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BEIJING - The national observatory on Thursday issued a blue alert, the lowest level of a four-tier warning system, for Aere, the 19th typhoon of the year.

Aere was upgraded from a tropical depression to a typhoon at 8 am Thursday, the National Meteorological Center (NMC) said in a statement.

At 3 pm, the eye of the typhoon was above the South China Sea some 530 km to the southeast of Hong Kong. It will move west at a speed of 15 km per hour, the center said.

The NMC said the typhoon will travel toward the coasts of Hainan and Guangdong provinces.

China has a four-tier color-coded system for severe weather, with red being the most serious, followed by orange, yellow and blue.