Archives for February 2010

All eyes now on Sunday: wild weather arriving?

Ian Fergusson | 12:00 UK time, Thursday, 25 February 2010

UPDATE & CLOSING REMARKS, 08:20HRS, MONDAY 01 MARCH 2010:
I drove from Hertfordshire along the M25 and then westwards on the M4 during some of Sunday's worst conditions. The amount of standing water was especially treacherous on the motorways and unsurprisingly, the Environment Agency has issued a number of flood warnings in the wake of the heavy rain.

The Met Office's forecast of the most significant rain and winds affecting areas southeast of a line from around mid-Devon up to mid-Lincolnshire proved pretty accurate, as did the fairly swift clearance of inclement weather eastwards by around mid-afternoon.

Germany-storm-damage_28Feb2010.jpgThe storm caused a swathe of damage across parts of NW Europe, including here at Mainz, West Germany (Photo: AFP)

Sadly, the anticipated severe weather in France, Spain, Germany and other parts of NW Europe also became reality, costing the lives of at least 50 people. This BBC News report gives a graphic idea of just how badly many areas (especially in western France) were affected by Sunday's storm system. Indeed the French Prime Minister Francois Fillon has declared the event a national disaster, thereby freeing up funds to help businesses and communities recover.

You can read a number of eyewitness accounts of the storm here - described as "the worst I've ever encountered" by a woman in Persac, France.

The quieter, drier spell of weather now across southern Britain will bring a good deal of blue sky and overnight frosts, before conditions become more 'mobile' once again from Wednesday onwards. A cold easterly windy will be very noticeable and whilst many areas will remain largely dry, some hill snow is likely at times from Wednesday onwards in the SW and elsewhere; perhaps a chance of more significant rain, sleet and snow in East Anglia by the weekend.

However, after a continuation of this cold, blocked anticyclonic pattern, there's a hint of temperatures starting to return to the norm within the latter part of this coming fortnight. Fingers-crossed for spring!


UPDATE, 17.30HRS, SATURDAY 27 FEB. 2010 (amended 22:10hrs):
The storm is has undergone explosive deepening NW of Portugal and is crossing the Bay of Biscay.

Hurricane Force 12 winds are expected in some sectors of the shipping lanes there tonight and we've recently seen gusts around 70mph near Santander.

Damaging winds are expected into parts of western and northern France later tonight and through the morning. The sting jet potential (mentioned in my last update) remains a real concern on the SW flank as the development continues. The Channel Islands - where tides will also be high - are likely to see winds gusting around 60-75mph for a while at least, early in the morning.

On this side of the English Channel, conditions will readily worsen tonight as the winds increase and rain starts to sweep across parts of the West Country and along the south coast, especially from midnight towards daybreak. So, very wet and very windy is an adequate summary for a number of counties, but many of you in the west will see a steady improvement even by midday.

Southeast of a line from around mid Devon up to mid Lincolnshire, some heavy rain will fall at times into the morning, widely giving 15-25mm accumulations and potentially 40-50mm locally in some areas of the extreme south between East Dorset and Kent. Certainly enough to cause local flooding problems and the Met Office has now issued FLASH warnings to highlight this threat. Coastal and estuarine flood issues from storm surge, combined with high spring tides, are also a concern for parts of the SE and East Anglia especially.

The strongest winds - whilst always on the south side of the low - will nonetheless make their presence felt here in England, especially through the morning as the system moves steadily eastwards. The current Met Office modelling suggests pretty wild conditions for a spell tomorrow in the likes of Hampshire, Sussex and Kent. Heavy rain will be across much of the SE around midday and I dare say the inclement conditions will surely prove troublesome for people travelling to Wembley for the Carling Cup final.

By the time it kicks-off at 3pm, we expect areas west of around Swindon to be seeing improving weather; indeed, sunny but still rather breezy conditions will be across much of the West Country potentially by around 1pm, with the heaviest of the morning's rain having cleared eastwards by then. But the wet weather - albeit perhaps not especially heavy by 3pm - is still likely to be falling above NW London when the football match starts.

Monday and Tuesday, incidentally, look a good deal drier and quieter! But the legacy from tonight / tomorrow's storm across parts of France and NW Iberia could well be very newsworthy indeed, for all the wrong reasons.


UPDATE, 23.30HRS, FRIDAY 26 FEB. 2010:
Sunday's storm is now forming west of the Canaries.
Considering we're still watching an incipient phase - after which things will start to evolve quickly - and still many miles from our shores, the level of agreement between various forecast models on developments through the next 48 hours is quite noteworthy.

However, the last Met Office model takes the low slightly north of previous expectations by midnight Sat-Sun. The French Arpege model supports this idea, albeit with a somewhat less deep centre at the same timeframe.

So, no significant change - broadly speaking - from my last update,  other than the likelihoood of some stronger winds into the SE quadrant of England during Sunday.

Crucially however, a real (worrying) potential identified by the Met Office scientists is a sting jet feature likely to threaten parts of northern France. If this becomes reality, it could take a swathe of 60-70mph gusts also across the Channnel Islands - briefly - early on Sunday morning. The impact on parts of France could prove far more newsworthy.

