BMKG Predicts Dieng Upas Dew Phenomenon To Last For One Basis

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BANJARNEGARA - The Meteorology, Climatology and Geophysics Agency (BMKG) predicts the phenomenon of frost or frost that will begin to appear in the Dieng Plateau, Banjarnegara Regency, Central Java, on Thursday, June 30, early in the morning, to last for one day (ten days).

"Regarding the hail phenomenon, it is still related to the existence of two low pressure centers (LPA) in the northern hemisphere (BBU), namely the 04W low pressure center in the South China Sea west of the Philippines and the 98W low pressure center in the northeastern Philippines," he said. Head of BMKG Banjarnegara Geophysics Station Setyoajie Prayoedie, quoted by Antara, Thursday, June 30.

According to him, this condition is coupled with the strong Australian Monsoon (eastern wind) which brings dry air which has an effect on reducing rainfall in Java, especially Central Java, so that in a few days the weather conditions in Central Java tend to be sunny to cloudy.

However, this condition will last up to one month in July 2022 (1-10 July) and after that it will tend to be wet again (dry season) due to the influence of warm sea surface temperatures around Java and the La Nina climate anomaly with weak intensity with probability around 66 percent until the July-August 2022 period.

"So, it is still possible for this phenomenon to occur in the first basic period in July 2022," said Setyoajie.

Asked about the air temperature in Dieng when the dew appeared on Thursday, June 30 in the morning, Setyoajie Prayoedie said that based on observations it was around minus 1 degree Celsius at 04.00 WIB to 05.00 WIB.

Meanwhile, in a press release, Head of BMKG Class II Meteorological Station Ahmad Yani Semarang Sutikno said that according to residents of Dieng, upas dew is poison dew.

"This phenomenon occurs when the temperature cools down, then cold and frozen dew falls. This dew covers the potato plants and the Dieng people call it upas dew because its effect is to waste the dead potatoes," he said.

According to him, several factors contributed to the formation of frost that was preceded by extreme cold temperatures in Dieng, among others, the apparent motion of the sun, cold temperature intrusion, and the rate of decrease in temperature with altitude.

The occurrence of the upas dew phenomenon in the Dieng Plateau area in 2021 began in May, to be exact on May 10, 2021, the next on July 7, 2021 and the last news on July 15-16, 2021.

"Then in 2022, upas dew occurs earlier, namely in early 2022, to be precise on January 4, 2022. Then on June 30, 2022," said Sutikno.

He said the phenomenon of cold temperatures at night and frost on the slopes of the Dieng mountains was more due to meteorological conditions and the current dry season.

According to him, the air temperature during the peak of the dry season is generally cooler and the earth's surface is drier.

"In such conditions, more solar heat will be wasted and lost to space. That's what causes the dry season air temperature to be cooler than the rainy season air temperature," he said.

In addition, he said, the water content in the soil is thinning and there is very little water vapor in the air as evidenced by the low humidity of the air.

At the peak of the dry season in Java, some places that are at high altitudes, especially in mountainous areas, are indicated to have the opportunity to experience surface air conditions of less than freezing point 0 (zero) degrees Celsius, due to the air molecules in mountainous areas being more tenuous than in lowlands, so it cools down very quickly, especially when the weather is sunny and not covered by clouds or rain.

Water vapor in the air will condense at night and then condense to stick to the ground, leaves, or grass. Dew water that sticks to the tops of leaves or grass will immediately freeze because the air temperature is very cold.

"When it reaches minus or zero degrees, dew or frost occurs in the area. In Indonesia, several places have been reported to experience this phenomenon, namely the Dieng Plateau, Mount Semeru, and the Jayawijaya Mountains," said Sutikno.