KUCHING, Aug 28 — Thunderstorms that have swept parts of Sarawak in recent days may bring temporary relief from the haze, but the improvement is unlikely to last if hot and dry conditions persist and smoke sources remain active, said Malaysian Meteorological Department (MetMalaysia) Sarawak director Khairul Najib Ibrahim.
He said thunderstorms were a normal occurrence in tropical countries but could develop rapidly when atmospheric conditions became highly unstable.
The combination of intense daytime heat and Sarawak’s naturally high humidity had created conditions conducive to the formation of large convective clouds and localised thunderstorms, some accompanied by strong winds, he told The Borneo Post.
“Thunderstorms in tropical areas can develop very rapidly. A storm may appear relatively normal in the early afternoon but can develop into a storm producing strong winds within two to three hours,” he said.
Khairul Najib said the recent thunderstorms were therefore not necessarily unusual, despite Sarawak experiencing a generally hotter and drier period during the Southwest Monsoon.
He explained that Sarawak typically experienced drier conditions during the Southwest Monsoon, but surface temperatures over the past week had been higher than usual.
“This high daytime heat, combined with Sarawak’s natural humidity, has created highly unstable atmospheric conditions,” he said.
As hot and humid air rises, it forms large storm clouds that can produce thunderstorms and strong winds, he added.
Khairul Najib said haze particles in the atmosphere could also contribute to cloud formation by acting as nuclei around which water droplets could form.
On whether rainfall could disperse the haze, he said heavy rain could improve air quality and visibility by removing some smoke and dust particles from the atmosphere through a process known as wet deposition.
However, he cautioned that the improvement could be short-lived if the sources of smoke remained active.
“If the source of the smoke is still active, for example fires in Kalimantan, the haze can return because south-westerly winds can carry the smoke into Sarawak,” he said.
The explanation comes as Sarawak continues to experience hazy conditions following a prolonged period of hot and dry weather.
Earlier this month, Khairul Najib warned that prevailing winds and hotspots in neighbouring countries could contribute to transboundary haze, particularly in western and southern Sarawak.
Beyond the immediate haze situation and thunderstorms, he said the public should also prepare for the possibility of a prolonged dry spell.
Khairul Najib said Malaysia, including Sarawak, was currently experiencing moderate El Niño conditions, which could continue until at least April 2027.
More significantly, he said the latest projections indicated that the current El Niño could strengthen to a strong or “super” El Niño around October to December this year.
He said such a development could prolong the combination of hot and dry conditions, potentially exacerbating haze if fires and other sources of smoke remained active.
Khairul Najib advised the public to take appropriate precautions, follow instructions from the authorities and keep abreast of weather developments through reliable sources.
He also urged the public to remain vigilant during thunderstorms, which could intensify rapidly under highly unstable atmospheric conditions.
Sarawak had earlier been warned that drier conditions were expected to peak between June and August, coinciding with the Southwest Monsoon and the early influence of El Niño.
Khairul Najib said the current situation highlighted the contrasting weather conditions Sarawak could experience, with sudden thunderstorms occurring alongside a broader pattern of heat and dryness.
“While heavy rain may temporarily wash haze particles from the air, it does not remove the source of the smoke — nor does it signal the end of the underlying dry conditions,” he said. — The Borneo Post
