In the last few days, Jakarta and Bali have been showered with rain and strong winds, even though it is already the dry season. Some said the La Nina phenomenon caused the heavy rainfall.
So, is La Nina truly the culprit behind this unusual weather pattern? La Nina, a global climate anomaly characterized by cooler sea surface temperatures in the central and eastern tropical Pacific Ocean, is known to bring increased rainfall to east and central Indonesia during September, October, and November.
Indonesia’s Meteorology, Climatology and Geophysics Agency (BMKG) also explained.
BMKG said the peak of the dry season in most parts of Indonesia will occur in July and August 2024. During that period, rain is still common in many areas.
“It is true that most of Indonesia’s territory occurs in July and August 2024. However, this does not mean that in the dry period, there is no rain at all, but there is rain even though the range is below 50 mm/day,” said BMKG Head Dwikorita Karnawati.
Dwikorita said that in the next week, there is still potential for a significant increase in rainfall in several Indonesian regions. This phenomenon is caused by substantial regional-global-scale atmospheric dynamics.
She mentioned several factors, including the activity of the Madden Julian Oscillation (MJO) phenomenon and Kelvin and Rossby Equatorial Waves in most parts of Java, Kalimantan, Sulawesi, the Maluku Islands, and most of Papua.
Rossby waves are cold air currents that are normally polar jet streams. However, a number of factors can influence the motion of the polar jet stream to become more wavy than normal.
Meanwhile, Kelvin waves occur due to warm air currents circulating in the tropics, mainly moving eastward and with a direction of motion parallel to the equator.
In addition, warm sea surface temperatures in the waters around Indonesia contribute to providing conditions that support the growth of significant rain clouds in the Indonesian region.
Extreme weather: hail in Depok, Indonesia
A viral video on social media shows hail falling in the Sawangan area, Depok, on June 3, 2024.
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BMKG Deputy for Meteorology Guswanto confirmed this. According to Guswanto, the leading cause of hail is similar to regular rain, namely cumulonimbus (CB) clouds that form due to solid lifting or convex forces in the region.
The ice formed from this event is generally large. When a large collection of ice in the atmosphere begins to descend to a lower and warmer area, the ice begins to melt. Usually, the melted ice will become rain, but sometimes, there is also still ice.
“However, sometimes not all ice will melt completely and become hail,” said Guswanto.
To anticipate this uncertain climate, BMKG provides several recommendations:
- Do not litter
- Pruning fragile tree branches and twigs
- Strengthening poles and billboards is also necessary to prevent them from collapsing in strong winds.
