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Regularly updated thoughts from from Brian Gaze, TWO's founder. Use the Follow @TWOweather button to keep up to date with Brian on Twitter.

Easter weather prospects UPDATE 6

Posted Wed, 16 Apr 2014 12:28:21

The Easter weather prospects aren’t looking great. Good Friday should be mostly dry in the west with the chance of drizzle or light patchy rain and cooler conditions further east.

Saturday probably beginning cold with a patchy frost in central and western areas, but cloudier skies further east holding up temperatures a little. The rest of the day not too bad with sunny spells, but again the chance of more cloud at times and perhaps some drizzle in central and eastern areas. Weather fronts flirting with Scotland and Northern Ireland could bring the thicker cloud and a risk of patchy rain here too.

By Easter Sunday things look set to go downhill with showers or longer outbreaks of rain across England and Wales looking likely. Here’s the rainfall forecast chart for Sunday afternoon from this morning’s GFS run.

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By bank holiday Monday it’s looking mixed with the risk of showers or longer outbreaks of rain possibly in most of the UK. Here’s the rainfall forecast chart for Monday afternoon from this morning’s GFS run.

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In summary the Easter period weather is probably going to be mixed with an increasing risk of showers or longer spells of rain. The rest of next week continues to look changeable and this pattern may last through the last third of April. Do keep up to date with the local place or postcode forecasts because there’s still time for the Easter weather details to change.

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Easter weather prospects UPDATE 5

The Easter weather still isn’t certain but obviously as it’s only a few days away things are becoming a little clearer. Good Friday is looking mostly dry but with the wind coming in off the North Sea it could well be cloudier and quite chilly in eastern counties. The brightest and warmest weather probably in the west.

By Saturday low pressure developing from the south may cause showery rain to start breaking out in southern regions. Temperatures about par for the course in England though possibly a little warmer in northern parts of the UK where the drier and brighter conditions may hang on.

Easter Sunday could see the showery rain becoming heavier and more widespread in southern and central regions. The rainfall forecast chart below from this morning’s GFS6z computer model run shows this with northern regions still drier.

06_129_precipratec

During Easter Monday the showery rain could push further north and west and in the south there is a chance of sunny spells developing.  Tuesday and beyond probably quite changeable with showers or more persistent rain at times the favoured outcome for the last third of April.

All in all a very mixed bag of weather and Easter may have come just a few days too late this year. Do keep up to date with the forecasts though because forecast confidence levels have generally been low recently and the details are still expected to change. The TWO 14 day discussion forecast will be updated tomorrow rather than Thursday to give you a heads up on the bank holiday period weather.

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Posted at Tue, 15 Apr 2014 15:51:04


Easter weather prospects UPDATE 4

Computer models have suggested everything but the kitchen sink as possibilities for the Easter weekend weather in recent days but are things clearer now?The good news is Good Friday looks set to be mostly dry across the UK, but there could be quite a lot of cloud drifting around so possibly not too warm. We could also see a breeze coming in off the North Sea making for dull and drizzly conditions near the East Coast. May be a day for enjoying your fish n chips rather than sitting on the beach if you’re heading in this direction.  Saturday currently looks a similar sort of day, so again mostly dry with variable cloud cover but also sunny spells.

By Sunday things potentially go downhill with low pressure moving up from the south. There is still uncertainty about the details but the general pattern has been shown by several successive computer model runs and we could see some heavy showery or more persistent rain affecting much of England and Wales on Easter Sunday. Scotland could be the place to be with drier conditions hanging on. Here’s the latest rainfall forecast chart for Sunday afternoon from the GFS6z model which was run this morning.

06_153_precipratec

By Easter Monday there are signs of the showery rain spreading further north into Scotland leaving all of the UK at risk of seeing wetter conditions at times. The air mass over the UK won’t be cold but if the cloud and rain does turn up  it probably will feel chilly.

Could things turn out better? Yes they could. In my experience this type of pattern with a breakdown in a settled spell from the south tends not to be well handled by computer models. Therefore, it’s possible things could be pushed back leaving a better Easter weekend. On balance though the likelihood is for more unsettled weather to return for the bank holiday period, but of course you knew that already!

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Posted at Mon, 14 Apr 2014 14:43:23


Easter weather prospects UPDATE 3

The weather prospects for the Easter weekend remain uncertain, but the general trend later next weeks is towards more unsettled conditions. There is a risk of heavy rain pushing up from the south during the Easter period, but it’s not definite yet.

This morning’s GFS computer model run suggested that Good Friday would be dry and warm. On Saturday it keeps much of the UK dry and warm again before rain arrives in the south late in the day. The rain then extends northwards on Easter Sunday and Monday.

