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Forecasting attempting at a new level!

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My Thoughts On April

Three years ago to this day, High pressure began to build over the UK which lead to the warmest and driest April on record. Cambridge only recorded 0.4mm of rain, which is exceptional, with a maximum temperature of 23.9C on the 11th April 2007, with some places on this day along the south recording 26C. Yet the next month 131mm of rain fell, as a +ve NAO dominated with a Northerly tracking jetstream then bringing the wettest summer on record, with many places seeing more than double the average summer rainfall. But what will this coming April bring? And is there a correlation between the weather in April and the Summer?

Starting with Easter Sunday, A band of lively rain with the possibility of thunder will affect the SE and parts of EA, while in Northern Scotland, rain with hill snow will gradually die out by the morning. The day itself should be many dry with an isolated shower. Into the afternoon it will cloud over in the west, and by the evening will affect Northern Ireland and Ireland. Temperatures will range between 7C in the North to 12C in the South. The rain later in the day will spread North East into NW Scotland, NW England and may be a cause of concern because with snow melt over the hills of NI especially, it could cause localised flooding. The rain may persist into Tuesday in these areas, and will continue to spread northeast but otherwise mainly dry for all other areas. A warmer day on Tuesday, reaching up to 15C in the South to 11C in the North.

A Warm front will affect England and Wales on Wednesday, and will herald a change, with HP building from the South West. How warm and sunny depends where the HP will end up. Ideally for 20C+ you would want pressure to build to the South East which allows a warm southerly flow. That seems very unlikely though. Here is a chart from April 2007, in which that happened:
[attachment=99371:Rrea00120070411.gif]

The most likely place it will set up shop is just North of Scotland. This would result in days with sunny skies with a little cloud across western areas, but further east you would encounter more cloud. As of today, ECM would be the best solution for all areas. Temperatures will mostly be between 13-17C, 20C would be near impossible in this setup. The Atlantic will finally be put out of action for a while and will be welcomed by many (including me). How long will this theme last for though?

From the latest synoptics, it should last at least a week- 10 days. But over time I do think HP will begin to lose its influence and may 1. Possibly sink under Atlantic LP's 2. Sink southwards but heights may build again later in the month.
Intrestingly enough though, we still have the influence of blocking to the North with a -ve AO, but the northern arm of the jet has strengthened somewhat recently. Therefore, I would put the risk of a Northerly outbreak occuring between 2nd-3rd week of April at 25%. If one did occur, it would only be a temporary one and would be toppled quickly. I think the last week of April may be Atlantic dominated at this stage, but that is my guess and can easily change.
So in summary:

1st week: Wet and windy at first but HP builds from the South and West later in the week
2nd: Dry, settled, calm with some cloud especially in Eastern areas.
3rd: HP loses influence opening up a possible Atlantic attack or even a possible Northerly incursion
4th: Atlantic dominated, spells of rain interspersed with brighter and sunny spells.

Certainly no April 2007 on the horizon but it will feel pleasant in the sun, so enjoy the upcoming weather and Easter!

Ben_Cambs

Ben_Cambs

 

Spring Starting To Show Its Hand

Many places today broke the 10C barrier for the first time in a long while. Some places until today had not reached 10C for nearly 100 days. Shows the lack of mild that was evident during the winter. So what does the coming week have in store for us?

It will be a wet morning in Northern Scotland, with rain clearing Eastwards, with a few showers following in behind. Most other areas will remain dry and it will be bright with sunny spells interspersed with cloud. Northern and Eastern areas will be windy at times. Temperatures will be widespreadly 8-12C, with a westerly/north westerly wind.

Tuesday will be the same, dry and bright for all areas apart from a few showers affecting the Northern Isles. Again 8-12C maxima looks likely, but nightime will be cool especially in Eastern areas with a touch of ground frost possible in rural areas. Patchy rain will affect Northern and western areas on Tuesday night into Wednesday.

Wednesday and Thursday look likely to be the warmest days of the week, but in return the weather will be unsettled. Patchy rain and showers will affect northern and western coastal areas. The further South and East you go, it will be brighter with less chance of seeing any rain. Temperatures could reach up to 14C on Wednesday and Thursday in the SE, up to 12C in the North.
Thursday will see a band of heavy rain moving from West to East, which will affect most areas. Again temperatures will be up to 14C maybe 15C in a few spots in the South and between 11-13C in the North.

