# Tropical Storm Prapiroon (2024)

Severe Tropical Storm Prapiroon (Thai: พระพิรุณ), known in the Philippines as Tropical Depression Butchoy was a compact tropical cyclone that made landfall in Hainan and Vietnam in late July 2024. It was the fourth named storm of the annual typhoon season. Prapiroon was first identified as an area of persistent convection southeast of Manila, Philippines, on July 15. Several days later, the low-pressure system crossed into the South China Sea. As the storm progressed northwestward along the southern edge of a mid-level subtropical ridge, it intensified into a tropical storm and was named Prapiroon by the Japan Meteorological Agency (JMA) around 00:00 UTC on July 21. However, a few hours later, wind shear and dry air entrainment began to affect the storm. Despite this, deep convection continued to build around the center over the next six hours, resulting in a compact system as it approached Hainan. Prapiroon made landfall near Wanning, Hainan, with winds of 95 km/h (60 mph). After making landfall, the storm maintained its well-defined eye while moving across central Hainan, leading the JMA to upgrade it to a severe tropical storm at 00:00 UTC on July 23. On July 22, the JMA estimated peak 10-minute sustained winds of 100 km/h (65 mph) and a minimum barometric pressure of 985 hPa (29.09 inHg). Despite having persistent deep convection over its center earlier, Prapiroon soon encountered high wind shear and a dry environment. By the same day, it made its second landfall in Quảng Ninh, Vietnam, becoming the first tropical cyclone to strike Vietnam in 640 days. The JMA indicated that the storm dissipated, marking the end of Prapiroon's time as a tropical cyclone on July 25.
Prapiroon and its precursor, Typhoon Gaemi, affected the southwest monsoon over the Philippines, leading to significant rainfall across parts of the archipelago as Prapiroon began to move away. In China, twelve counties and cities on the island received rainfall over 100 mm (3.9 in). The remnants of Prapiroon also caused heavy monsoonal rains in parts of Thailand and Cambodia. Overall, the tropical storm was responsible for 23 deaths, 9 missing, and US$32.9 million in damage.

## Meteorological history

The origins of Severe Tropical Storm Prapiroon can be traced back to July 15, when the Joint Typhoon Warning Center (JTWC) reported an area of convection roughly 623 km (385 mi) southeast of Manila, Philippines. At that time, the disturbance was in a favorable environment for development, with warm 29–30 °C (84–86 °F), sea surface temperatures, low wind shear and good equatorial outflow. At 00:00 UTC the same day, the Japan Meteorological Agency (JMA) designated the system as a low-pressure area. Several days later, the low crossed into the South China Sea. On July 19, the JTWC gave a tropical cyclone formation alert to the disturbance, citing a high chance of development. At 21:00 UTC that day, the JTWC began issuing advisories on the system, classifying it as Tropical Depression 04W after convective bands had wrapped around a partially exposed low-level circulation center. The Philippine Atmospheric, Geophysical and Astronomical Services Administration declared the system a tropical depression a few hours later. Since the storm formed within the Philippine Area of Responsibility, the agency named it Butchoy. The following day, the JMA designated it as a tropical depression. As the storm progressed northwestward along the southern edge of a mid-level subtropical ridge, it intensified into a tropical storm and was named Prapiroon by the JMA around 00:00 UTC on July 21; however, a few hours later, wind shear and dry air entrainment began to affect the storm, yet deep convection continued to build around the center over the next six hours, resulting in a compact system as it approached Hainan.
A nascent eye feature became visible on microwave satellite imagery, while the associated central dense overcast grew more intense and displayed convective banding features. Around 16:00 UTC, the center of Prapiroon made landfall near Wanning, Hainan, with winds of 95 km/h (60 mph). After making landfall, the storm maintained its well-defined eye while moving across central Hainan, leading the JMA to upgrade it to a severe tropical storm at 00:00 UTC on July 23. On July 22, the JMA estimated peak 10-minute sustained winds of 100 km/h (65 mph) and a minimum barometric pressure of 985 hPa (29.09 inHg). Despite having persistent deep convection over its center earlier, Prapiroon soon encountered high wind shear and a dry environment, and by 6:30 a.m. local time that same day, it made its second landfall in Quảng Ninh, Vietnam, becoming the first tropical cyclone to strike Vietnam in 640 days. During the 2023 season, no tropical cyclone had made landfall in mainland Vietnam, making it the third instance since the country's independence, following the 1976 and 2002 seasons. After the system moved inland, the JTWC ceased monitoring it as a tropical cyclone at 18:00 UTC on July 24. The JMA indicated that the storm dissipated, marking the cessation of Prapiroon's time as a tropical cyclone the following day.