Was this GFS run representative of the other 21 runs in the GEFS suite? In terms of temperature it was one of the warmer ones but the increasing risk of rainfall was  well supported, even if quite a lot of the other runs showed the rain resulting from a different set up. Here’s the GFS / GEFS 6z plot showing 850hPa temperatures (top half) and rainfall (lower half).

gefsens850london0

This morning’s ECM model run also showed it turning increasingly unsettled through the Easter weekend. In summary then the uncertainty remains but there is a risk of a washout developing through the Easter weekend. Nonetheless, it wouldn’t need things to change a lot for things to turn out warm and mostly dry. Stay tuned!

16 day forecast for London, Birmingham, Edinburgh, Cardiff, Belfast (our forecasts for Northern Ireland have recently been overhauled, info here)

 

Posted at Sat, 12 Apr 2014 16:23:03


Easter weather prospects UPDATE 2

On Monday I said it was too early to be confident about the Easter weather prospects and that’s still the case. In the last few days the computer models have shown a range of possible outcomes including wintry and very unsettled ones. Conversely this morning’s GFS6z run went for a reasonably settled and warm holiday period with high pressure close to the UK for much of the period before colder air starts moving down from the north west later on Easter Monday.

The GFS6z chart below shows upper air temperatures forecast for Easter Sunday, values are widely above +5C and in the south west about +8C. Remember this forecast is for about 1500m above sea level so down at the surface it would be a lot warmer probably close to 21C (70F) in the south if there isn’t too much cloud. Pleasantly warm!

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Is today’s warmer Easter outlook from the GFS6z a likely outcome? To gauge that lets take a look at the GEFS/GFS chart which plots all 22 runs to show how much they vary. The GFS6z run is represented by the thick green line and on the top plot it’s clearly well above the white line which shows the average of all the runs. In other words it’s one of the warmer solutions on offer during the Easter Period, so don’t place too much confidence in this outcome yet! Colder and / or wetter is still very possible.

gefsens850london0

Unfortunately then it’s still too early to make a call on whether your Easter egg hunt can take place outside this year. Things may not firm up until next week, but I’ll keep you posted.

Chart viewer

Posted at Thu, 10 Apr 2014 14:30:07


Weekend weather looking decent

The coming weekend isn’t looking like a classic but for much of the UK it could  be decent. The details will change but currently it looks as if there could be some rain in northern parts of the UK on Saturday, with the chances of staying dry increasing the further south you go. Cloud amounts are very difficult to be confident about at this range, but this morning’s GFS model run forecast chart for Saturday afternoon shows the brightest conditions in the south west. Possibly pretty good  in Devon and Cornwall if you’re heading down there.

06_105_ukcloud

 

By Sunday there are some hints of more cloud in western regions with the risk of some patchy drizzle. With high pressure almost certain to be close to the UK it won’t take much adjustment from the computer models to show better conditions, so this is something to look out for in the next few days.

On the whole temperatures not bad in the coming days across southern and central regions where 17C (63F) looks looks achievable if the cloud holds back. Cooler in northern Britain and Northern Ireland.

Things remain uncertain for the Easter weekend with a range of options still on the menu. Unfortunately the general trend at the moment is pointing towards it becoming more unsettled.

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Posted at Tue, 08 Apr 2014 13:07:56


Easter weather prospects

With Easter still almost 2 weeks away there’s still plenty of uncertainty about the weather prospects. This morning’s operational GFS6z run which goes out to 16 days ahead showed high pressure in charge of the weather for much of next week with some pretty decent conditions for much of the UK. Unfortunately it then went on to show heavy rain moving up from the south west late on Good Friday and continuing for much of the Easter weekend.

Here’s the rainfall forecast chart from the operational GFS6z run for 18:00GMT on Good Friday which shows the heavier rain still mostly to the south west of the UK but looking ominous.

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Given this it’s probably just as well it’s still much too early to be sure of this being the correct outcome. Is it possible to gauge confidence at this stage? Yes, to an extent. Basically the same computer model is run another 21 times with the starting conditions tweaked on each run to account for uncertainty in the starting conditions. This is the GEFS suite and if a good number of these runs show a similar outcome to the GFS operational run the level of confidence is higher in the solution.

This plot shows all of the 21 GEFS runs and the GFS operational run in green plotted to make a quick comparison possible.

gefsens850london0

The key things to note are:

1) The GFS operational run has a warmer upper level air mass across the country than most of the GEFS runs. This doesn’t necessarily mean it would be warmer down at the surface because…

2) The GFS operational run is wetter than most of the GEFS runs, so with all that cloud and rain around temperatures at the surface probably wouldn’t be anything special

3) During the second half of next week a big spread develops in the runs – on the upper half of the plot look at how they move apart – meaning forecast confidence in the GFS operational run solution is low

In summary the GFS operational run would bring a lot of pleasant weather in the next 10 days, but the Easter weekend would be wet at times. However, confidence in this being the outcome is low at this stage due to the range of possible outcomes being shown by the GEFS suite of runs. Most of these have a cooler but drier air mass over the UK during Easter.

