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

A storm surge

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

The whyStrong 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

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

The whyA 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

HintWhat is the difference between a flood from the ocean and a flood from a river?

The whyMost 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

HintProperty cannot be moved in time, but something else can.

The whyMost 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

HintCompare its timing and purpose with search and rescue.

The whyRescue, 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

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

The whyWeather 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

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

The whyThe 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

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

The whyA 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

HintCompare running across an open field with running through a thicket.

The whyMangroves 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

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

The whyComputer 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

HintA round figure, three above normal human body temperature.

The whyThe 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

HintTraffic lights use the same colour for 'stop'.

The whyWarnings 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

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

The whyIn 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

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

The whyWeather 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

HintThink about why washing dries faster on a hot day.

The whyFor 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.