and ensemblists models, at the end of the next WE.
For the next 5 days, the risk of formation of a tropical storm becomes moderate from Wednesday and high from Thursday in the North-East of Mascarenes.
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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