Around 20-40mm of rain is signalled from the latest Met Office modelling across the SE quadrant of England during Sunday, with snow into parts of the Midlands and perhaps southern-central England north of the M4, falling across areas mostly above 200m, at least for a while. The risk of coastal flooding is certainly a concern for some areas (see last update).



UPDATE, 10:30HRS, FRIDAY 26 FEB. 2010:
Generally good forecast continuity from the the Met Office's Global Model continues to offer a very similar story to my last update,
with Sunday's storm expected to track across the Brest Peninsula and east-northeast through districts of northern France.

The latest synoptic chart from the Met Office for midday on Sunday - reproduced below - affords a very graphic indication of the tightly-packed isobars expected along the southern flank especially.

Met-Office_Synopsis_280210_.jpgThis will surely bring a spell of very severe weather across parts of N/NW France, where winds are forecast to gust up to 80+mph, doubtless causing a swathe of disruption and potential damage. Earlier, the storm is likely to have caused similar problems in NW Spain, before it crosses the Bay of Biscay tracking northeast.

For much of southern England and Wales, however, the likelihood of heavy rain remains our primary focus of attention, with the Met Office advising of accumulations around 25mm (1 inch) expected fairly widely and maybe double that in some districts. Local (inland) flooding is thus a matter of concern; perhaps also some problems developing in some coastal areas, with high tides on Sunday combining with the surge effects generated by strong winds.

Those winds - while certainly touching gale or even severe gale force, especially in the extreme south - are looking somewhat less menacing for the British Isles given the expected track of this low (albeit, as noted above, a far more dangerous outcome is expected across the other side of the Channel).

A continuing forecast complication is the chance of snow during Sunday as the storm departs further eastwards, increasingly drawing colder air off the North Sea and wrapping this around the system's north and northwest flanks.

The current Met Office view is for snow to fall across parts of the Midlands - including to lower levels - and across into Wales, but the southern extent of this potential remains unclear. Areas northwards of the M4 (e.g., perhaps including parts of Glos., Oxon and environs) look more at risk of at least some transient snow, but at lower levels it's unlikely to settle readily.



UPDATE, 20:00HRS, THURSDAY 25 FEB. 2010:
We're now entering a very interesting period of model-watching regarding developments for Sunday.

The Met Office's Global Model - showing pretty good continuity of late - has shifted the likely track of the storm just a tad to the southeast of previous runs. It's noteworthy how Arpege, the French forecast model, prefers an even more SE and slightly faster progression. And for that matter, so does GFS (the US global forecast model).

So which will prove correct?

The French solution has the 'eye' of this system, at a surface pressure of 976mB, making landfall around the Mouth of the Loire at midnight on Sunday morning. The Met Office version of events keeps a slightly slower and more northerly track than Arpege - with the low pressure centre still above northern Spain and entering the Bay of Biscay at midnight Sunday AM, before tracking up across the Brest Peninsula.

Either way, a swathe of strong winds - potentially up to 70kts and decidely perilous - is signalled to cross parts of N/NW France (with some of the most severe winds close to Paris) during Sunday, while heavy rain and windy weather affects much of southern UK.

By late Sunday, with the low spinning away along northern districts of Benelux, a 'wrap-around' of colder air floods across the Midlands, Wales and parts of the West Country. The current lower-resolution Met Office modelling calls for between 2-6cm of snow from this 'tail-end-charlie' feature, including for the likes of upland Gloucestershire. However, that's very speculative and for sure, it's the heavy rain  and associated flood potential that remains our main focus for attention.

If the current model trends continue, Sunday will give a spell of truly severe weather for parts of northern France and environs.

Meantime, it'll be a distinctly wet, windy but perhaps not 'severe' day of weather - in the strict sense - for much of southern Britain.

Quite understandably, continuing uncertainty regarding the precise track of this storm is the reason why the Met Office has held-off issuing advisories or warnings, for now, at least. But as ever, I'll update you on all the latest forecast detail tomorrow...

 

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This winter's fascinating and often dramatic weather changes complexion now for a while, with some distinctly wet and quite windy weather arriving later today (Thursday) and overnight.

Then - after generally drier, quieter conditions on Friday and Saturday - a much more troublesome-looking spell of weather is expected for Sunday.

atlantic-synopsis-friday.jpgDown in southeastern reaches of the North Atlantic Ocean, way east of Florida, the potential for trouble arriving by Saturday night is already brewing.  A wave-like disturbance in the atmosphere is gathering pace and will develop into a deep mid-latitude cyclone as it moves northeast.

The charts on the right show the expected track of this rapid cyclogenesis event, with the low centre moving towards NW Europe across warm oceanic waters and turning ever-more potent with each passing hour. If you're interested in the deeper science, the development is expected to be akin to the atlantic-synopsis-saturday.jpgconceptual model known as Shapiro-Keyser. In short, it could get pretty nasty.

