Archives for June 2010

Current Forecast Emphasis (Latest update: Sat. 26 June, 21:50hrs BST)

As indicated in my previous forecasts, Glastonbury 2010 continues on a settled and hot note for Saturday and Sunday. Dry weather has prevailed since last weekend at Pilton and the parched ground is now set to remain underfoot until the end of the festival.

Overnight temperatures at Worthy Farm will remain very comfortable between now and Sunday: by dawn, falling to low double figures (10-12C). It'll stay dry and settled nocturnally between now and Sunday night, with some local mistiness by dawn.

The Glastonbury forecast offers this type of fine, settled and very warm weather into the weekend, with just a very small chance of showers (Photo: Matt Cardy / Getty Images)

High pollen counts and - as you'd expect - high UV levels will remain a feature into Sunday's fine weather.

It will continue the dry, largely sunny and very warm theme experienced on Saturday, as a southerly drift up into the British Isles keeps temperatures high across all of southern England. Much as we saw on Saturday, expect a maximum by mid to late afternoon around 26-28C, with a very low chance (<10%) of showers. So, it's very likely that Glastonbury 2010 will enjoy dry, fine conditions right through to it's conclusion.

And how I wish I was there to see Stevie Wonder - my muscial hero (and his brilliant bassman, Nathan Watts... will he also be on stage? Please let me know!).

Enjoy - and thanks to all of you who have been visiting the blog this past week.

Daily Summary:

WEDNESDAY: Dry, very warm and sunny. Max temp. 25C. Wind light SW

THURSDAY: Rather cloudy, misty start. Sunny spells then developing; small chance of a light shower. Humid feel. Max temp. 22C. Wind light WNW

FRIDAY: Early mist quickly clearing; sunny, dry and warm. Max temp. 25C. Wind light-moderate WNW.

SATURDAY: Sunny and very warm / hot. Chance of showers very low (<10%). Max temp 28C. Wind light WSW.

SUNDAY: Sunny and very warm / hot. Chance of showers very low (<10%). Max temp 28C. Wind light SSE.

MONDAY: Sunny spells and very warm.Max temp. 26C. Wind light W.

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Quick Links:

BBC Weather Glastonbury Forecast summary

Rainfall Radar (with zoom function, via MeteoGroup)

Visible Satellite Loop (EUMETSAT/DWD via sat24.com)

Live Webcams (via BBC)

Glastonbury Festival official website

BBC Glastonbury Festival website (includes TV/Radio schedules)

BBC Somerset: local news / travel updates / links to local & regional radio & TV

Valencia, 25-27 June 2010 (Round 9)

(This forecast will be regularly updated. This entry: Sunday 27 June, 11:50hrs BST)

Quick Links:

• BBC Sport: Formula One
• BBC Weather: Valencia Forecast
• Regional Rainfall Radar (via Agencia Estatal de Meteorología)
• Visible Satellite Loop (EUMETSAT/DWD via sat24.com)

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Nowcast Updates:

Sun. 12:55BST: Increasing cloud from the south, courtesty of the feature edging north (described below). Along the Costa Blanca south of Valencia (Benidorm and environs), it's now producing some isolated showers coastally and somewhat inland.Still worth keeping an eye on these developments albeit main thrust of any PPN remains offshore edging NNE.

Sun. 11:50BST: A dry, fine start in Valencia today, albeit the cumulus clouds forming in skies above the circuit are offering a hint of increasing mid-level destabilization. It's because to the south, an area of forcing moving northwards is producing a thundery cluster presently developing offshore through the Catalon Sea into Ibiza (very evident on satellite - see link above). It's recently showing signs of further convective developments up through the Costa Blanca itself. The main thrust takes a NNE trajectory just offshore away from Valencia and so any risk of showers still remains small (as noted in previous updates) through the race window. Nonetheless, it's worth keeping a eye of the satellite / radar links above....certainly can't offer a cast-iron guarantee of totally dry weather this afternoon, albeit this remains highly probable for the race itself.

