Rain's Wrath Aided By Folly.

"The weather is an incredibly complex system subject to infinite variables that change rapidly. Hence, making short-term forecasts is extremely tricky."

A week is a long time in politics. The government received praise for timely warnings and preparations as Super Typhoon Saola barreled towards us. Noting the typhoon could severely damage the city, the warning signals went up early. The emergency services stood ready as a constant stream of announcements came forth, while a 'home-team' press conference presented a well-coordinated effort. 

As the typhoon ran south of Hong Kong, the violent winds brought down trees, a few hoardings collapsed, and windows broke. But, the impact was minimal — partly because of the shutdown, with most folks sheltering at home.

Then, a week later came the tail end of Typhoon Haikui, which unexpectedly dumped vast amounts of rain in hours. Between 11 p.m. and midnight on Thursday, 7 September, the Observatory recorded 158 mm of rainfall (6.2 inches). Over 24 hours, the recorded rainfall was roughly equal to a quarter of the city's annual average - breaking all records.

Hong Kong is well prepared for tropical downpours, with drainage gullies crisscrossing the hillsides and feeding away water into reservoirs or the sea. In recent decades, we invested vast sums in new underground tunnels, without which the outcome could be worse. 

In the aftermath of the rain storm, the inevitable comparisons began. Why had Hong Kong handled the typhoon well, yet the forecasts for the rainstorm came late and didn't do it justice? 

For starters, the two events were different. Monitoring large typhoons is pretty straightforward, but predicting localised rainfall is far more challenging. 

On the weather radar, it was possible to see the rainfall patterns. We'd be spared if the clouds burst a matter of 20 km to the east. If the Observatory is over-cautious, criticisms come, and if the weather behaves in a way they didn't predict, they again catch the flak.

Meteorologists use computer weather models to make forecasts, and Hong Kong has one of the most advanced systems powered by a Cray supercomputer. And since we can't collect data from the future, models have to use estimates and assumptions to predict future patterns.
 
Moreover, the weather is an incredibly complex system subject to infinite variables that change rapidly. Hence, making short-term forecasts is exceptionally tricky.

Further, climate scientists tell us that a one-degree increase in the atmosphere's temperature increases the moisture-carrying capacity by seven per cent. In turn, this means more rainfall. We know the atmosphere is warming (let's not argue the causes here), so increased rain may be expected. 

The current prediction models may need tweaking. Likewise, the government should use the 'emergency alert system' for black rainstorm warnings because many folks complained of not being aware the weather was deteriorating. A simple EAS message should address that issue. 
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As regards the ability of the city to handle such large amounts of rainfall, we must do more to avoid landslips, blocked roads, flooded tunnels, and the MTR out of action. 

And yet, the actual bullet we dodged was a possible catastrophic tide surge heading up the Tolo Channel to take out Shatin and Tai Po. I've written about the events of 1 September 1937. Estimates of the number killed vary from 10,000 to 12,000 as a tidal surge swept through Shatin. This surge was not the first. Similar events occurred in 1874, 1906 and 1923. In 1937, the public laid the blame on the Observatory. Sounds familiar. 

Today, the area is home to millions. Atop that, the narrowing of the Shing Mun River will likely enhance any surge effects. Besides a mass evacuation, the only sensible solution to a possible surge is a barrier across the Tolo Channel. At its narrow point, the channel is about 1.5 km wide. Something akin to the Thames Barrier should be technically workable and may be necessary as sea levels rise. 

Meanwhile, a distracted public is captivated by events at the luxury Red Hill development. A slope collapsed, exposing three houses to scrutiny for illegal structures and occupying government land. A civic group now suggests that 173 'millionaire row' villas have problems. Seeing rich folks squirm appeals to the sentiment that the wealthy get away with too many things in this town. 

The searching eye now extends to the nearby exclusive Villa Rosa development. No doubt we will hear more about broken laws.

That the agencies responsible didn't tackle these issues raises many questions, not least because it comes up repeatedly. Is it willful blindness, a lack of commitment and resources, or an unwillingness to tackle vested interests? Either way, public safety is compromised for greed. 

It is unclear whether this latest saga will bring long-term change or another short-term spasm of activity until public interest wanes. In 2011, Carrie Lam made great fanfare that she'd tackle the illegal structures issue. That didn't happen, in part, because the problem is enormous with an estimated one in four properties having illegal structures. 

Only a long-term, sustained effort will make inroads to ensure public safety. A starting point would be to mandate property sales are accompanied by certification that no illegal structures are on the site.

Plus, I trust someone is looking at the tidal surge issue and considering that threat. Next time, we may not be so lucky.