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Friday, 1st August 2008

Watching from my hospital room

This is my third day in the hospital.

The window of my room faces north, with Tai Mo Shan in the distance and a good view of the sky above. This is an excellent post from which to observe the changing winds and clouds.

In the past two days, clouds were all moving from the left to the right. It was a reflection of the south-westerly monsoon brought to southern China by Typhoon Fung-wong which had earlier landed in Fujian. The cumulus clouds grew and dissipated incessantly. From time to time, a shower or two would pass by. I could feel the freshness of the air even sitting behind the window. It made the stuffy heat and haziness a few days back look like another world. The oceanic air coming to Hong Kong from the south-west is untouched by human smoke and fire. It brings with it the breath of Nature itself.

Today, looking through the window, the clouds have changed direction. They now move from the right to the left. Closer watching reveals that the clouds organized themselves into several "cloud streets" which run from the south-east to the north-west. Puffs of cloud move along several parallel tracks. Those crossing the Kowloon Peninsula tend to dissipate on the way. Those approaching Tai Mo Shan show much more energy and grow tall and high.

The signs are that the Pacific ridge of high pressure is extending westward to southern China and that the south-easterly winds on the edge of the ridge are displacing the south-west monsoon. Weather will become more stable, but the day-time heating inland could still trigger off isolated showers.

Apart from the gentle breeze from the sea, what people particularly like about the weather in a south-east wind regime like this one is probably the clear, pristine air. From my hospital room, the radar station on top of Tai Mo Shan looks as if it were just a few feet away. The air from the Pacific is free of dust and appears virtually transparent.

7:15 p.m. - a big red balloon is released by the King's Park Meteorological Station, a short distance to my north-west. It rises quickly, flying towards Tai Kok Tsui following the prevailing south-easterly winds. It soon disappears into the dimming twilight. The package of instruments which it carries measure air temperature, humidity, air pressure, wind speed and direction. Soon afterwards, colleagues at the observatory headquarters will know how it looks like above Hong Kong. Together with weather information from the region, they could then predict the weather for tomorrow.

In my hospital room, I don't have all the information. But I could imagine the south-easterly winds at the edge of the Pacific ridge engaging with the south-west monsoon which has not retreated very far. This conflict could eventually lead to the formation of low-pressure areas in the northern part of the South China Sea near Hong Kong.

The opening of the Olympic Games is getting close. Observatory colleagues have already started taking weather observation at the equestrian venue at Shatin for a week. Thinking about the event is becoming a preoccupation. Would the low-pressure areas bring high winds and heavy rain? Or would it instead bring the perfect weather for the equestrian event, with a mostly cloudy sky but little more than a brief shower or two? No matter what happens, one thing is sure. We shall be keeping a close watch all the time.

C.Y. Lam

Last revision date: <17 Jan 2013>