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Forecast Headlines:

(PPN = Precipitation)

Friday: Sunny; chance of PPN 35%. Max 26C. Winds moderate ESE.

Saturday: Sunny; chance of PPN 30%. Max 26C. Winds moderate ESE.

Sunday: Sunny; chance of PPN 35%. Max 26C. Winds moderate, SE. 

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Fernando Alonso tackles the Valencia street circuit in the Renault during 2009's event. After a strong showing in Montreal, he's upbeat about his chances for this year's European GP in the Ferrari. Dry, sunny weather will prevail (Photo: AP / Alberto Saiz)

Synopsis and Forecast Emphasis:

After rather dull races for the past two years, I'm sure many fans would crave for a spell of wet running to enliven the spectacle at Valencia's street circuit. If so, you might well be disappointed with this weekend's forecast...

However, I think this year's race could well prove a good deal better in any case - not least given the tight level of competitiveness we've witnessed in some very compelling races this season.

Dry or mostly dry conditions are expected across Valencia each day for this year's event, with a low (typically <40%) collective chance of showers from Friday to the end of Sunday. A thermal low has developed across peninsular Spain, delivering some hefty showers and thunderstorms inland where they'll continue as the weekend progresses. However, the precipitation signal from various model ensembles remains fairly low for Mediterranean coastal districts of Spain and similarly across Valencia itself. So albeit showers are possible, they're unlikely.

Each day will see some very warm conditions in periods of strong sunshine as temperatures readily climb to the mid to high 20's C and track temperatures doubtless way up into mid 40'sC+. Winds will remain mostly light during the morning, but with moderate sea breezes then developing into the afternoon.

In turn, these sea breezes could - if conditions are favourable - offer a convergence zone 'strip' inland where some towering cumulus clouds will tend to grow and offer an increased shower potential by evening. It's not impossible that some evening and overnight showers could appear over Valencia, albeit this remains a low point probability.

The UK Met Office's MOGREPS ensemble modelling has offered around a 40% chance of precipitation (effectively as light showers) at some stage across Valencia and environs during the weekend, with greatest focus on Friday and Saturday. Spanish probability of precipitation (PoP) models are in agreement, offering a collective rainfall chance around 15-40%, peaking on Friday and with the driest signal for Sunday. The GFS ensemble also paints an essentially low rainfall probability. All the NWP products agree on keeping the greatest shower potential a good deal further inland, especially into northern-central parts of Spain. Early Friday morning, some showers have been skirting towards the Costa del Sol as a small area of forcing migrates northeastwards; this will tend to offer some convective developments into parts of the Costa Blanca later and still a small potential for showers.

UPDATE: Wednesday 16 June, 19:00hrs BST:
It's rare that I'd want a forecast to be wrong, but the events unfolding in France have, tragically, matched our worst expectations and represent the extremely dangerous conditions anticipated in the entry I'd written on Tuesday afternoon (below).

With torrential rain and resultant flash flooding proving a major hazard, at least 19 people have been confirmed as losing their lives in the appauling weather endured across parts of southern France. It's not the end of this particular event, so further perilous conditions are expected for another 24hrs or so, including across parts of France, northern Spain, northern Italy and the Alpine region.

Our BBC News Online link here gives an update on the situation as of now, as does - graphically - the video below.

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(Original Entry from Tuesday follows)

It's looking highly likely that a spell of exceptionally nasty weather will affect some parts of Europe over the next 48 hours (Tuesday-Thursday).

Through parts of southern France, northern Italy and across a swathe of the Alpine region, the stage is set for a genuinely extreme event, with rainfall expected to reach some 200 to 300mm throughout the period across much of this area. It's by no means impossible that some districts could see a deluge eventually totalling a staggering 500mm (half a metre).

Either way, those sorts of rainfall accumulations, over a fairly short period of time and across terrain with steep run-offs into river catchments, are bound to lead to some very dangerous and newsworthy conditions.

So why is this happening?

