Archives for December 2009

Snowy scenes to end 2009...

Ian Fergusson | 09:36 UK time, Thursday, 31 December 2009

Snowy scenes in the Cotswolds (Photo: Andrew Lockie)The forecast snowfall across higher ground of Gloucestershire materialised - eventually - earlier this week for a number of upland districts, notably in the Forest of Dean but also for parts of the Cotswolds.

Andrew Lockie has sent BBC Weather some wonderfully evocative shots of how things looked yesterday (Wednesday) morning around Broadway Tower on the northern Cotswolds escarpment. His excellent choice of black and white photography really captures the mood of a postcard-like winter vista in upland Gloucestershire. Two of his images are reproduced here.

So, we end 2009 on an increasingly cold note and 2010 starts in similar fashion, with largely dry and bright weather for New Year's Day but also the chance of some snow showers.

I'm watching developments closely for tomorrow, especially into the afternoon, as the somewhat complex and - in some respects - rather uncertain forecast signals a risk of showers developing into parts of the Westcountry where they'll surely prove wintry. 

At present, I'd estimate the likelihood of some snow showers at around 40% or so, but with such an elastic forecast this risk could become more prevalent... or wane entirely!

Andrew Lockie captured this evocative image of snowfall in upland GloucestershireBeyond that, the cold weather continues for a prolonged period and albeit next week sees the snow threat primarily confined to eastern and north-eastern parts of England, it's not impossible we could see some manifested into parts of the SW at times. One to watch...

Meantime, a very Happy New Year to all of you; thanks for supporting my blog and indeed our weather forecasting efforts at BBC West.  We've seen some very varied and occasionally dramatic weather in 2009 and I dare say 2010 will yield just as many topics to discuss here with you!

UPDATE: Thursday 31 December 2009, 10.45hrs:

The latest Met Office modelling of Friday night / Saturday morning is worth highlighting here. As stressed above, a lot of uncertainty remains... but there is a possibility of some snowfall (albeit perhaps 1-2cm only) sinking southwards into parts of the Westcountry, as indicated by the blue dots you can see in the attached time frames from Met Office predictive graphics.

North Atlantic Evolution (NAE) modelling of possible wintry precipitation sinking south on Friday night (image via UK Met Office)

Winter set to tighten its grip....

Ian Fergusson | 09:11 UK time, Monday, 28 December 2009

I hope you all had a good Christmas? I've returned to work this morning on our early shift and it's a busy - and complex - week of weather lying ahead.

The last days of 2009 have the potential to yield some severe, newsworthy winter weather across a broad swathe of England and Wales, including the Westcountry... at least at times.

The first looming problems will brew to our southwest this evening, as a spell of rain - heavy at times - spreads northwards to encounter increasingly cold air.  And as it does, the prospect of snow starts to appear tomorrow morning, albeit we're being purposely circumspect about the exact geography of where this transition from wet stuff to wintry stuff will take place.

It'll be a close call for much of our region. Quite literally, a distance of 10 miles north or south could make an abrupt distinction between seeing heavy rain or disruptive snow.

Met Office early expectations of rainfall and snowfall totals for Tuesday; likely focus for snowfall is highlighted in redThe image reproduced here - based on Met Office modelling - offers a reasonable guide to those areas likely to see snowfall (the contours and numbers denote precipitation totals in mm - be it rain or snow). I've highlighted the most likely focus for snow with a red boundary, but please don't take it too literally!  Even without any snow, the heavy rain won't be insignificant either: as this chart suggests, some hefty rainfall totals are likely, especially on higher ground across much of the SW Peninsula.

Effectively, the M4 corridor offers a rough forecast guideline: i.e., anywhere northwards from there stands a higher chance of seeing snow into tomorrow morning, with the situation developing to give further falls throughout the rest of Tuesday (especially later) and into Wednesday.

Winter scene on the Mendips at Priddy, Somerset (Photo: Geoff Dickson)More so than any other of our districts, I'm expecting parts of Gloucestershire to be badly hit later tomorrow, with the Cotswolds, Forest of Dean and perhaps lower levels seeing varying amounts of disruptive snow.  The higher ground of the county could see accumulations over 10cm (and perhaps as much as 15-20cm) and added to this mix is the wind, blowing snow around to cause drifting and doubtless some impassable roads.

Whether areas further south - i.e., much of Somerset and Wiltshire; Bristol and Bath - see any snowfall into tomorrow is much more open to doubt.

Most of lowland Somerset (i.e., excepting the top of Exmoor and Mendips) is forecast to experience heavy rain, rather than snow; however, it becomes a more 50-50 situation further north into the likes of Bristol, Bath and S. Gloucestershire.

And as last week amply demonstrated, it doesn't take very much snow to cause real problems in and around Bristol...

