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Tropical Cyclone outlook expects two cyclones for Tonga in season

Nuku'alofa, Tonga

There is a 75% chance of at least two tropical cyclones will occur during Tonga's 2018/19 cyclone season which started on November 1 to end on April 30, 2019.

This means that tropical cyclone activity expected this season to affect the country is likely to be average to above average, stated a 2018-19 Tropical Season Outlook released on October 30 by the Ministry of Meteorology (MEIDECC).

Although historical records indicated there could be a low chance of severe tropical cyclones occurring this season, citizens were advised to expect the likelihood of at least one severe cyclone occurring due to climate variability brought about by global warning.

The peak time for the occurrence of tropical cyclones in Tonga is from January to March with most events occurring in February.

Any tropical cyclones passing close to the country, associated active cloud and rain bands may occasionally affect Tonga with marked rainfall and possible flooding, including sea flooding of low‐lying coastal areas.

With the expectation of tropical cyclone formation (genesis) to lie east of the Dateline, there is high chance that any tropical cyclone affecting Tonga would approach from the northwestern and northern sector.

This cyclone season about seven to nine named Tropical Cyclones are expected for the South West Pacific in 2018/2019 season, consistent with some pre-season traditional weather indicators like moderate to heavy flowering and fruiting of breadfruit.


It was noted that tropical cyclones have occasionally formed outside this period like Tropical Cyclone Keli, which affected northern Tonga in June 1997. 

International forecast guidance in the last few months indicate there is an approximate 70% chance of a weak El Niño development during the 2018/19 tropical cyclone season. Therefore, there is a moderate chance that below average rainfall conditions could be expected during the tropical cyclone season.

The Ministry also cautioned that the information provided is only to be used as guidance and the given range of tropical cyclone numbers is indicative only. It is expected that the total number of tropical cyclones could be in the vicinity of the listed values, and not necessarily within the given range.

The values are the most likely number of tropical cyclones based on statistical and scientific evidence, including the influences by regional and global weather and climate variability drivers and indices.

“All communities should remain alert and prepared throughout the 2018/19 Tropical Cyclone Season and take heed of tropical cyclone alerts, warnings and advisories seriously whenever it is issued to reduce the effects on life and property. All are urged to be vigilant and follow forecast information provided by the Meteorology Department throughout the season.”

Tonga was affected by two Tropical Cyclones earlier this year, severe Tropical Cyclone Gita in February followed by a category 2 Tropical Cyclone Keni in April.