Current expectations take the feature very close to Madeira - where efforts are underway to recover from last week's deluge and the tragic consequences - before it buffets NW Iberia with strong winds and heavy rain.

As the Sunday chart shows, the track continues up across the Bay of Biscay, but precision on the exact path it'll follow is yet to be determined. The Met Office's current expectation sees the centre of the low sweep through the English Channel, with strong winds especially on it's southern flank atlantic-synopsis-sunday.jpgaffecting coastal regions of France but also some coastal districts of southern England.

The impact across the British Isles will vary: for the West Country, our primary concern is a spell of potentially heavy, persistent rain falling onto already saturated ground. The spectre of local flooding is a worry in some areas of southern England.  The winds will also be a feature - possibly gales or severe gales in exposed districts - albeit at least most trees are without leaves, hopefully mitigating the risk of widespread wind damage problems.

The north and northwest flank of the low will progressively entrain colder air, offering a temporary risk of snow over at least higher ground. The current Met Office model suggests such a risk through parts of the midlands, extending down into parts of Wales and the West Country - but there's a great deal of uncertainty about how extensive such snow could become, as the low tracks east. It's the heavy rain that gives us greater concern.

The Met Office is assessing the details and disparity on the rate of deepening, track and precipitation likely to arise from this storm; understandably, they're holding-off issuing formal advisories and warnings until the regional bias of risk is clearer. It's very much a story in motion - I'll keep you updated.

A wet week lies ahead....

Ian Fergusson | 18:34 UK time, Monday, 22 February 2010

UPDATE, 08:10HRS, TUESDAY 23 FEB. 2010:
Little significant change of emphasis today, with the prospect of seeing snow falling even to low levels at times today across many of our districts but especially into upland areas above 150m AMSL.

Exmoor and environs will start to see some snow by mid to late morning - possibly 2-5cm here and across some other high ground of Somerset - where the Met Office now has a severe weather warning in force.

By around midday, the main band of precipitation will be draped through Bristol, B&NES and much of Wiltshire, again offering snow for some, perhaps even down to street level in the likes of Bristol & Bath but (like on Exmoor) turning readily back to rain as the afternoon progresses.

The Forest of Dean and parts of the Cotswolds will see snow through the afternoon, probably heaviest over the Forest itself - again, 2 to 5cm likely here and quite probably some level of disruption on the smaller roads. It'll all ease away northwards this evening, changing to rain from the south.

UPDATE, 21:20HRS MONDAY 22 FEB. 2010:
The latest NAE run offers a broadly similar story BUT with an increased snow potential later tomorrow morning and early afternoon into a broader area of Somerset (especially upland areas, I do stress) and northwards through Bristol, B&NES, N. Wilts and into Gloucestershire.

However the emphasis for significant snow still remains primarily across Exmoor and into the Forest of Dean. Elsewhere, other than transient snow, it's still principally a rain story.

So, a lot of wet weather about from after the morning rush-hour onwards but it's quite possible we will see some snow at lower levels in a few districts, albeit higher ground will be distinctly favoured.

So, we expect around 0-2cm in Somerset (and parts of North-Mid Devon) above 100m and possibly 2-5cm in any of these areas above 300m.

Timings suggest mostly dry weather, some drizzle aside, during the morning rush-hour for much of our region; then snow over Dartmoor and Exmoor by around 9am; into the S. Glos area by around midday and then spreading northwards. By around 6pm, it should all be falling as rain as the Wet Bulb Freezing Level rises widely above 1000m.

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After today's snowfall, albeit a fleeting experience for many, it looks like a good deal of wet - rather than white -  weather lies ahead through this working week.

Windy at times, too. And on the thermometers at least, turning fairly mild.

Some heavy and at times prolonged rain will affect many districts as a series of low pressure systems sweep into the SW off the Atlantic. So what about the threat of snow?

Mostly minimal.  However...

Tomorrow (Tuesday) is likely to offer some snow over Exmoor and the adjacent upland areas of Somerset, with snow also probably falling into the Forest of Dean.   It'll likely arrive later in the morning and into the afternoon, whereas we're expecting most - if not all - of the remainder of the West Country to see rain. The greatest risk of snow will be for any areas of high ground above 150-200 metres, facing eastwards.

The map below gives the Met Office's latest idea of how the rain-snow geography will look by the end of Tuesday. The yellow line shows the expected confines of areas seeing more than 1cm of snow; the orange line, for areas seeing more than 3cm. Don't take it literally - but probably a useful guide!

new_snow_prognosis_tuesday.jpgYou'll see some critical differences compared to the snowfall forecast for and experienced during today (Monday), especially the more westerly bias expected on Tuesday. Moreover, the threat of significant snow to lower levels lies a good deal further north - hence the high likelihood of rain for most of us at lower levels.

By late tomorrow afternoon, significantly milder air than we've seen of late will have flooded across southern England in the lower levels of the atmopshere - helpfully curtailing the risk of snow, yes, but certainly not really making things feel much 'warmer'!!   In fact, wherever you are in the West tomorrow, it will remain an essentially cloudy, wet story until after nightfall.

