Question number 9-10 based on the passage below.

    The Meteorology, Climatology and Geophysics Agency (BMKG) has predicted that the supermoon phenomenon, which will occur from Jan 19 to 22, 2019, will not significantly impact the southern coast of Yogyakarta. The agency announced here on Saturday, Jan 19, about the potential increase of sea waves on the southern coast of Yogyakarta due to supermoon phenomenon. However, the waves will not likely cause disruption to transportation and fishing activities. The BMKG explained that the supermoon phenomenon occurs when the full moon is closest to the earth, which is as far as 357,492 kilometers. This condition generally has an impact on rising sea waves, especially at night. Nevertheless, according to the agency, the tidal waves would not impact people living on the southern coast of Yogyakarta since the land height on the area is higher than the sea. Meanwhile, people living in the northern coast of Yogyakarta are more likely to be affected by tidal waves occurring due to the supermoon phenomenon. BMKG further stated that the wave height in the southern coast of Yogyakarta is estimated to reach 1.5 to 2.5 meters, with average wind speeds of 5-20 knots. Hence, people living there still need to be alert.

What is the writer's purpose in writing the text?