Southern Taiwan sees over 2 meters of rain in 7 days: CWA

Taipei, Aug. 3 (CNA) Around 2,000 millimeters of rainfall fell in parts of southern Taiwan from July 28 to 9 a.m. Sunday, the Central Weather Administration (CWA) said.

Kaohsiung's Taoyuan District saw total rainfall of 2,205 mm, while Sandimen Township in Pingtung County had 2,060.5 mm and Nanhua District, Tainan 1,833 mm, according to CWA data.

Meanwhile, Alishan in Chiayi County saw 1,688 mm of accumulated rain and Caoling Village in Yunlin County 1,025 mm.

The Pingtung County government said that 831 local residents have been preemptively evacuated from mountainous areas. A total of 576 are staying with relatives in low-lying areas while the other 255 are in shelters.

CWA forecaster Chu Mei-lin (朱美霖) said at a press briefing that three factors are contributing to the continuous intensive rainfall in southern Taiwan.

The first is successive southwestern air currents that formed over the ocean and moved landward, impacting the western half of the island and outlying Penghu County.

Secondly, southwesterly winds brought in unstable air that developed into convection currents over land and resulted in rain.

Lastly, the southwesterly winds sweeping into southern Taiwan's mountainous topography caused orographic rainfall, causing intense rain in the region's mountainous areas, Chu said.

Orographic rain is produced when moist air lifts as it moves over a mountain range, cooling as it rises and forming clouds that produces rain upwind of the mountain ridge.

Chu pointed out that a large-scale low pressure system has been hovering over Taiwan since late July, resulting in persistent southwesterly winds.

The intense rain peaked once from July 28-31, with a second peak occurring over the weekend, she said

The CWA has issued precipitation warnings through Sunday to Monday morning.

Extremely torrential rain advisories have been issued for mountainous regions in Tainan, Kaohsiung and Pingtung County, where accumulated rainfall exceeding 500 mm in 24 hours is forecast, according to the CWA.

Torrential rain advisories, warning of rain exceeding 350 mm in 24 hours or 200 mm in three hours, have been issued for Tainan, Kaohsiung, Nantou County, Pingtung County, and mountainous areas in Yunlin County and Chiayi County.

Warnings of extremely heavy rain, defined as accumulated rainfall exceeding 200 mm in 24 hours or 100 mm in three hours, were issued for Taichung, Changhua County, Yunlin County, Chiayi County, the Hengchun Peninsula and mountainous areas in New Taipei.

Meanwhile, Taipei, New Taipei, Keelung City, Chiayi City, Yilan County, Hualien County, Taitung County, outlying Penghu, Orchid Island and Green Islands, as well as mountainous regions in Taoyuan and Hsinchu County received heavy rain advisories, warning of rain over 80 mm in 24 hours or 40 mm in one hour, the CWA said.