Thunderstorms (From Worcester News)

Thunderstorms

12:05pm Monday 22nd June 2009

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Thunderstorms occur within unstable air especially during the warmer summer months. Huge bubbles of moist warm air ascends, the water vapour condenses. This releases latent heat which helps to maintain the warmth of the air, so the air continues to rise until towering storm clouds (cumulonimbus) with those vivid white anvil shaped tops appear, which is an indication that torrential rain, accompanied by hail, thunder and squally winds are about.

Storm clouds can be formed by ground heating, also by converging air, triggering the lifting of surface air, storms can also be produced by air lifting over high ground such as hill and mountain ranges. More violent storms occur ahead of cold fronts, especially when the weather has been very warm or hot, when winds converge over a broad zone.

Thunderstorms can also be triggered over large Towns or Cities where extra heat fuels those thunder heads. Some storms produce so much rain that the drainage system and sewers are overwhelmed, which forces heavy sewer tops to be lifted, causing flash flooding often away from any river source. As global warming accelerates these heavy cloudbursts will become more frequent and troublesome

Inside a thunder head warm air rises rapidly, cools at the top of the cloud, starts to sink, warms as it sinks, then rises again. This forms convective cells.

Next Week: Lightning.

Glossary: Latent Heat: The heat energy that must be absorbed when a substance changes from solid to liquid and liquid to gas, and which is released when a gas condenses and a liquid solidifies.

Weather for coming week Monday 22nd June-Friday 26th June

High pressure influencing our weather during this period bringing a cloudy start to the week, then increasing amounts of sunshine and higher temperatures as the week moves on. Light east to north-east airflow. Humid nights with some dawn time mist.

Maximum temperature 23-26c 73-79f.
Minimum temperature 13-15c 55-59f.

Last Week's Observations ( Monday-Sunday)

Highest day temperature...........22.9c on Monday 15th June.

Lowest night temperature.........7.9c on Wednesday 17th June.

Wettest day............................3.5 mm on Monday 15th June.

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