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Division of tropical storm increases uncertainty of impact: CWB

2019/07/17 16:29:30

From Central Weather Bureau

Taipei, July 17 (CNA) A division in the structure of Tropical Storm Danas will make it more difficult to predict the development of the weather system above Taiwan, the Central Weather Bureau (CWB) said Wednesday.

Danas divided into two systems Tuesday evening when its periphery hit Luzon in the Philippines, forecasters said.

The terrain of the island broke the storm from about 3km above sea level, turning it into two systems 0-3km and 3-10km in elevation, respectively.

The lower, stronger system remains the core of Danas, which as of 4 p.m. Wednesday was 400km southeast of Taiwan's southernmost tip, moving in a northwesterly direction and expected to skirt northeastern Taiwan late Thursday or early Friday.

Meanwhile, the higher system moved to waters west of the Philippines and could develop into a tropical depression by Thursday, according to the bureau.

"There is room for the new weather system to grow because it is within a bigger depression zone, which provides favorable conditions for its development," said forecaster Chen Yi-hsiu (陳伊秀).

As it is now possible Taiwan could be simultaneously impacted by both the tropical storm and a tropical depression from late Wednesday at the earliest, there is increased uncertainty as to how the two systems will interact and affect the country, she said.

The most likely outcome is that Danas will pull the new system closer to Taiwan, although it is not clear in which direction it could move.

Whether the new depression moves up through the Taiwan Strait or into waters off eastern Taiwan, the interaction between the two systems is highly likely to bring torrential rain to central, southern and eastern Taiwan on Friday, she said.

The rainfall is expected to be even heavier than that brought by Danas alone when it moves closest to Taiwan, according to Chen.

The division of the storm is not uncommon, Chen said, but added that the situation dose not quite constitute a "Fujiwara effect," when two nearby storms orbit each other, spiral into a point between them and eventually merge.

In the case of Danas, both weather systems are likely too weak for that to happen, she added.

(By Lee Hisn-Yin)