Although Exmoor isn't included on this map - and hasn't really been mentioned in many TV forecasts either - it's my 'tip of the day' and I expect some of the moor will see some snow, perhaps more than a few centimetres.  So to recap, Exmoor and the Forest of Dean are my expectations for any 'proper' snowfall during Tuesday.

The rest of the week carries no significant chance of snow; indeed quite the opposite, as we see repeated spells of rain. The spectre of localised flooding could become an issue by the end of the working week, but I'll keep you updated on the expected developments.

butterfly_ianfergusson.jpgOh, and incidentally - I photographed (right) a Red Admiral butterfly (Vanessa atalanta) on Saturday, basking in comparatively warm sunshine here in Bradley Stoke. A wonderful sight and the first I've seen in 2010. Not many of these distinctive insects survive even an average British winter - their population each year is boosted by migrants from continental Europe. Thankfully, this particular specimen was too high on a wall for my cat, Pickle, to catch and eat it... but was it a sign of impending spring?

Well, the longer-range forecasts progressively squeeze the snow threat up into the Midlands and then eventually just to Scotland.... but at the same time, some distinctly unsettled (if not distinctly cold) conditions look likely to dominate across the south.  So keep those t-shirts tucked-away in the drawer for now... but have the umbrella close at hand!

More snow possible for Monday?

Ian Fergusson | 21:11 UK time, Saturday, 20 February 2010

UPDATE: 09:00HRS, MONDAY 22 FEB. 2010:
So, further snow being reported quite widely across our districts - from as far afield as Burnham-on-Sea and Weston-super-Mare across to Avebury in Wiltshire; albeit in most lowland areas it'll be a transient feature and unlikely to settle to any great degree. 

Different story into the NE areas of Gloucestershire and Wiltshire, where the snow will readily accumulate for a while this morning and indeed into the afternoon, before gradually easing-away eastwards around mid-afternoon. 

Worth adding that tomorrow (Tuesday) could yield similar weather in many of the same areas. I'm expecting to see snow over Exmoor early on Tuesday - possibly quite heavy - with a broad swathe of rain again at lower levels but this turning progressively to snow from around the M4 corridor northwards. The risk of heavy snow tomorrow for the Forest of Dean is greater than today; definitely a situation we'll need to monitor closely. For what it's worth, the rest of the week promises further spells of distinctly inclement weather and the accumulation of rainfall could well cause localised (surface water) flooding problems for some areas.

UPDATE: 07:00HRS, MONDAY 22 FEB. 2010:
We now have snow falling in parts of Gloucestershire (Forest of Dean and Cotswolds), plus along stretches of the M4 corridor in Wiltshire, especially near Swindon and Marlborough.  I'm expecting snowfall over Exmoor too and albeit rain for most other districts this morning, a sleety mix and sporadic wet snow is quite possible even at lower levels. The risk of snow should vacate the Forest of Dean quite readily this morning, but conversely it will remain across the northern Cotswolds for a more protracted period into the mid-afternoon. Here, you might see 5cm or more falling in some areas.

 

UPDATE: 04:00HRS, MONDAY 22 FEB. 2010:
Well, the new model run again flips-back to the original idea of a possible snow threat for Gloucestershire this morning
- hence the Met Office has issued a warning for this potential.  Still looks like rain elsewhere in our region - with the possible exception of the most northerly districts of Wiltshire. I suspect Gloucestershire will be on the very cusp of the rain-to-snow transition, but once again the upland areas will have the greatest chance of seeing snow.

UPDATE: 10:00HRS, SUNDAY 21 FEB. 2010:
The latest modelling for Monday from the Met Office will bring a major sigh of relief for Gloucestershire commuters growing weary of negotiating snowbound roads.

The risk of significant snow for Monday morning has been drastically reduced on the new NAE run, albeit with some still signalled into the Midlands and across to The Wash -  hopefully leaving Gloucestershire free of a further disruptive event.

The next model runs will be critical in confirming the positioning of the area where rain could change to snow (if any) - it's still a tad knife-edge for extreme north and north-east Gloucestershire, but for all our other counties, rain will surely be the result rather than snow.

Indeed, the entire West Country - and for that matter, all of southern England - looks set for a very wet spell during the early morning tomorrow, with some heavy rain developing at times across many districts but clearing steadily eastwards towards midday. By early afternoon, all of our region - with the possible exception of east Wiltshire - should be dry, with cloudy and cold, breezy weather then prevailing for the remainder of the daylight hours.

Further wet (and rather windy) weather will affect us all on Wednesday and on Thursday; by Friday, there's hints of colder air seeping back southwards again.  But for now at least, any threat of significant snow looks effectively minimal for the West Country, whereas the rainfall will certainly grab our atttention!

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It's likely some of you, especially in more northern districts, will see some snow tomorrow (Sunday) morning at least falling, if not settling.

We expect a band of showery outbreaks of rain, sleet and some snow to cross eastwards, but it's the risk of widespread ice that causes us most concern, rather than any snow per se.

However, the likelihood of seeing some lying snow tomorrow in the West Country is greatest in Gloucestershire.

