Precise rain forecasts are still a challenge, but the Hong Kong Observatory is on the ball

I refer to the letter from Mike Bentley (“Observatory’s forecast was far from reality”, October 18), regarding the Hong Kong Observatory’s weather forecast for October 10.

A cold front crossed the coast of Guangdong during the day of October 10. Locally, there were sunny intervals before the arrival of the cold front, but isolated showers set in around noon when the cold front moved closer to the territory.

Noting that showers would spread to other regions of Hong Kong and the duration of showers would vary from place to place, the Observatory updated the forecast from “a few showers” to “occasional showers” at 12.35pm to reflect the latest situation. At 1pm, “isolated thunderstorms” was added to the forecast and soon afterwards, the observatory also issued “special weather tips” to alert the public of heavier rain. Between 1pm and 2.45pm, rain was heavier over the urban areas and the southern district but was not widespread. Only two lightning strokes were detected during the period.

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Despite the advancement in science and technology, forecasting precisely the time and location of localised heavy rain remains a challenge. Nowcasting, or short-term forecasting for the next couple of hours, is an internationally recognised technique to handle such changeable weather.

Designated by the World Meteorological Organisation as a Regional Specialised Meteorological Centre for Nowcasting, the observatory will continue its sustained research and development efforts in applying state-of-the-art technologies to further enhance its weather services for the public.

Lee Lap Shun, senior scientific officer, Hong Kong Observatory