By Thursday, snowfall could become far more extensive across southern-central England and so if you miss the white stuff in the next 24-48hrs (as most of our region probably will), there's a high chance of catching it later in the week.  By New Year's Eve, we could - I stress, could - see some severe snowstorms developing into southern and SE England.... but that's currently subject to great uncertainty.

It's Snow Fun on the Roads....

Ian Fergusson | 09:51 UK time, Tuesday, 22 December 2009

One of the advantages of getting underway to work at 0335hrs is the joy of seeing fresh, virtually unblemished snow that has fallen through the night.

One of the disadvantages is then driving in it. And nearly crashing.

Early morning snow in Bristol (photo: Dave Harvey)

Snowfall early on Monday morning in Bristol - caused by a line of showers, focused off the Bristol Channel into a narrow swathe by converging winds - resulted in very localised scenes such as this (Photo: Dave Harvey)

Yesterday morning's journey to the BBC from Bradley Stoke was more akin to performing in one of those ice rallying events that the likes of Michael Schumacher occasionally participate in. Except, obviously, without his deft car control. Or crash helmet.

Treacherous road conditions from the snowfall overnight Sunday into Monday have proved a major news and general talking-point around Bristol the past 24hrs, but if you travel some 10 miles away from the city northwards, southwards or indeed westwards, you'd wonder what all the fuss was about.

This is because the snow was very localised - fed into a narrow swathe of North Somerset, Bristol, South Gloucestershire and North Wiltshire, but with rather little (or none) falling elsewhere that night.

The reason can be traced to the source: over the comparatively warm Bristol Channel (about 10C sea temperature), showers were able to build readily, fuelled by this warmth and given further emphasis as a low level breeze clashed and forced the growing cloud tops skyward.

As the showers blew-in eastwards on the prevailing westerly wind off the Channel, they readily changed complexion from rain and sleet-bearing on the coastal fringe of Somerset, to delivering snowfall inland. Temperatures in Bristol were down to around -1 at midnight and continued to fall steadily into the morning.

Filton, by way of example, recorded 3cm of lying snow by 4am on Monday morning - as I can attest from the amount I scraped off my car in nearby Bradley Stoke around the same time. Take a look at a selection of photos sent to us here.

The legacy has been a widespread freeze of lying snow and slush,  with very limited thaw. My journey to work today (Tuesday) was a good deal quicker but no less hazardous - especially on suburban untreated roads, which would make very adequate arenas for impromptu ice hockey matches, but are no fun to drive along.

We're watching further snow showers this morning, feeding into parts of coastal Somerset and Bristol and born by effectively the same processes that delivered Monday's snow.

Nothing quite as heavy or problematic expected here today, however, but some small accumulations possible locally at least.  We'll see further showers arrive from the west later on Wednesday too, but I'm not expecting them to turn quite so readily to snow.... but watch this space!

All Hail to the Hailstorms...

Ian Fergusson | 15:00 UK time, Thursday, 3 December 2009

  A hailstorm towers near Bristol, viewed here from Bradley Stoke, S. Glos. (Photo: Ian Fergusson)Us cloudspotter types have been spoiled lately, as the November weather generated all manner of spectacular skyscapes across the Westcountry.

Brushed to and fro above us, the clouds have come in innumerable forms lately, like a Constable or Turner landscape. This ever-changing natural vista has been courtesy of an omnipresent jetstream close by the British Isles during recent weeks, responsible for the run of unsettled weather.

December has started in largely similar fashion.

Today, a classic polar maritime flow has established from the northwest, bringing not only a chilly feel but also pollution-free skies and some spectacular clouds towering in the unstable air - such as those I've photographed here.

I was treated to some impressive Cumulonimbus cells passing swiftly by earlier today. Their tops, up at around 15,000 ft (4570m), were turning readily fibrous and wispy-looking as they became a gargantuan mass of tiny ice crystals (a process called glaciation) in frigid temperatures up there of -25 to -30 Celsius. Brrrr...

And the ice wasn't just remaining high above.

These clouds were readily bearing hail and judging from my vantage point, a fair swathe of it was falling for a while across some districts around Bristol and Bath.

Streaks of hail fall across South Gloucestershire, 3 December 2009 (Photo: Ian Fergusson)You'll find falling hail is actually quite easy to spot and generally simple to differentiate from shafts of falling rain.

In the second image I took - here on the right - notice the very distinctive white appearance of the streaks falling from this storm cell. Often dubbed 'hail streaks' or 'hail curtains', even in fairly low ambient light conditions they tend to be conspicuously white or light grey, compared to the dark grey or shafts of rain that often accompany them. Sometimes, the hail-bearing sections of parent cloud have a distinctive greenish colour.

Talking of rain, we'll be seeing rather a lot of that into the weekend. Late Friday night looks very wet indeed for a time and - just after Saturday starts on a dry note - a further spell of potentially heavy rain will arrive later in the day and overnight into Sunday.

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