Is there a UK ‘heatwave’ on the way?

25 03 2013

There have been some headlines today suggesting the Met Office has forecast a ‘heatwave’ by the end of spring.

The articles reference a line from our March to May three-month outlook for contingency planners which refers to how our Spring weather can change depending on where large areas of ‘blocking’ high pressure systems lie in relation to the UK – something we recently wrote about when contrasting the weather this March to that of last year.

This is not, however, a forecast of what the weather is expected to be like at the end of the spring or whether a ‘heatwave’ is likely or not, but is an indication of how average temperatures may differ from normal throughout the whole three month period of March, April and May.

Clearly this is the time of year when temperatures rise in response to the sun getting higher in the northern hemisphere sky, the days get longer and continental Europe warms up. So we will undoubtedly get some warmer spells of weather as the months go on and these will be picked up in our accurate five-day forecasts, as well as our forecasts out to 30 days ahead, which gives a more general view of the weather ahead over a longer-timescale. It is our accurate five-day forecasts and weather warnings provide the best possible advice and detail on what weather to expect in the UK.

This week is set to remain very cold with further wintry flurries in places.





Why is it so warm?

26 03 2012

The last few days have been unseasonably warm but why is this happening so early in the year? The answer lies largely in the air flow directly above the United Kingdom but more importantly where that air has come from.

Over the last week or so we have been under the influence of high pressure which has given us very settled conditions, with light winds and a lot of sunshine. During the daytime, the sun has injected plenty of warmth and the light south to south-easterly winds have drawn further warm air towards us from continental Europe.

UK visible satellite image from 0900 GMT 26 March 2012. Source: Met Office/EUMETSAT

We would normally expect average maximum temperatures in March to edge into double figures across the south of the country and stay much cooler further north. However, over the last few days temperatures have reached the low twenties and we have seen a new record high for Scotland in March as the temperature reached 22.8 °C at Fyvie Castle in Aberdeenshire on Sunday 25 March and temperatures are expected to reach similar values over the next couple of days.

The last time we had a comparable warm spell in March was during 2005 between the 16th and 26th when temperatures reached 21.8 °C at Kew Gardens on the 19th. Before that we have to go back to 1968 and 1965 when two shorter spells (which coincidentally both happened for the same two-day period in March, from 29th to 30th) saw highs of 25.6 °C at Mepal, Cambridgeshire and 25.0 °C in Wakefield respectively, both on the 29th.

Average maximum temperatures for March.

The settled and clear conditions by day continue during the night time and allow much of the sun’s energy to escape from the earth’s surface back into the atmosphere, allowing temperatures to fall quickly after dusk. So, in contrast to the warm, sunny days, the nights are clear and cool, especially this time of year. Although we are seeing temperatures reaching in excess of 20 °C by day, we have seen overnight minima fall below freezing in some areas and many of us are waking up to frosty mornings. With light winds, mist or fog patches are also likely to form.

The weather forecast for the next few days remains settled and warm for much of the country with temperatures in the high teens or low twenties. But later in the week, the area of high pressure will drift to the west of the UK and allow a northerly wind to bring in more cloud and cooler air to all parts, with the chance of a few showers.

 





Blog about fog: why has fog been so persistent this week?

15 03 2012

Foggy weather has been especially persistent this week, not clearing all day in some areas of the UK.

Fog forms when relatively moist and mild air close to the ground cools quickly, causing the moisture in the air to condense (at which point it becomes visible to the human eye). This normally happens in autumn and winter under clear skies, which allows heat from the ground to escape quickly to cause rapid temperature drops.

Over the last few days winds have been light with an area of high pressure sitting rather stubbornly over the UK. This creates the ideal conditions for fog to form. As the fog is so dense in places the temperature has not been warm enough to cause the fog to evaporate, such as in more western parts yesterday.  However in eastern parts both yesterday and today the sun has got to work quite quickly on the fog, either lifting it into low cloud or breaking holes in it and eventually clearing it completely.

The fog is expected to clear today, with more changable weather on the way over the next few days. Keep up to date with your local forecast for the latest.

If you want to find out more about fog, have a look at our fog blog, ‘what is fog?‘ or our water in the atmosphere factsheet.








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