13th June,2019 The Tropical Cyclone Season for 2018 – 2019 for Tonga is now officially declared to have ended. The climatological timeframe for tropical cyclone seasons in the South West Pacific region is from November to April. Typically, the tropical cyclone season starts on the 1st November, 2018 and ends on the 30th April, 2019. However, Tropical cyclones could still develop before or even after the normal climatological time-frame for the tropical cyclone season. These occurrences would still be counted towards the season’s total in our Area of Responsibility (AoR) of the Tonga Meteorological Services.
Summary
The Tropical Cyclone (TC) season 2018-2019 for Tonga was above average, given the El Nino status of this year. On average, during El Nino years, Tonga would expect 2 Tropical Cyclones to occur. This season has produced a swarm of extreme tropical weather systems for Tonga. A total of 7 Tropical Depressions (TD): TD03F, TD04F, TD06F, TD07F, TD08F, TD10F and TD11F. From the formation of these 7 consecutive Tropical Depressions, 3 of these systems reached Tropical Cyclone status and strength. Tropical Cyclone Mona: Category 1 (TD04F), Tropical Cyclone Neil: Category 1 (TD07F) and Severe Tropical Cyclone Pola: Category 4 (TD11F). It is to be noted that the occurrences of these extreme tropical weather systems was known to be above average for Tonga during this past Tropical Cyclone season.
In the light of the Tropical Cyclone outlook for the TC Season 2018-2019 that was released on the 30th October, 2018. It was predicted that an increased likelihood of about 75% chances of at least 2 to 3 Tropical Cyclones was expected to occur within the Area of Responsibility of the Tonga Meteorological Services during this TC season. From these predicted 2 to 3 Tropical Cyclones, 1 Tropical Cyclone would reach Severe status at Category 3 or above. The occurrences of these swarm of extreme tropical weather system in our Area of Responsibility serves to justify that the Tropical Cyclone Outlook released prior to the start of this TC season was fairly consistent and accurate in comparison to the actual events that was experienced during this past TC Season.
Majority of these extreme tropical weather systems were concentrated and had tracked passed to the Western peripherals of the Kingdom of Tonga. These Westward bounded systems included Tropical Cyclone Mona (TD04F), TD06F, TD07F, TD08F,TD10F and Severe Tropical Cyclone Pola (TD11F). It was only TD03F and Tropical Cyclone Neil (TD07F) that moved into a different trajectory between the maritime waters and land areas of Tongatapu and the Ha’apai group.
A record was also being set during the operational working hours of this TC Season 2018-2019 in regards to the occurrences of these swarm of extreme tropical weather systems (TD 06F,07F,08F and 10F) was that the Fua’amotu Tropical Cyclone Warning Centre (FTCWC) of the Tonga Meteorological Services under MEIDECC was activated for a record of 6 consecutive days and 16 hours from 2:00pm 06th February, 2019 to 06:00am 13th February, 2019. This is the longest period that the FTCWC has operated non-stop since it’s establishment on 11th September, 2007. The previous record was 6 consecutive days and 12 hours during Severe Tropical Cyclone Ian that affected the Ha’apai group in 2014. It was also the first time for Tonga to experience and to be affected by 4 consecutive tropical systems one after the other.
Although the occurrence of such events is rare, these swarms of tropical cyclone activity are possible. “They often occur during El Nino or near El Nino years and has happened before during the 2004-2005 cyclone season in the Cook Islands where they we hit by 5 tropical cyclones in the span of 3 weeks”, said the Acting Director of the Tonga Meteorological Service Mr. Laitia Fifita.
Off Season Tropical Cyclones was also experienced during this past TC Season as it was experienced in the development of TC Liua (Category 1) on the 26th September, 2018 in the regions of the Solomon Islands. Tropical Cyclone Ann (Category 1) which developed on the 7th of May, 2019 in the regions of New Caledonia, then later tracked Westwards to Queensland. The last extreme tropical weather system to develop off season was TD 12F which had developed between 16th – 18th May, 2019 in the waters North of Rotuma (Fiji) but did not further intensify into Tropical Cyclone status. All these off season developments did not affect or tracked into our Tonga areas.
Above all, the Tonga Meteorological Services of MEIDECC wishes to thank the people of Tonga and all relevant stakeholders for the continued collaborations, support and taking into consideration all the necessary Tropical Cyclone warnings and advisories that were being issued from the Tonga Met Office during this past season, for decision making for the ultimate safety of lives and properties of the people of Tonga. The FTCWC is now officially de-activated and will resume Tropical Cyclone Operations in five months ,prior to the start of another new Tropical Cyclone Season (2019-2020), on the 1st of November, 2019.
ENDS
Issued by the : P.O.Box 1380, Nuku’alofa, TONGA; Tel (676) 28 170; Fax (676) 24 861; Email; fmt@met.gov.to; URL www.met.gov.to