Extreme rainfall in “dry season” [1]
Friday, August 21, 2020 - 19:52. Updated on Friday, August 21, 2020 - 19:56.
Southern Tonga has experienced extreme rainfall this week that was close to the record, for this time of year in the “dry season”.
Climate Officer Selu Finau Lahi said today the downpour “was definitely extreme rainfall, not a record - but if you look at a 24 hour period it's close to a record in August.”
Between 10:00am Wednesday and 10:00am Thursday 79.5mm of rainfall was recorded at Fua'amotu Airport. This followed 35.5mm recorded the previous day.
Meanwhile, Ha'apai recorded 127mm in the 24 hours before 1:00pm on Wednesday August 19 and another 62.1mm the following day.
July rainfall
This week's wet weather follows a month of extremely high rainfall recorded over Tongatapu and 'Eua in July.
The Tonga Meteorological service released its quarterly climate update today reporting that 311.5mm rainfall for 'Eua in July was three times more than the average of about 100mm for July.
At the same time Fua'amotu recorded 271.8mm, compared to an average of around 115mm for July. While Nuku'alofa recorded 231.5 mm compared to an average of about 100mm for July.
Niuatoputapu also recorded above average rainfall for three months from May to July.
During July the mean temperature was 24.1oC which was 0.7oC warmer than average. Highest maximum temperature was 31.6oC on July 21 in Niuafo’ou and the lowest minimum 11.70C in ’Eua on July 23.
La Niña alert
Tonga Met warned that there is a likelihood of La Nina developing in October-December 2020, which further increases the chances of above average rainfall across Tonga.
“The El Niño–Southern Oscillation (ENSO) is currently neutral. However, continued cooling of the surface of the tropical Pacific Ocean, changes in tropical weather patterns, and climate model outlooks shifting further towards La Niña, which means the ENSO Outlook has moved to La Niña Alert.
La Niña Alert indicates the chance of La Niña forming in 2020 is around 70%. All international climate models surveyed suggest the tropical Pacific Ocean will cool further, with three of the eight models reaching La Niña thresholds in September and two more in October,” stated Tonga Met.
A La Niña Alert is not a guarantee that La Niña will occur, rather it is an indication that most of the typical precursors of La Niña are in place.
Tonga is currently in the Dry season now which runs from May 1 until the end of October 2020. It is the season when Tonga normally experiences less rainfall and cooler than average temperature.