More wet weather on the way – updated 19.17 (6/7/12)

As predicted the heaviest rain has headed further south and the midlands have recieved the brunt of the rain today, with many, many places reporting flooding, including Yorkshire and Durham, while the South West is expecting upto 100mm of rain tonight.  There is still heavy rain forecast in the region tonight and looking at the radar it looks like from around 8′o clock this evening could bring quite a bit of rain, and also into tomorrow but it shouldn’t cause as much disruption as originally expected.

Recent model runs have shown a slight shift in track, and the storm has shown to move slightly further south than first anticipated.  Therefore although Friday is still forecast to be very wet in the region, and it is now Saturday that looks to carry the most rainfall for us.  An Amber warning is in force for South Tyneside on Saturday, with flooding a possibility.  Tomorrow (Friday) is still forecast to be wet with some heavy downpours, and as the cold air meets warm there is a good chance of thunderstorms.  Advisories from my original post on this still stand, but attention is shifted slightly more towards Saturday now. 

With last Thursday’s events still very fresh in everybody’s minds I am sure the last thing people want to hear is that there is a lot of rain on the way, but unfortunately that is the case.  An area of low pressure sitting over the continent currently has our names right on it, and is expected to hit the UK, more specifically North East England, on Friday.  Accordingly the Met Office have weather warnings out relating to this weather system, and the North East currently has an Amber warning for some regions, and a Yellow warning for other areas.  These warnings are in response to the massive amounts of rainfall forecast.  Thursday is forecast to be wet/thundery with the potential for some locally heavy outbursts, especially in the afternoon, but it is Friday and Saturday that everyone has their eyes on.  Following recent heavy rainfall many areas are already saturated, and with the possibility for 60-100mm of rain on Friday that could cause problems with flooding, not only surface flooding, like we saw on the 28th June, but areas within the Amber warning area could also see some rivers overflow  Driving conditions could potentially be hazardous, and disruption to travel is likely, especially given that some services are still not running a normal route due to the recent flooding problems.    Looking ahead to Saturday, the area is still under an Amber alert from the Met Office, with further heavy and persistent rain forecast.  Again there is a likelihood of flooding from both surface water and rivers, and disruption to travel is likely.  With any weather event there is always uncertainty over where exactly will get the most rain, currently there is a high chance that the North East is in line for a very disruptive few days, and people should be aware that large amounts of rainfall are forecast and take appropriate action.  This page will be updated as more information becomes available, tomorrow’s 24 hour forecast will be more reliable than what is currently available and will shed more light on the exact track of this system.

For information on flooding and/or flood alerts please see the environment agency:

http://www.environment-agency.gov.uk/homeandleisure/floods/default.aspx

What is causing this unseasonal wet weather?

Many people are left scratching their heads at the rather extreme weather we have been experiencing of late, and as is often the case this is down to the jet stream.

The jet stream is a much talked about thing, but not many people actually know what it is, or what it does.  A jet stream forms high in the upper troposphere between two air masses of very different temperature. The greater the temperature difference between the air masses, the faster the wind blows in the jet stream.

This river of air has wind speeds which often exceed 100 mph, and sometimes peak over 200 mph. Jet streams usually form in the winter, when there is a greater contrast in temperature between cold continental air masses and warm oceanic air masses.  During the winter months, Arctic and tropical air masses create a stronger surface temperature contrast resulting in a strong jet stream. However, during the summer months, when the surface temperature variation is less dramatic, the winds of the jet are weaker. In summer, if the jet stream is to the north of us, we would generally have a warmer, drier summer, whereas if the jet stream is to the south of us, summers are usually wetter and cooler.In winter, a more southerly jet stream leaves us open to cold conditions to the north and east. Normally the jet stream in winter ensures generally mild, and at times wet and windy weather across our shores.

The jet stream is powered by temperature contrasts between the cold polar regions of the planet and the hot tropics. The heat wave that America is experiencing has pushed the jet stream further north than you would expect, and this has caused a large area of high pressure to form over Greenland, which has then pushed a part of the jet stream over the UK.

As it should be

For for the last three months, we have been under an accelerating part of the jet stream which has caused this horrendous wet weather we have had.  The jet stream is currently sitting to the south of the UK, which is drawing in these low pressure systems, which in turn are merging with the hot humid air from the Continent, and that is what is causing this torrential rain and thunderstorms we have been experiencing.

Current jet stream - this pic is from 2007 but we have a similar set up at present

The bad news is there is no change in forecast for at least 2 weeks, which means July has as much chance to be record breaking as June and April have been rainwise

Pictures courtesy of the BBC.

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