PETALING JAYA: The heavy rain and thunderstorms over the past few days in several states are only temporary and do not signal the arrival of the northeast monsoon, say weather experts.
They said rain will continue for about a week before the temperature rises again for some time before the inter-monsoon season arrives in October.
Academy of Sciences Malaysia fellow Prof Dr Fredolin Tangang said the current wet weather conditions, especially over Peninsular Malaysia, could be associated with the influence of the Boreal Summer Intraseasonal Oscillation (Bsiso).
“On the west coast of the peninsula, availability of moisture due to Bsiso could enhance diurnal cycle, and this could drive wet weather conditions and thunderstorms we have been experiencing in the Klang Valley over the past few days,” he explained.
The climatologist noted that the Apec Climate Center (APCC) in Busan, South Korea, has also been issuing Bsiso forecasts, including rainfall for the next four weeks, using five different models.
Based on the forecasts on Aug 19, there is a high consistency among the models that the region may continue to experience wet weather conditions for another week or so.
“However, in the next two to three weeks, most models have forecasted dry conditions,” he added.
In a statement yesterday, the Malaysian Meteorological Department (MetMalaysia) stated that the wind concentration is expected to occur in Sabah and Sarawak while an increase in air humidity may bring heavy rain in the west coast, inland and Tawau (Sabah), and the central and southern areas of Sarawak.
It further said that thunderstorms, heavy rain and strong wind are expected in the late evenings and into the nights over most of the peninsular states as well as some parts of Sabah and Sarawak today.
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National Antarctic Research Centre climatologist Prof Datuk Dr Azizan Abu Samah said: “This heavy rain episode looks like its being influenced by the Madden Julian Oscillation (MJO) phase, which over our region is a westerly anomaly,” he said.
(The MJO is the largest element of the intraseasonal (30 to 90-day) variability in the tropical atmosphere.)
Prof Azizan pointed out that there are many drivers of rain that influence rainfall variability.
“The most obvious is the El Nino-neutral-La Nina that gives variability of a two to three-year cycle. After that, it’s the southwest-northeast monsoon, which is semi-annual.
“Our meteorological numerical model will incorporate all the variability in forecasting rainfall,” he said.
Prof Azizan said the forecast is is done up to 24 and 48 hours ahead.
“It is thus best for the public to take necessary precautions in regard to weather alerts,” he said.
He added that Malaysia has 265 rainy days in a year, ranking eighth as a water surplus country with 2m of rainfall in the peninsula and 4m in Sabah and Sarawak.