Friday will be a showery day with sunshine and showers. A slightly cooler day with maxima's of 9-10C in the North and 11-12C in the South.

What happens afterwards is still up in the air. I think it will turn cooler for all areas come the end of the weekend, with average-slightly below average temperatures.
The Southerly tracking jet will remain a southerly tracking jet for some time yet, with a slightly -ve NAO. This will help the cause that we are still at risk from Northerly incursions.

Ben_Cambs

Ben_Cambs

 

The Odd Sign Of Spring?

Well there is certainly signs of spring within nature this week. More plants such as daffodils, daisies etc have sprung out of the ground, the past two days have felt quite pleasant in the sun, but is Winter now over? Thats a question.

My definition of spring weather, which people can comment on if they want, are temperatures between 13-15C and quite settled days, of course there is always going to be a bit of wet weather involved too. So what will in the long term for potential Spring like weather?

Well this week looks to be mainly dry and quite bright for most areas, and with temperatures around average, it should feel quite pleasant in the sun. Later on in the week we have a more Easterly influence to our weather, which will drag in cooler temperatures and a breeze which might not feel pleasant at all. On Friday we have a trough/small low running down the Eastern side of the country, and although we have colder uppers, it should fall as rain on low ground, but possibly snow on higher ground above 150m or so, maybe a covering on ground above 200m or so. Potentially the SE could have a shot of a Easterly over the weekend, but details need to be firmed up. Most places will be dry though, as HP builds over us, the proper cold gets shunted into mainland Europe. After that IMO depends on what the Jet Stream decides to do. The NAO forecast is for a neutral NAO around Mid-Month, the same with the AO forecast too, some of the ensemble mean outlooks go for a positive AO, (which hasnt been seen for some while!) which would encourage a more northerly tracking jet, and then milder weather. Personally I can that happening at some point this month, but until then, the weather that we saw today looks to become the theme.

I see up until Mid March from this weekend being HP dominated, which most will welcome, with average temperatures by day and maybe some frosts by night. It should feel pleasant in the sun, as we get nearer to Spring Equinox.
What a winter it has been though, widespread snow and cold, for most of the winter there has been a -ve NAO and -ve AO which have been in deep negative at times. A southerly tracking jet for the whole of winter too!
What Winter 10/11 will bring I dont know, but IMO I wouldnt be suprised to see a winter similar to this!

Ben_Cambs

Ben_Cambs

 

Will Winter End?!?

My first and probably failed attempt at forecasting!

We have seen some very very impressive snowfall this week in Scotland, a great season for the Scottish Ski Resorts continues, and the signs are its going to remain that way for some time yet.

Tonight we see a Deep LP move in from the South West, which has already hit Portugal, NW Spain and W France and is moving towards us. Luckily, we miss out on the most damaging winds, which are on the southern flank of the LP.
Areas hardest hit will be roughly in a line from the Dorset Coastline to the Wash, at times some very heavy rain and on the South Coast winds gusting to 50-60mph, which may cause a little structural damage in a few places, but more worrying will be the rainfall, in places where river levels are very high, especially in the SE corner. It is a cause for concern and needs to be closely monitored, as in these areas there is a flood risk.
A wet day too for the Midlands, East and South Wales, and probably the rain will extend up to Yorkshire too. For N.England, Scotland and N.Ireland, it will be a dryer day, but later on rain will affect N.England too.
Temperatures will be cold, generally maximum's will be around 6C in the South, around 4C in the North.
There is a risk on ground above 250m or so for something more wintry in nature, perhaps a covering on ground over 300m, especially on Sunday Evening.
The LP clears off on Monday, affecting Eastern areas at first, but leaving dryer and brighter conditions behind. A cold day for the Northern half of Britain, 4C maximums, generally 5-8C in the Southern half of the UK, possibly reaching 10C in the SE corner where the warmer air of the LP has passed through.
Tuesday and Wednesday look dry and bright, a few showers on Western coastal areas (wintry in North West Scotland and The Shetland isles)

Potentially things could get very interesting from Thursday onwards. HP moves westwards and this allows in a much colder NE flow, and with LP not too far away, potentially next week we could see heavy snowfall across a large swathe of the country. More on this in a few days time.....


Winter has no signs of ending for the time being, and the models suggest no Spring weather!

Ben_Cambs

Ben_Cambs

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