And yet again, it's Gloucestershire in the crosshairs for potentially more wintry weather at the start of the working week...

As if it doesn't need repeating, 'uncertainty' is yet again the watchword to stress for this early blog stab at the forecast but - with the risk of snow now at 40% - the Met Office has duly issued an advisory for Monday morning covering much of our region.

In many respects, the broader set-up is similar to last Thursday and the resultant snow this time - if indeed we see any - may follow a geographic spread that's much the same.

The models indicate a risk of snowfall up to 10cm in places and I'm again focused on Gloucestershire as the area at highest - or perhaps only - risk of anything disruptive in the West Country. I suspect most areas will see a day of (sometimes heavy) rain and windy conditions rather than snow, but the extreme north of Gloucestershire and Wiltshire might experience something much whiter than wetter.

The timings are currently a tad unclear, but snow could fall over upland areas of the county by Monday morning's rush-hour onwards and then perhaps to lower levels as the morning progresses.

It's very important to stress some key differences between various models in their handling of Monday's evolution and associated snow potential. Some paint little or no snow whatsoever across southern England; whereas others - including the latest Met Office NAE and USA's GFS - suggest otherwise.

Between these two, there are differences in the regional bias of snow risk, albeit crucially the actual variance is not significant if considering the resolution of the models.

Below, I've annotated a graphic showing how the NAE, as interpreted through BBC graphics, offers snow at 12pm on Monday from SE Wales up into the Midlands (with 5+cm snow contour in blue).

snow-prognosis-monday.jpgFurther south, including into London and the Home Counties, the GFS solution for the same time - outlined in red - suggests similar snow totals but affecting a different swathe of the country. Tricky, huh?

This sort of key difference in bias, over fairly small distances in forecasting terms, speaks volumes about just how difficult it can be to judge snow risk at this sort of lead time and to make informed, timely decisions when issuing public advisories and warnings.

Last Thursday the Met Office got things pretty much spot-on; let's see how things develop for Monday....  Groundhog Day?

Wet Wednesday, White Thursday?

Ian Fergusson | 09:08 UK time, Wednesday, 17 February 2010

UPDATE 07:00HRS, FRI. 19 FEB. 2010:
It's a final update for this particular blog entry - and I suspect there'll be some further lively (and potentially disruptive) weather to forecast and discuss at times next week, too, especially Wednesday but perhaps through Monday, too.

Meanwhile - I thought I'd share with you some more photos sent to us here at BBC West of yesterday's snowfall. Thanks very much to those of you who took time to send these to us!

The first (below) shows treacherous road conditions at Wiveliscombe in Somerset, taken by Anna Corbett

The second - taken by Linda Atkins - shows the depth of snow near her home in Cutcombe/Wheddon Cross on Exmoor - "about 5 inches", she tells us, as her photo quite clearly testifies!

Picture 3 is from Cam, near Dursley, Gloucestershire - taken by John Mace of the snow that fell in his back garden yesterday.

The 4th photo, from Alison Napier, clearly shows the amount of heavy snow that draped the Brendon Hills of Somerset throughout yesterday. A Winter Wonderland indeed!

Photo 5, taken by Frances Ring, illustrates very well how much snow fell yesterday across the Forest of Dean in Gloucestershire. Her photo - taken this morning at daybreak in Shortstanding - looks over Joyford, towards Edge End. "We had about six inches of snow here," Frances tells us.

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Cutcombe_Linda_Atkins.jpg

Cam_snow_John_Steamy.jpg

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UPDATE 12:30HRS, THURS. 18 FEB. 2010:
The snow is falling thick and fast here in Bradley Stoke, South Gloucestershire, as I write - and it's now quite readily settling after a somewhat hesitant start. However, it will take a fairly prolonged spell of similar intensity to really stick with any longevity - not least on the main roads, where this wet snow is quickly turning to slush (and creating a lot of standing water on some routes).

Our expectation is for further snow to fall on-and-off between now and mid-evening for a number of areas in West Somerset (Exmoor), Bristol, B&NES, South Glos., much of Gloucestershire and North Wiltshire.  However, for a while the snow prospect will very much depend on the intensity of the precipitation (i.e., heavier spells helping bring the Wet Bulb Freezing Level down to low level, through a process of evaporational cooling).  Towards the evening rush-hour, snow could prove more widespread - certainly across Gloucestershire - and I'd imagine the return journey home for many commuters on various routes such as the A417 across the Cotswolds could become decidely tricky in places.

The graphic below shows the UKMO's expectations of snowfall by 6pm this evening. Those of you who have followed this blog entry since the start will note how little the overall geographic story and timeline has changed from original forecast predictions; indeed the Met Office's pinpointing and warning of this event has been very good, in my opinion.

snowfall-thurs-18z.jpgUPDATE 10:00HRS, THURS. 18 FEB. 2010:
Many thanks to Chris Binding of Luxborough, Exmoor, who just sent me this photo showing the amount of snow already settled in his district - he estimates around 10cm (4 inches) in places already!