## Preparations and impact
### Philippines

Along with Typhoon Gaemi (Carina), Prapiroon and its precursor influenced the southwest monsoon over the Philippines, producing heavy rainfall over parts of the archipelago from July 12 through July 20, when Prapiroon began to move away from the Philippines. A total of 866,483 people were affected by the storm across the Mimaropa, Caraga, and Bangsamoro. About 33,645 people were evacuated to emergency shelters. There were 94 damaged residences in Mimaropa, of which 10 were completely destroyed. A total of 73 sections of road were damaged, and five bridges were damaged, while seven roads and a bridge were inaccessible. In Mindanao, a total of 179,744 households were impacted by heavy rainfall.
As of July 22, 2024, the National Disaster Risk Reduction and Management Council reported that 852,765 people were affected by Prapiroon, along with the impacts of the southwest monsoon. This resulted in 15 cities experiencing power outages and 149 houses damaged, along with at least eight fatalities and one missing person, as well as two injuries. Agricultural damage reached ₱8.75 million (US$177,582.2), while infrastructure damage was estimated at ₱700,000 (US$14,213.2), leading to a total damage of ₱9.45 million (US$191,795.4). Following the storm, about ₱29 million (US$496,173) worth of aid was distributed to 23,157 affected households. A state of calamity was declared in the municipalities of Pikit and Kabacan in Cotabato.

### China and Hong Kong

Prior to its landfall, the China Meteorological Administration issued typhoon and rain warnings along Hainan and Guangdong. A Level 3 out of 4 emergency response alert was issued in Guangxi, as well as a yellow typhoon alert. About 26,000 visitors on Weizhou Island were evacuated prior to the storm through the use of ferries. High-speed rail and ferry services on the island of Hainan were cancelled. All vessels in Hainan were ordered to return to port and offshore workers were allowed to seek shelter on the island. A flood control team was sent to Hainan in preparation for flooding. A No. 1 Typhoon warning signal was issued by the Hong Kong Observatory for Hong Kong, from the afternoon of July 20 to noon on July 22.
As Prapiroon made landfall in Hainan, twelve counties and cities on the island received rainfall in excess of 100 mm (4 in). The highest sustained wind measured on Hainan was 137 km/h (85 mph) in Wanning, where the storm made landfall. High winds were reported in Guangxi, reaching a peak of 89 km/h (55 mph) in Beihai. Torrential rainfall also impacted the province with a maximum accumulation of 38.3 mm (1.5 in) in Donglan County. Rain squalls impacted the Pearl River Delta, where occasional high wind gusts were reported in elevated parts of Hong Kong.

### Vietnam

Before Prapiroon approached Vietnam, Prime Minister of Vietnam Phạm Minh Chính ordered emergency measures to take place in coastal provinces. Vessels were ordered to return to port or move away from areas within the storm's projected track. Emergency response teams were deployed to protect traffic moving through flood and landslide-prone areas and assist in evacuation and recovery efforts. Measures were also taken to prevent dams and reservoirs from overflowing. Heavy rainfall was expected in Northern Vietnam, reaching as high as 300 mm (12 in) in parts of Thanh Hóa province.
As the storm landed in Quảng Ninh, Prapiroon became the first tropical cyclone to strike Vietnam in 640 days, ending a record drought of landfalls. The storm downed trees and damaged billboards and fences in the province of Quảng Ninh. Heavy rain and flooding in Sơn La Province killed seven people and two in Dien Bien Province, with nine others missing. Prapiroon brought significant agricultural impact to Vietnam. In the Cà Mau province and the Hậu Giang province, over 1,000 hectares of rice were damaged due to the heavy rains caused by Prapiroon. In the Trần Văn Thời district, 570 hectares of rice were damaged. As of July 29, damage by the storm and flooding in Son La Province reached 315 billion dong (US$13.36 million); and in Chuong My District in Hanoi reached 92 billion dong (US$3.9 million). In Dien Bien province, damage by the flooding, as of July 30, reached 30 billion dong (US$1.27 million).

### Elsewhere

In Thailand, the remnants of Prapiroon caused heavy monsoonal rains in some parts of the country. People were advised to be alert for dangers such as flash flooding and landslides. The combination of moisture from Prapiroon and Typhoon Gaemi produced severe thunderstorms across Cambodia, which resulted in strong winds, heavy rainfall, and lightning. A large tree fell onto a tuk-tuk in Siem Reap, killing five people and injuring four others. Local authorities cleared the scene of debris and were ordered to control traffic in an effort to prevent further vehicular incidents. In Laos, the remnants of Prapiroon alongside some subsequent depressions would cause LAK318 billion (US$14 million) in damage.