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Posted at Mon, 07 Apr 2014 12:28:07


Frost risk new week

Temperatures recently have been well above average in much (I know the north has been cold and miserable at times) of the UK with winds coming from the south east  and then the south west. Things are set to change in the next few days with a weather front pushing east on Monday followed by clearer and cooler air from the west.

As some of you may have noticed this general development has been very well modelled and so has been possible to predict for a number of days. Ironically the details of the shorter term have proved a lot more difficult to nail down, with uncertainty about rainfall amounts this weekend for the Grand National and Boat Race!

Once that cooler air reaches us the risk of frost will increase and this could cause gardeners a few problems during next week. Here’s the latest temperature forecast for 6GMT on Tuesday from the GFS model, but remember a lot depends on cloud cover and small scale variations tend not to be picked up very well. What that means is chart may give a good indication of the broad picture, but if you live in a frost pocket and there’s not much cloud cover temperatures could be a tad lower. The opposite applies too with!

06_72_uk2mtmpmin

The frost risk could persist for several nights, but later in the week we could see cloud amounts increase. This often happens when high pressure becomes parked to the south west with murkier air drifting over the top of it and down across the UK. The cloud cover chart forecast chart for next Thursday afternoon currently shows this sort of thing with some patchy drizzle or rain also embedded in the flow. Remember this is a long long way off still and forecasting cloud cover 24 hours ahead is often difficult, but the picture it shows does seem plausible.

06_129_ukcloud

In summary a change is on the way with temperatures taking a dip. Despite this high pressure probably still the dominant feature of the weather next week so rainfall amounts probably not too high. It’s all quite a big contrast with what we were experiencing a couple of months ago when it seemed as though the rain would never end.

PS: Is there a correlation with high pressure in April and the summer which follows? If anything a warm April perhaps weakly correlates with a more unsettled summer, but this relationship isn’t one I’ve looked at in-depth. If anyone has a different view let me know.

Posted at Sat, 05 Apr 2014 12:14:28


Weekend weather update 2

Still looking mixed this weekend. The latest rain forecast chart for tomorrow afternoon is still showing a dampish picture for the Grand National at Aintree with a lot of cloud around. Not cold though with a south westerly wind blowing. It’s a similar picture across much of the country, but in the east it could be brighter with sunny spells developing for a time making it feel quite warm again.

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By Sunday it looks as though outbreaks of rain will be spreading north east. These could be quite light and patchy again in the south east so perhaps not too bad for the Boat Race taking place on the Thames.  Again temperatures still pretty decent for early April despite the cloud cover.

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Reasonable consistency on the general picture next week with  cooler and showery air returning from the west early in the week. High pressure probably building back mid-week with a frost risk returning. At this stage it’s looking quite promising for the London marathon with high pressure over the south west and air pollution probably not a major issue with winds having a westerly component rather than a continental one.

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Posted at Fri, 04 Apr 2014 10:51:29


Weekend weather update

The weekend weather continues to look mixed. The latest rainfall forecast chart for Saturday afternoon is showing quite a damp picture, so although I’d not expect heavy rain at Aintree for the Grand National it could be quite a damp and gloomy afternoon. Winds coming from the south west so temperatures pretty reasonable despite the cloud and drizzle. In the north it should be quite a lot milder than it is at the moment.

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Sunday isn’t looking too good either with weather fronts bringing a lot of cloud and a risk of rain for the Boat Race on the Thames. Temperatures still decent for early April, but in southern areas lower than we’ve had in recent days.  At least with winds coming from the south west air pollution levels should be lower than they currently are in London, so I guess that’s particularly good news for the rowers. Here’s the latest rainfall forecast chart for Sunday afternoon.

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What about next week? It still looking like cooler air will return from the west early on bringing clearer conditions. By mid week high pressure could be building strongly again over the UK, so potentially quite settled but cooler than it currently is in the south. As we head towards next weekend temperatures may be on the up once again with warmer air being pulled up from the south.

In summary the outlook is a mixed one. This weekend most of the UK is likely to be damp at times with drizzle or outbreaks of rain at times. Clearer and cooler air returning from the west early next week, but then high pressure building back over the UK and the chance of another warm up.

Chart viewer

Posted at Thu, 03 Apr 2014 10:46:48



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