April 25 2014 Latest news:
Monday, December 23, 2013
It was a textbook case of a perfect storm – although perfect is not the word anyone affected by this month’s tidal surge would use.
A rare line-up of tide and wind and weather system conspired to drive a surge of seawater from the Atlantic, around the top of Scotland and down to smash into the cliffs and homes of Walcott and swirl through the streets and into front rooms and businesses around our East Anglian coast.
The tides were predicted years ahead, the weather system picked up several days before the floods – but, said weatherman Jim Bacon, it was only at the previous high tide, just 12 hours beforehand, that a possibility became a probability and then a full-scale emergency.
Today every episode of extreme weather is examined for clues that it might be due to climate change but Jim said this month’s storm and tidal surge cannot yet be used as evidence – and might never be.
“There is a feeling that the climate change scenario would lead to an increase in the number of storms coming across the Atlantic, but we are talking about long-term,” said Jim. “There is no way of saying that an individual storm was anything to do with climate change.”
He said it could be decades before scientists will be able to determine a trend.
Right now there is some evidence that winter storms might become more frequent – but for a storm to lead to storm-surge flooding a whole series of factors have to line up including:
• A low pressure system moving north of Britain on exactly the right trajectory to send strong northerly winds down the North Sea and push Atlantic water round the top of the Scotland and down the narrowing funnel of coastline between Norfolk and Holland.
• The particularly high tides that occur twice a month, just after the new and full moon, (somewhat confusingly known as spring tides) when the sun, moon and earth line up and the gravitational pull on water of the oceans is greatest.
• The strength of the wind is exactly in phase with the tide.
• A previous high tide is prevented from ebbing away by the wind.
If all these meteorological and astronomical factors swing into view on the computer models and charts, and on the real-time measurements from satellites and weather stations, then emergency plans from sandbags to evacuation, are the next line of defence against disaster.
Sixty years ago people had no warning of the terrible storm surge which killed 100 people in Norfolk alone. Today the dangers can be predicted and communicated.
“Things are so much better understood from the scientific side but also the public is so much better informed. All of that makes it less likely that there will be an extreme loss of life,” said Jim.
Right now, with a succession of storms sweeping across the country, forecasters are able to predict where and when the rain will fall and the wind will blow with increasing accuracy. They might even be coming to the conclusion that there could be more of these storms in the future.
What they cannot yet say is that these will lead to more storm surges along the Norfolk coast because although the tides are fixed, the paths of weather systems are not.
Instead, forecasters watch for the next coming together of tide and wind and dangerously deep winter low pressure systems over the Atlantic.
“And there will be a next time,” said Jim. “And there is no rule in the rule book that says you can’t get one that is just a bit deeper.”
If you are dreaming of a white Christmas – go north as Norfolk is heading for a windy Christmas instead. Weatherman Jim Bacon said: “There is a lot of cold air about. I think some places in the north will have a white Christmas but it’s going to be blowing a bit of a hoolie down here! Santa won’t need his spinnaker up!”