Thunderstorms bring intense rainfall to parts of England

28 07 2014

This morning has seen some intense downpours across parts of south east England.

They developed across parts of East Anglia in the early hours of the morning, with further areas of heavy showers across Sussex, Surrey, Kent and the south of London following later.

The showers were very heavy in places with thunderstorms, hail, and torrential rain reported, giving high rainfall totals and localised flooding in some areas.

The high rainfall totals were caused by an area of low pressure and a plume of warm air that moved in from the near continent accompanied by light winds, meaning that the showers were slow moving.

Several spots have seen more than half of their average monthly rainfall for the whole of July in just one hour.

Below you can see some of the highest recorded hourly rainfall totals from Environment Agency rain gauges through the morning of Monday 28th July 2014:

Great Dunmow Essex 43 mm (4am to 5am)
Isfield Sussex 37 mm (8.30am to 9:30am)
Ardingly Sussex 35 mm (8.30am to 9:30am)
Santon Downham Suffolk 33mm (4am to 5am)
Weirwood Sussex 28 mm (9am to 10am)
Northolt London 20mm (7am to 8am)

 

The band of showery rain is now easing, but a yellow warning for rainfall remains in place for the south east of the UK as the risk of seeing some further isolated downpours remains.

In addition, the far south east of England could see further persistent and perhaps locally heavy rain later today and overnight, with parts of Kent and Sussex most at risk. Conditions across all areas should then improve through tomorrow.





Rain totals for 19th July 2014

20 07 2014

As forecast there were severe thunderstorms across the UK on the 19th July bringing heavy rain and gusty winds. See the tables below for the largest rain totals across the UK.  Gloucestershire recorded the highest rainfall with 66mm between 6am and 6pm yesterday, the counties monthly average rainfall is 60.6mm.

The Heat-health watch put in place in parts of southern and eastern England in conjunction with Public Health England has now been downgraded. Temperatures in parts of the area covered topped 28C during 19 July, see table below.

Today, 20 July, temperatures are expected to reach low to mid 20’s across central, south and south east of England, with London seeing around 27C.  Northern England will reach mid to high teens and Scotland and Northern Ireland mid to low teens.

More thundery downpours are expected to develop today over some eastern and central parts of the UK.  A yellow, be aware, weather warning for rain is in place for the areas likely to be affected. Not everywhere will see a storm but where they do occur, torrential downpours are possible with lightning, hail and strong gusts of wind. The areas most likely to be affected are across eastern and southeastern England.

Many places will have a good deal of fine and very warm weather this working week although there is the risk of some heavy showers in parts of the south and west later in the week.

 

UK MAX TEMPERATURE 19 JULY 2014
TIME SITE NAME AREA MAX TEMP (Celsius)
16:22 London St Jamess Park GREATER LONDON 28.5
15:13 Northolt GREATER LONDON 28.4
15:22 Heathrow GREATER LONDON 28.3
15:59 Santon Downham SUFFOLK 28.3
13:29 Gravesend, Broadness KENT 28.1
16:51 Cambridge NIAB CAMBRIDGESHIRE 27.7
15:49 Marham NORFOLK 27.7
13:55 Hampton W Wks GREATER LONDON 27.6
16:52 Writtle ESSEX 27.6
14:51 Frittenden KENT 27.5

 

 

12hr UK RAINFALL 19 JULY
SITE NAME AREA PRECIP. (MM)
WESTONBIRT GLOUCESTERSHIRE 66.0
PERSHORE COLLEGE HEREFORD & WORCESTER 36.4
PERSHORE HEREFORD & WORCESTER 30.8
NEWPORT (SALOP) SHROPSHIRE 29.4
KEELE STAFFORDSHIRE 28.2
ASTWOOD BANK HEREFORD & WORCESTER 27.6
NOTTINGHAM, WATNALL NOTTINGHAMSHIRE 26.0
LIBANUS POWYS 25.8
NANTWICH, REASEHEATH HALL CHESHIRE 22.6
MARKET BOSWORTH, BOSWORTH PARK LEICESTERSHIRE 22.6




With hot and humid weather could we see a ‘Spanish Plume’?

15 07 2014

Over the next few days increasingly warm and humid air moving up from the continent will see UK temperatures on the rise, with the warmest days of the year so far expected.

Temperatures in the south east of the country could climb to the low 30s Celsius by Friday, while other parts of England and Wales are likely to see temperatures in the mid to high 20s.

These very warm conditions will be accompanied by a close and humid feel in the air, which could make it feel quite uncomfortably warm in places – particularly during the nights.

While there is a good deal of dry and fine weather in the next few days, there is also the chance of seeing some heavy rain and thunderstorms as we go into the weekend.

Friday may see an area of thundery showers moving north east across parts of England and Wales.

Our meteorologists are also keeping a very close eye on the potential for more widespread thundery downpours on Saturday.

These could develop from what meteorologists call a ‘Spanish Plume’, which is a catchy name for a rather complex set of conditions.

It involves very warm and humid air moving up from the Spanish plateau to the UK. If this meets cooler air from the Atlantic, the warm air can be forced rapidly upwards to produce thunderstorms.

There are a number of ingredients that all have to come in to place for this to happen, however, so the risk of disruption from any heavy, thundery downpours is low for Saturday at the moment rather than a certainty. A yellow alert has been issued for this risk and will be updated in the coming days.

You can keep up to date with how this situation develops by checking our forecasts and warnings over the next few days.

Interestingly, the warm weather we’re expecting can be traced back to the jet stream, a narrow band of fast moving winds high up in the atmosphere which forms where cooler air from the polar region meets warmer air from the tropics.

