We saw as much as a months worth of rain fall within just 3 hours yesterday over parts of West Yorkshire and the heavy, torrential and slow moving rain clouds continue to bear down on central and eastern parts of England and Scotland at the moment. There is continuing concern for northeast England up into the Lothians and Borders region of Scotland this evening and overnight, including the city of Edinburgh as the stalled front responsible for the big rains goes nowhere, we could see rains turn even heavier. All this comes following a soaker of a weekend across the same area where parts of Edinburgh were under water including the famous Princess Street Gardens which sits beneath Edinburgh Castle.

Just when you thought we couldn’t see anymore rains following April and June right, wet get hit by what appears even MORE rain during the first 10 days of July. I think there is a distinct possibility we could quite easily see our wettest July on record also, we’re well on track and given what the models are showing, there is plenty more rain in store for us over the next 10 days.

Next 10 Days offers continued wet for next 5, brief respite with sunshine and warmth early next week but big rains return mid next week onwards

The ECMWF clearly shows more widespread heavy rains over the next 5 days which will keep the flood situation going strong. The soils over parts of eastern Scotland and many parts of England/Wales cannot hold much more water and so we’re likely to see enhanced flooding in already flooded areas as well as flooding in areas which have been largely unaffected so far.

The hose looks to stay on through Saturday and probably Sunday before we start to see surface as well as upper level ridging build in from the west. This trough sliding east will allow this ridge to work in but a boundary lies over Scotland and so heavy rains spread over the Highlands which interestingly isn’t a bad thing given their rain deficit.

28C for Midlands & South early next week?

This set up of low and upper ridging could pump a decent surge of heat out of the Azores on Monday, peaking probably Tuesday and then easing Wednesday but staying fairly warm. We could well see temps climb towards the 27 or 28C over parts of the Midlands and South early next week. As long as the atmosphere is capped, we shouldn’t see wet weather but if there’s a break in the cap, perhaps due to the wet soils adding lift by increasing humidity which can ignite thunderstorms, it should be a fine first 3 days to next week.

The northern half of the UK remains wet though likely warmer too. I could see low 20s across southern and central Scotland as well as mid-20s across southern Ireland where it too should be drier beneath the high.

By Wednesday, the ridge axis pushes out into the North Sea and the next low comes acalling by Thursday. More heavy rains sweep in via the cold front and this will impact ALL areas of the UK. While southern and central areas enjoy warmer, drier weather Monday, Tuesday and possibly Wednesday, this will come to an abrupt, possibly thundery end come Thursday and the rest of next week looks to end similar to what this week will.

Why all this crazy weather?

Unfortunately the unusually strong and far south jet stream remains anchored and so all the energy continues to pile into the mean trough firmly anchored over the Western side of Europe. In response, we also continue to see unusual warmth get pumped from south-central Europe all the way up into NW Russia. According to the latest model runs, we will continue to see yet more heavy and persistent rains in clumps over the UK through the remainder of July with brief interludes between wet systems.

The trouble is that given this stuck pattern which really kicked in at the start of April and hot on the heels of the 5th warmest, 3rd driest March on record for the UK, it never really left once it arrived If you look at the NAO trend, we went negative and like back last winter, it remained in the phase, reluctant to go negative during winter which kept us mild with troughiness in the North Atlantic, ridging over the UK. Now it’s the opposite, we can’t get the NAO to go positive keeping ridging to our west and the trough locked between the high to the west and to our east. One could argue that this trough and it’s unsettled pulses of weather have intensified as we went from sprin into summer, bringing more intense rains.

Yes, rainfall has increased and when you push the jet further south than it should be, it intensifies as it draws down cooler air into a dominantly warm environment. Push cool into and over warm and you’ve got big rains developing. Waters surrounding the UK as well as the air have warmed with the season and as cold pools swing through with energy via the low pressure system, this forces heavy rains. A likely factor which has enhanced these rains has been the abnormal warmth dominating Spain as low’s have approached the UK. Southwest winds force hot air and humidity from Spain north, into the low which is over the UK, this produces tremendous amounts of rain but the big issue has been the slow forward movement of these lows due to the wall of high pressure to the east. This ridge has deepened the trough and slowed or stalled these lows which keeps the heavy rains going for prolonged periods of time.

Persistent high-latitude blocking can be blamed for this persistently wet, gloomy pattern, We saw this over the past 3 winters with prolonged cold spells from 2009 through 2010 then the warmth of last winter

For persistency in this pattern I blame the blocking and long duration negative or positive phases. We saw a dominantly positive NAO last winter which kept us warm. Last winters warmth may have been helped by the drought back last summer and of course this dominos from back to back, prodominantly negative NAO’s which kept us cold but more importantly, DRY! Remember dry soils can help support stronger than normal heights aloft and we did see dominant ridging dominant from the Azores to Outer Hebrides last winter.

In my opinion, it’s simple. this stubborn pattern can be blamed on persistent ‘blocking’ over Greenland. Why it holds positive or negative for as long as it does, I don’t know. An outside culprit which may have flipped the 2-3 trend on it’s head may well be the transition to an El Nino. Warming of the equatorial Pacific causes a reaction in weather patterns throughout the world. The back to back La Ninas are likely to blame for the drought in the UK but the reversal, certainly in part could be blamed I think on the El Nino and the cold PDO (Pacific Decadal Oscillation).

This current NAO setup is exactly the same as what brought us the long duration cold spells during winters 2009-10 and 2010-2011, the strongly negative NAO (North Atlantic Oscillation) was stubborn and so to is it now. Both this and the el nino is the most plausible reason behind these rains along with other factors including unseasonable warmth over Spain feeding north and the warm pool of water over the North Atlantic which is also likely adding moisture and energy into lows.

Tags: england flooding, record rains, summer 2012, uk floods 2012