Is a heatwave on its way?

Thursday 17th Jul 2014 by theWeather Club

There have been lots of reports in the media and warnings from meteorological service providers about a heatwave occurring across parts of England over the next couple of days, as hot and humid air is drawn up from Spain. 

The Met Office have issued a Level 2 alert from 0800 on Friday 18 July to 0800 on Sunday 20 July, indicating there is 60% chance of a heatwave for parts of England, with humid conditions leading to an outbreak of heavy thunderstorms.

The definition of a heatwave does differ across the World. The World Meteorological Organisation (WMO) broadly defines it as when the daily maximum temperature exceeds the (1961-1990) average maximum temperature by at least 5oC for five or more consecutive days. In the UK, the precise thresholds for a heatwave vary across the country, but are typically daily maximum air temperatures above 30oC and night time values above 15oC. Weather forecasts are used to provide a ‘heat-health alert level’ (ranging from 1 to 4) for each local authority region. 

More information about the alerts is available on the Met Office website.

These hot and humid conditions can be traced all the way back to Super Typhoon Neoguri which occurred in the Northwest Pacific in the first week of July. Neoguri altered the Jet Stream by drawing up a mass of warm tropical air and set in motion a wave of extreme weather across the globe. This brought contrasting temperatures to the east and west of North America and is allowing a ‘Spanish plume’ to reach the UK over the next couple of days.

A video explaining the causes can be found on the BBC website

During heatwave conditions it is important to take steps to cool down whenever possible by keeping curtains and blinds closed, opening windows particularly at night time, turning off non-essential electrical items which generate additional heat, drinking plenty of water and not overexerting yourself. It is particularly important that vulnerable people such as the elderly, young children and anyone who is unwell take extra care and where possible, check up on those who may fall into this category. And remember your sunscreen and sunglasses if you're outdside in the sun!