The jet stream has dipped south over north eastern parts of the US, allowing cooler air to flood in over the area and bringing much lower temperatures than usual for this time of year.

New chart v1

Top image shows forecast jet stream at 1am Wednesday, with an obvious kink over the NE of the US. The bottom forecast image, for 1am on Saturday, shows a kink now over Spain, with warm air from that region flowing towards the UK.

This kink in the jet stream causes a knock-on effect which pushes the cooler air south across the Atlantic, which in turn pushes the warm humid air over the continent (around Spain) towards the UK later this week.

This provides yet further proof of the way in which all weather is connected, but there are no hard and fast rules as to how events in one part of the world will affect us here in the UK.





Five things you might not know about thunderstorms

20 03 2013

1. Lighting can strike twice. The empire state building in New York has been struck by lightning as many as 48 times in one day.
2. The average flash of lightning would light a 100 watt light bulb for three months.
3. Lightning can strike in volcanic ash clouds. Not much is known about volcanic lightning, but we’re using it to help track ash clouds.

Volcanic lightning

Volcanic lightning

4. Thunderstorms can trigger asthma. The Met Office has worked with the NHS and Asthma UK to try and understand why.
5. The most thundery part of the earth is the island of Java where the annual frequency of thunderstorms is about 220 days per year.





Top ten: spookiest weather conditions

30 10 2012

As it’s halloween  tomorrow, we’ve taken a look at the top ten spookiest weather conditions. From well known scary weather – like thunder and lightning and sea mist, to lesser-known phenomena such as brocken spectre and fall streak holes.

  1. Fall streak hole. Also known as a hole punch cloud, these clouds sometimes cause people to think the world is ending, especially when wispy vigra clouds are descending from the hole. The exact conditions that cause them to occur are still debated.
  2. Sea mist. This occurs when mild air moves over the sea, which is cooler. It can be particularly spooky when sea mist comes in during the day and visibility is drastically reduced.
  3. Sunsets. Although often considered beautiful, some particularly vibrant red sunsets can create a spooky effect.
  4. Dust storms. Dust and sand storms can be whipped up rapidly by strong winds in arid regions. Dust storms can look particularly ominous as they approach as they can be up to 40 metres high.
  5. Whistling wind. Windy conditions can be scary when they blow through objects causing a whistling sound.
  6. Brocken spectre. This effect is produced when an observer stands above the upper surface of a cloud – on a mountain or high ground – with the sun behind them. When they view their shadow the light is reflected back in such a way that a spooky circular ‘glory’ appears around the point directly opposite the sun.
  7. Roll clouds. These ominous looking clouds are a type of arcus cloud usually associated with a thunderstorm or a cold front. As these rare clouds often appear to be ‘rolling’ they often cause fear that severe weather is on the way.
  8. Thunder and lightning. One of the most common forms of ‘scary weather’, thousands of thunderstorms are taking place at any one time across the globe.  The lightning you see during a thunderstorm is a large electrical spark caused by electrons moving from one place to another, while the rumble of thunder is caused by the noise of intense heating and expansion of the air along the path of the lightning.
  9. Clouds over a full moon. This spooky effect occurs when clouds partially cover a full moon.
  10. Fog. 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.

What weather conditions do you find the spookiest?





Severe weather expected in parts of Spain and southern France

19 10 2012

This weekend looks set to be a very wet one over parts of Spain and southern France as very warm, humid air and an active weather front combine to bring heavy rain and thunderstorms.

The frontal system stretches from Scandinavia, across southeastern Britain to North Africa and it’s on the southern side of this that we are likely to see torrential, thundery downpours bringing the risk of flash flooding.

Visible satellite image 3.30pm 19 October 2012

Southeastern Spain, from Murcia to Valencia and Cuenca, may see some of the heaviest rain on Saturday, but it’s the north and east of Spain and parts of southern France that are most at risk from the torrential downpours through the weekend. Here there could be 100 to 200 mm of rain falling in a short space of time across quite a wide area, with the risk of up to 300 mm of rain possible in places.

Some severe thunderstorms are also likely across parts of Morocco and Algeria, with gusty winds generating dust storms.





Met Office in the News: “Tropical Storms to hit Wimbledon”?

26 06 2012

There have been several articles in the Daily Express over the last couple of days reporting ‘Summer is on the way at last’ with temperatures set to reach 34 Celsius this week and ‘Tropical storms set for Wimbledon’.

These headlines are unfortunately wide of the mark and rather misleading, both by implying that hot and sunny weather is on the way and that Wimbledon will be hit by tropical storms.

Although the Met Office has spoken to the Daily Express, the forecasts featured in the stories have not come from the Met Office, but from an independent forecaster.

The Met Office forecast for this week is for a couple of days of warm, humid and rather cloudy weather across much of the UK, with temperatures reaching 26 or 27 Celsius in any sunshine. For more detail you can find the latest weather forecast on our website.

It is our understanding that the temperatures of 34 deg C referenced in the articles are actually feels like temperatures taken from the website of an independent forecaster rather than actual air temperature. This is not made clear within the article and is potentially misleading.

The inference – through the lack of reference to the original source of the forecasts – that these forecasts have come from the Met Office is very misleading for the public, and potentially damages the reputation not only of the Met Office, but the wider weather forecasting community.

The Met Office is a world leader in meteorological science and our forecasts are recognised the world over as some of the best in the world. We are proud to be trusted to give the best possible guidance on the weather by the public and we report the weather exactly as it is.








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