22 tropical cyclone alerts in a week, a first for Tonga Met [1]
Friday, February 15, 2019 - 20:15
In the span of one week, Tonga experienced a rare occurrence of four extreme tropical weather systems, one after another passing through the group, when Tonga Met issued 22 six-hourly tropical cyclone alerts and seven three-hourly tropical cyclone warnings, over a record six days and 16 hours, between 2pm on 6 February to 6am on 13 February.
Tonga Met Director, ‘Ofa Fa’anunu said this is the longest period the warning centre has operated non-stop since its establishment on 11 September 2007.
“The previous record was 6 days and 12 hours during Severe Tropical Cyclone Ian that affected Ha’apai in 2014.”
“This is the first time I can recall over the 20 years I have worked at the weather office that four tropical systems have affected Tonga one after the other,” he said.
Three depressions (TD06F, TD08F and TD10F) passed west of Tonga, while Tropical Cyclone Neil (developed from TD07F) diverted and passed east of Tongatapu by about 50km.
‘Ofa said that although rare, groups of tropical cyclone activities are possible.
“They often occur during El Nino or near El Nino years and have happened before during the 2004/2005 cyclone season in the Cook Islands where they were hit by five tropical cyclones in the span of three weeks.”
To date, this cyclone season has been quite active with two cyclones and five tropical depressions affecting Tonga.
“But as expected, the systems have been small ones with maximum gusts recorded only 50kts,” said ‘Ofa.
“The Pacific has been very active in terms of cloudiness and producing tropical extreme weather systems in the last two weeks.”
Late March
Tonga Met expects the activity to calm down by the end of this week. But for the season, there is an expectation that the last active period to affect this part of the Pacific will be towards late March or early April.
A 75 percent chance of at least two cyclones affecting Tonga this cyclone season was earlier predicted by Tonga Met. While historical records indicate a low chance of severe tropical cyclones forming this season, there is a likelihood that at least one severe cyclone may occur due to climate variability caused by global warming.
“These predictions still stand,” he said.
The most cyclones Tonga has experienced in one tropical cyclone season was four in 1979/80, when Tropical Cyclones Leslie, Meli, Ofa and Tia affected Tonga.
During that year, the tropical Pacific sea surface temperature patterns were similar to the current season.