Snow in Luxborough, Exmoor, photographed by Chris Binding
UPDATE 09:00HRS, THURS. 18 FEB. 2010:
The snow is now falling thick and fast in Bristol, Bath and environs... but whether it will readily settle is another matter! We shall see... I'm sure it will settle in S. Glos and Gloucestershire.


UPDATE 08:10HRS, THURS. 18 FEB. 2010:
A quick update in between radio broadcasts!  The forecast evolution today follows largely the pattern already outlined below - perhaps somewhat less in terms of snow totals expected but essentially the same story, so the early warnings remain in force.

We've just had reliable reports of snow falling in Exmoor (already 3-4cm in places); ditto Porlock, West Somerset - causing some traffic problems there - plus parts of the Forest of Dean and around Bath. So the process of seeing rain turn to sleet and snow is already underway for some areas.

If you can report on any snowfall in your own areas today, please feel free to do so here on the blog - I'm ensuring these reliable reports are fed back to colleagues at BBC Weather Centre and to the Chief Forecaster at the Met Office Operations Centre in Exeter. It's all very helpful in honing the forecast detail!

 

UPDATE 19:40HRS, WED. 17 FEB. 2010:
At this stage we can start to offer a bit more forecast detail on the likely snow amounts expected during Thursday across the region...

These synthesised estimates (and I stress estimates) are based on the Met Office's high-resolution modelling (UKPP) of fresh snow depths by 9pm tomorrow evening. It'll be a rather narrow band of heavy / disruptive snow developing - hence many areas across the West Country will see little or nothing from this; others, conversely (especially, I suspect, parts of W. Glos) will see quite a bit. I'm still leaning towards this being a predominantly Gloucestershire / NW of M4 corridor event in terms of truly disruptive snow.... there's still time to be proven wholly wrong, however!  Anyway, here's those estimates:

Somerset: Lowland areas seeing predominantly rain to a dusting of snow (0.1cm). Exmoor: 5-10cm. Quantocks: Up to 5cm. Mendips: 2-5cm but variable (UKPP suggests very little here and over Blackdowns, surprisingly).

Dorset: Lowland areas only rain or a dusting; upland areas of West Dorset up to 5cm

North Somerset: 1-2cm; but very variable with some areas seeing only a dusting

Bristol & environs: 1-5cm (greatest in northern districts and potential for >5cm)

Bath & NE Somerset: 1-5cm (greatest in northwest districts)

Wiltshire: Very patchy coverage; rain and sleet for many but up to 2cm in northwest

South Gloucestershire: 2-5cm, possibly >5cm locally to north and across highest ground

Gloucestershire: Forest of Dean especially prone; 5-10cm or more possible here and across towards Gloucester, Tewkesbury and Cheltenham. South Cotswolds: 2-5cm; North Cotswolds: 5cm fairly widely; 5-10cm in NE districts.

The images below shows how the latest Met Office NAE model - shown here in BBC graphics representation - takes the risk of snowfall across a number of districts up into the Midlands into the evening rush-hour and towards 9pm:

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latest-fcast21zThurs.jpgUPDATE 15.45HRS, WED. 17 FEB. 2010:
There's growing continuity in the general weather developments tomorrow, if the midday NAE run is to be believed. However, some uncertainty exists over just how cold (or  not) the air will be at lower levels during the earlier part of morning. The idea of snow starting to fall much later in the morning - towards midday - is still the most likely outcome.

The Met Office early warnings cover a fair swathe of the West Country's more northerly districts, albeit I'm yet to be wholly convinced about the risk of any significant snow for North Somerset (Mendips aside), Bristol and lowland adjacent areas... I wouldn't be at all surprised if the transition from rain to snow lies somewhere a bit further north, such as across the Forest of Dean and southern Cotswolds, but I'll keep you updated on any views - divergent or otherwise - from the Met Office!

In any event, as I'm broadcasting our breakfast TV and local radio weather output throughout tomorrow morning, it'll be my own forecasting headache to tackle!

 

UPDATE 11:00HRS, WED. 17 FEB. 2010:
The latest NAE assessment this morning - completed since I wrote the original blog below - repeats the snow risk across broadly the same districts and suggests tomorrow's events could prove quite disruptive and noteworthy. 

Consequently, early warnings (>60% chance of severe weather) have now been issued by the Met Office for the following parts of the West Country: N. Somerset, B&NES, Bristol, S. Glos. and Glos. 

Advisories remain in force for Somerset and Wiltshire.

You can read the detail of the current warning / advisory status here.

 

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The second half of this week is a forecasting headache - not least the next 48 hours, as we keep a close eye on the potential for further snow.

And possibly quite a lot... at least for some areas.

Today's wet weather also has the potential to turn wintry as it spreads northwards across upland Gloucestershire, albeit we're expecting any significant snowfall during this afternoon to appear largely up into East Wales, the Marches, parts of the West Midlands and towards Manchester. So for most of the West Country, bar some rather fleeting spells of wet snow and sleet, it's effectively a wet Wednesday...

