Tuesday, 18 March 2014

Couching Weather Predictions

We are barely into spring and already meteorologists are predicting Hong Kong will encounter four to seven typhoons this year.

The Observatory is couching itself with vague warnings because weather patterns have become increasingly unpredictable thanks to climate change.

Freak weather conditions like flooding in Britain, snowstorms in the eastern United States and record-setting heat waves in Australia are making it harder to accurately predict the weather, Observatory director Shun Chi-ming said yesterday.

"We can't attribute every extreme weather condition to climate change, but if you piece all of these extreme events together, we can feel that climate change is happening," Shun said. "To some extent, this will make our forecasts more challenging."

Typhoon forecasts are usually made based on the sea surface temperatures of the Pacific Ocean and are "normal", he said.

Shun explained the unusual cold winter this year was because of atmospheric "blocking" where regular air streams stagnate, causing temperatures to go above or below the normal range and have extended periods of extreme weather.

He said this was due to the close relationship to the melting of Arctic ice because of increasing sea surface temperatures.

"As climate change progresses, more extreme weather will arise," Shun said.

There are projections there will be about seven typhoons coming within 500 kilometres of Hong Kong, about the same as last year, whereas 2012 saw five that included a No. 10.

In addition it is expected there will be less rainfall this year at between 1,700mm to 2,300mm, which is considered normal to below normal.

And to cover all bases, Shun says rainfall will either be light or very heavy. "We anticipate a rise in the number of extremely wet years in the 21st century, but the likelihood of drought episodes remains."

Meteorologists believe Hong Kong's sea levels will rise 40cm by the middle of the century due to the rise in temperatures by 2 degrees Celsius.

From April, the Observatory will present a nine-day weather forecast to replace the current seven day one due to technology allowing for more accurate forecasts.

So basically have the umbrella on standby and if you don't have them yet, invest in some good rubber boots, Hong Kong's latest fashion accessory.


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