October 22, 2025 | 01:34 pm
TEMPO.CO, Jakarta - The weather across Java Island is undergoing a noticeable shift, from previously hot and dry conditions to warm and humid air. In several southern regions, the change is even more apparent, with temperatures turning cooler yet moist.
A researcher from the Climate and Atmosphere Research Center of the National Research and Innovation Agency (BRIN), Erma Yulihastin, explained that this transition is being driven by a combination of global and regional atmospheric factors occurring simultaneously.
“These changes are happening simultaneously,” Erma told Tempo on Wednesday, October 22, 2025.
Earlier in October, Jakarta and Tangerang experienced extreme heat accompanied by strong winds. Temperatures reached 37 degrees Celsius, while wind speeds climbed to 41 kilometers per hour.
Erma said this earlier dry and hot spell was caused by the formation of two tropical cyclone seeds in the northern hemisphere — Cyclone NAKRI in the Philippine Sea and System 96W in the Pacific Ocean near northern Papua.
Three Main Factors Behind the Weather Shift
BRIN's Erma identified three key causes behind Java’s current warm and humid conditions:
1) Active Madden-Julian Oscillation (MJO)
The MJO wave, which moves eastward across the tropics, is currently in Phase 4, located over the western part of Indonesia.
“This strong and active MJO is predicted to persist until October 27 before shifting eastward to Phase 5,” Erma explained.
The MJO enhances cloud formation and increases humidity, leading to more frequent rain.
2) Formation of Tropical Storm 95S
A tropical storm named 95S formed over the Indian Ocean near Sumatra on October 21, bringing sustained winds of up to 45 kilometers per hour. This system contributes to increased air moisture moving toward western Indonesia.
3) Negative Indian Ocean Dipole (IOD)
A strong negative IOD phase is amplifying the transport of cloud clusters from the Indian Ocean toward Java. This phenomenon tends to bring more rainfall to Indonesia, particularly during transitional seasons.
Sea Surface Warming Adds to the Impact
Erma noted that these atmospheric factors are being reinforced by warmer sea surface temperatures south of Java. The warmer waters provide additional energy and moisture, fueling cloud formation and rainfall.
“The spread of cloud clusters from the Indian Ocean to Java will effectively produce massive and uniform rains in the late afternoon to evening across most parts of the island,” she said.
What the Public Should Watch Out For
Despite the recent humidity, hot conditions may still dominate in the mornings and midday, before heavy rain falls in the afternoon.
Erma advised residents to stay alert and prepared for sudden weather changes.
“People should be aware of rapid shifts, from intense heat to overcast skies and heavy rain — by carrying umbrellas and raincoats when traveling,” she said.
Editor’s Choice: Microplastics Detected in Rainwater Worldwide, Not Only in Jakarta
Click here to get the latest news updates from Tempo on Google News
Microplastics Detected in Rainwater Worldwide, Not Only in Jakarta
1 hari lalu
A study in China this year indicated that the concentration of microplastics was markedly higher in snow than in rainwater.
BMKG Forecast for Greater Jakarta Today: Partly Cloudy with Chance of Rain
2 hari lalu
According to BMKG, the transition of seasons from early to mid-October is marked by hot and scorching weather in many regions.
Jakarta Responds to Microplastics Found in Rainwater
2 hari lalu
The Jakarta Environmental Agency stressed that the discovery of microplastics in the city's rainwater serves as an environmental alarm.
Best Places to Visit in Java: From Popular Spots to Hidden Gems
2 hari lalu
Discover the best places to visit in Java, where ancient temples, volcanic wonders, and tropical escapes meet vibrant cities and cultural treasures.
Jakarta Rain Found Contaminated with Microplastics, BRIN Study Shows
5 hari lalu
Microplastic pollution not only contaminates land and sea, but also the atmosphere. BRIN found an average of 15 microplastic particles in rainwater samples.
BRIN Research Advances AWD Electric Vehicle Technology
6 hari lalu
The National Research and Innovation Agency (BRIN) is developing advanced electric vehicle (EV) technology featuring an All-Wheel Drive (AWD) system.
BMKG Warning: Hot Weather to Persist Across Java Until Early November
6 hari lalu
BMKG attributes the hot weather, especially notable during the day and night, to a combination of the sun's apparent movement.
Why Indonesia's Temperatures in Urban Regions Are Rising
7 hari lalu
The ideal average maximum temperature for Indonesia's urban regions is 31-34 degrees Celsius, a range recently exceeded by recorded temperatures.
Scorching Heat in Jakarta, BRIN: Stay Alert for Evening Rainfall
7 hari lalu
Scorching heat with strong gusts has been affecting Jakarta and Tangerang in the last few days.
BMKG Forecasts Rain for Parts of Jakarta and Surrounding Areas
8 hari lalu
BMKG predicts there is potential for light intensity rain in a number of areas on Tuesday, October 14, 2025.