But what about a white Thursday? Tricky for the detail, this one!

'On paper' at least, the ingredients are in place to bring a swathe of snowfall - potentially significant amounts - into areas from around Bristol, Bath & Cardiff northwards into Gloucestershire, the West Midlands and across to Lincolnshire as a front pivots itself across England, associated with an area of low pressure centred - by around midday Thursday - somewhere around Lyme Bay.

It's important to note that different forecast models handle the associated snow risk to varying degrees. Some underplay it considerably.

The Met Office's NAE (North Atlantic Evolution) model - which effectively 'drives' the raw weather graphics across each 48-hr period you'll see on our daily BBC TV forecasts - offers a distinctly pessimistic outcome (unless you are a snow aficionado!) compared to various other computer solutions.

The chart below, generated from our bespoke Weatherscape XT broadcast graphics system, replicates how the Met Office model paints a snowy story developing across a number of districts by 6pm on Thursday. 

snowfall-prediction_thursday-180210.jpgIt actually begins to turn rain to snow from around late morning onwards in the same broad area, aided by a distinctly chilly - and foggy - start to the day, as temperatures fall readily tonight to 0C even in the centre of Bristol and other large urban areas and more like -1 to -3C out in the countryside. 

I've annotated the zone where heaviest (and perhaps newsworthy) snowfall is possible; with over 10cm signalled in a few spots but stress this is highly speculative - we're awaiting further runs of the model to see what level of continuity it provides (or not).  As you'd rightly expect, the Met Office will not upgrade the existing advisories for this potential event to an early warnings until we're seeing the 'whites of it's eyes' - literally!

And yes - as ever - I'll update you later today based on any new analysis and forecast expectations... will this one become a damp squib or a whiteout?

A little snow expected for some during Friday morning...

Ian Fergusson | 20:13 UK time, Thursday, 11 February 2010

UPDATE 09:00hrs, FRIDAY 12 FEB. 2010:
So, a few light snow showers reported across the expected areas in the past 4 hours - at RAF Lyneham, RNAS Yeovilton and one or two other spots; also a dusting in some parts of the Cotswolds according to some local observers... but that's likely to be the lot for today in terms of anything wintry!

Next week's forecasts will be interesting, for sure. Much more unsettled generally; still essentially cold and a complex mix at times of rain, sleet and snow accompanied by some windy weather.

Whether late Monday into Tuesday brings snow for parts of the West Country remains to be seen. The potential is there, but the various forecast models continue to show a fair degree of disparity (and they continue to do further into next week, too).  Until their continuity improves, it's very much an uncertain situation - watch this space and I'll endeavour to keep you abreast of developments.

 

UPDATE 05:10hrs, FRIDAY 12 FEB. 2010:
The latest Met Office modelling offers even less emphasis of snow showers into the West Country this morning - perhaps a dusting here or there in Wiltshire and east Gloucestershire, but really I doubt we'll see much else! Some rain and occasional patchy snow has been falling further east this morning around the Home Counties, but it's all very temporary in nature.

Worth adding that any wintry showers this morning will tend to become a rain / drizzle mix progressively as the day continues - so any snow reports this morning are likely to prove rather fleeting as most!

 

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It's another brief blog update - I'm into bed by 9pm this evening (oh yes, it's a recurrent theme in my life!) and by the time I'm driving to BBC Bristol around 3.30am tomorrow, some of you could have at least a little snow falling... enough to at least garner some attention.

It's by no means a spell of disruptive snow like some events earlier this winter (or indeed last February). Much lighter, but a temporary covering certainly possible in a few localities. So, I'm expecting to be spending time on certain BBC local radio breakfast shows tomorrow morning (Friday) - notably Wiltshire, Swindon and Gloucestershire - talking in my forecasts of light snow accumulations by the morning rush-hour. Exactly where is the key question I'll tackle at the time! 

A dusting for most; maybe a centimetre or so for some of you in Wiltshire especially. So nothing significant but nonethless, enough to warrant this blog entry - especially after a largely dry week (well OK, some impressive, if fleeting, snow showers aside!).

And what is causing the Friday morning snow potential?

We're watching an upper air feature that's developed north of Shetland - a shortwave trough - sinking steadily southwestwards across the British Isles tonight. Expectations take it on a track down from eastern England across the Midlands, into southern-central counties and parts of the West Country by tomorrow morning.

It's leading edge is likely to offer some light to moderate snowfall for some localities - starting (for our region) in parts of east and upland Gloucestershire and north Wiltshire around the early hours (say 3-4am) and then progressively southwards and somewhat westwards towards daybreak. It's possible the wintry showers will take a while to fade for some areas - perhaps continuing into the early afternoon across some parts of Wiltshire, for example.

It's just about possible some light (and at times perhaps slightly more significant) snow could fall in Bristol and Bath / B&NES, for example; ditto east Somerset and down into parts of Dorset and east Devon. However, I stress that the main West Country focus is most probably Wiltshire, at least based on our current expectations.

It'll be interesting to see how the morning outcome matches the forecast prognosis - this signal for a spell of light snow early on Friday has been consistently present in the Met Office (NAE model) forecasts run during the last 48hrs.

