Weather and climate, Year 10: tropical storm effects and extreme weather in the UK

A storm surge

提示Two words. The second also describes a sudden rush of electrical power.

为什么Strong winds blowing towards the land pile sea water up against the coast. The low air pressure at the storm's centre lets the sea rise a little more. If this arrives at high tide, water can reach several metres above normal and sweep far inland.

It saturates the soil, making the slope heavy and unstable

提示Think of what happens to a sandcastle when you pour too much water on it.

为什么A tropical storm can drop hundreds of millimetres of rain in a day. Water fills the spaces in the soil, adds weight and weakens the grip between particles. On a steep slope the soil then gives way. The landslide is a secondary effect of the storm.

The sea water leaves salt in the soil

提示What is the difference between a flood from the ocean and a flood from a river?

为什么Most crops cannot grow in salty soil, and it can take several seasons of rain to wash the salt out. Wells and ponds used for drinking water are contaminated in the same way. This is a secondary effect on both people and the environment.

Evacuate people inland or to shelters before it arrives

提示Property cannot be moved in time, but something else can.

为什么Most deaths in tropical storms are caused by water, above all the storm surge. Moving people out of the surge zone before landfall removes them from the danger. It depends on accurate forecasts, clear warnings and routes or shelters that people can reach.

A long-term response

提示Compare its timing and purpose with search and rescue.

为什么Rescue, emergency food, clean water and shelter come in the first hours and days. Work that restores normal life and reduces the damage from the next storm takes months or years. For your own named storm, be ready to give examples of each kind.

With satellite images

提示The view has to come from above, and from a very long way up.

为什么Weather satellites photograph the cloud pattern many times an hour, showing where the storm is and how well formed its eye is. Specially equipped aircraft are also flown through storms to measure wind speed and pressure directly.

The forecast is less certain the further ahead it looks

提示Would you be surer about tomorrow's weather or next week's?

为什么The cone shows the area the centre of the storm is likely to pass through. It is narrow for the next few hours and wide for several days ahead. Everyone inside it needs to prepare, not only those on the centre line.

To keep people above the floodwater of the storm surge

提示Think about which part of the danger arrives from the sea, not from the sky.

为什么A shelter must survive both violent wind and deep, fast-moving water. Strong concrete walls deal with the wind. Raising the floor several metres lets the surge pass underneath. Many shelters are used as schools or community halls between storms.

Their dense roots and trunks absorb the energy of waves and surge

提示Compare running across an open field with running through a thicket.

为什么Mangroves grow in the zone between low and high tide. Water has to push through a tangle of roots and trunks, which slows it and lowers its height before it reaches homes and fields. This is a natural, low-cost form of protection.

landfall

提示A compound word: solid ground joined to a word for dropping down.

为什么Computer models use satellite and aircraft measurements to forecast the track several days ahead. Knowing where and when the storm will come ashore lets authorities warn and move the people most at risk, and avoid evacuating those who are not.

40

提示A round figure, three above normal human body temperature.

为什么The record is 40.3 °C, measured at Coningsby in Lincolnshire on 19 July 2022. It was the first time 40 °C had been reached in the UK. Records broken by wide margins are one piece of evidence that UK weather is becoming more extreme.

red

提示Traffic lights use the same colour for 'stop'.

为什么Warnings are yellow, amber or the top level, chosen by how bad the impacts could be and how likely they are. Since 2015 storms expected to cause serious disruption have also been given names, so that warnings are easier to follow. Warnings let people and services prepare, which reduces the risk.

depressions

提示The same word is used for a dip in the ground and for a low mood.

为什么In these systems warm and cold air meet and the warm air is forced to rise, giving thick cloud, rain and strong winds. They are steered across the UK by the jet stream, most often in autumn and winter. A run of several can cause serious river flooding.

Long-term records showing extreme events becoming more frequent or more intense

提示One point on a graph shows nothing. What do you need?

为什么Weather varies from year to year, so a single event could be chance. Met Office records going back to the nineteenth century show a trend: the hottest days are getting hotter and winters are getting wetter. A trend over decades is the evidence.

Warmer air can hold more water vapour

提示Think about why washing dries faster on a hot day.

为什么For every degree the air warms, it can carry noticeably more moisture. When that air rises and cools, more water condenses and falls in a short time. Intense bursts of rain overwhelm drains and rivers, raising the risk of flash floods.