So - just to re-stress, not anything heavy by way of snow tomorrow and perhaps rather patchy in nature - but please do add your own observations here on the blog if you see snow tomorrow!

Incidentally, next week continues cold and a good deal more unsettled. I'll update you in due course...

A milder, wet & windy interlude now develops...

Ian Fergusson | 08:52 UK time, Monday, 1 February 2010

UPDATE, 12:40hrs, FRIDAY 5 FEBRUARY 2010:

Almost feeling like spring today, isn't it?

We've seen some glorious morning sunshine and temperatures widely reaching 10C (50F) today across the West Country. However, the clouds are tending to grow more readily as I look out of the window here in South Gloucestershire and yes, we'll see some showers across some districts, some potentially thundery. Nonetheless, it's a pretty pleasant end to an otherwise largely inclement working week!

So, on to the future... remember where you put the ice scraper before this mild week began? Best to try and locate it once again...

My previous blog entry hinted at the return of colder weather this month and indeed that's now firmly on the cards for next week. However, just how cold things will get - and for how long - remain aspects of considerable forecast uncertainty.

For the most part, I'm expecting our region to experience a largely dry, increasingly cold, frosty but otherwise rather unremarkable spell of weather for at least the first half of next week and quite possibly for a few days beyond that.

The current Met Office forecasts herald little risk of significant snow anywhere next week across the British Isles and especially so for the SW and many southern-central areas of England. 

However, we're expecting some accumulations to develop through Tuesday and Wednesday in eastern England, including parts of East Anglia and down towards the SE, as the increasingly cold air occasionally feeds-in snow across the North Sea to our shores.

There's also always a risk that Atlantic systems could progress far enough eastwards, into the pooled cold air, to bring snowfall into the West Country at some point later this month. Of course, we've seen this sort of snow-bearing mechanism already at work through this winter and a repeat performance is by no means impossible. On present reckoning however, it's an outcome of very low probability - at least for the next week.

Late next weekend (Sunday 14th) - based on the very latest Met Office modelling - there's a prospect of heavy rain arriving into the SW and parts of the South of England, from which some snow inland (away from the extreme SW) is a low probability consequence: indeed, less than 20% chance based on current analysis.

The forecast through to the end of the coming fortnight (10 to 15 days ahead) continues cold, with some potentially harsh overnight frosts for many but - as yet - a very muted signal for any prospects of heavy snow, despite a chance of the weather turning a tad more unsettled and windy at times.

I do stress it's all subject to change - I'll keep you updated through a new blog entry in due course.

 

(ORIGINAL ENTRY follows)

If you're a motorist, you've probably fumbled for the ice-scraper beneath the passenger seat this morning.

However, after today's frosty start, it's unlikely you will be needing it for the week ahead...

Indeed, at times over the next few days it will seem noticeably mild - certainly compared to much of the winter thus far - as spells of wet and windy weather spread off the Atlantic to give heavy rain in some districts during Tuesday, Wednesday and Thursday.

Across north-east England and indeed southern Scotland, we're expecting the colder conditions to prevail and here the advancing spells of rain will turn to snow at times. But there's no real risk of any snow for us here in the south.

Temperatures for most of us will be around the seasonal average - perhaps a notch higher for a while into Wednesday and Thursday - but we're still expecting things to turn somewhat colder again later the following week.

met-office-synopsis-friday05feb-12z.jpg

The latest Met Office synoptic chart for midday, Friday 5 February 2010. It continues a theme of a somewhat milder - and wetter - flow prevailing this week, as Atlantic depressions cross the country to bring some spells of heavy rain and quite strong winds for many districts.

The prospect of a profoundly cold spell of weather, as the Met Office suspected could arise when I wrote my last blog, is not altogether impossible but hangs in the balance.  Turning colder - eventually and by a rather uncertain margin - still remains the expected outcome after this milder interlude.

Based on current analysis by the Met Office, the most likely scenario is for the wet and windy conditions (gales, even perhaps severe gales) to lessen somewhat into the weekend, with an unsettled showery but still rather mild flavour to our weather prevailing into the midweek period thereafter... after which things will probably start to turn colder.

Crucially, there's a wide spread of pressure patterns developing in the model ensembles around that same time and so confidence on the type of weather we'll see remains low... for now.

However, the models are suggesting a steadily decreasing chance of heavier precipitation into that 10-15 day period. There's little signal in the current crop of supercomputer forecasts for significant snowfall at low levels and so on balance, the Met Office is suggesting we'll see some hill snow at times - initially in northern England and then progressively more widely - and some lighter outbreaks at lower levels at times (at least where southern districts are concerned).

It's of course an evolving story, but at the time of writing, dry(ish), cold (perhaps very cold) weather, with a likelihood of very hard frosts, seems the broader story into the 10-15 day period, but for at least the next 7 days or so we're expecting very much the opposite! 

So, never mind finding that ice scraper tomorrow morning - you'll be reaching for the brolly instead...

 

 

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