As I write, there's a strong upper vortex drifting down through the southern Bay of Biscay and rotating eastwards across northern Spain. In the next 24hrs, it'll swing northeast into southern France and towards the Alpine region.

Coupled to this upper air process, a plume of some very warm air, originating across North Africa, is advecting northwards. During Wednesday, it will engage with the upper vortex across the NW Mediterranean and into adjacent areas of southern France and northern Italy - a very potent cocktail, from which we'll see the generation of heavy rainfall and a threat of severe thunderstorms.

The Met Office synoptic chart (below) for midnight (GMT) Tuesday night into Wednesday illustrates the complex surface dynamics at play.

Some very heavy rain is already starting to feed north off the Mediterranean and affect parts of France, including near the likes of Nice and Monaco. You can keep an eye on this developing situation through this link to a composite loop of European rainfall radar.

Montreal, 11-13 June 2010 (Round 8)

(This forecast will be regularly updated. This entry: Sunday 13 June, 15:30hrs BST)

Quick Links:

• BBC Sport: Formula One
• BBC Weather: Montreal Forecast
• Local Rainfall Radar (via Environment Canada)
• Visible Satellite Loop (via Environment Canada

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Current Forecast Headlines:

(PPN = Precipitation)

Emphasis: No significant change from last update.Dry or mostly dry race expected with low % chance of isolated showers during the afternoon, especially later.

NOWCAST UPDATE: Note McGill (Montreal) radar is currently tending to pick-up spurious light-rate returns with no ground truth observations to support falling PPN at this stage. Some small isolated showers are, however, forming further west and NW, as evidenced periodically on the feed from Landrienne radar.

Friday: O'cast; a few sunny spells; chance of PPN 10%. Max 22C. Winds light SW.

Saturday: Rain clearing AM; chance of PPN later, 30%. Max 23C. Winds moderate, ENE.

Sunday: Partly cloudy with sunny spells; chance of PPN 30%. Max 25C. Winds light, E. 

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I noticed a comment written on a web forum, regarding the last race weekend forecast in Turkey:

"It's easy: Sunny and dry," this person wrote. "....so why bother with forecasts when it's just so obviously going to stay dry?"

Well, it may have seemed that way, but the 'very small risk of showers' highlighted in my blog that day was added because not all the forecast models were so bullish on keeping things 100% dry.

Indeed, during the race, a towering Cumulus congestus cloud - and associated moderate shower - formed close to the circuit. As it happened, it was the only one within a radius of many miles, but proved just how tricky offering this sort of site-specific forecast detail can be! It's all the tougher, of course, when forecasting ahead for a local weather window of only a mere couple of hours.

So, let's see how well the forecasts square with reality this time around! Off we travel to the fantastic Circuit Gilles Villeneuve in Montreal, thankfully reinstated to this year's race calendar after an absence in 2009 - the first time it had been dropped since 1987. It's a race that has often become something of a Safety Car showcase and equally, one where inclement weather has proved an important component in the track action here on the Île Notre-Dame.

Forecast emphasis and synoptic evolution

Summary: Although much of southern and midwest USA will be enduring increasingly hot temperatures later this week, Montreal will see maxima remain closer to seasonal norms, or slightly above into the weekend.

A far less less progressive advance of very warm conditions up into Canada has been the solution favoured by two models (ECMWF and UKMO-GM) all week. Both keep the heat ridge away to the SW and the (US) GFS model, originally far more bullish in heating things up, has now drifted into better agreement. Expectations are thus for temperatures to range into the mid 20's C through Friday-Sunday, with increasing humidity during the weekend, too.

As a fairly weak ridge of high pressure develops through Thursday night from Hudson Bay southeast to the eastern seabord of the USA, the prospects for Friday's on-track action during Free Practice 1 and 2 look rather cloudy but dry after what could be a rather foggy start in some districts around Montreal and the St Lawrence valley.

However, as the upper level WNW flow then establishes and persists into the weekend, we'll see a threat of more disturbed conditions being fed eastwards through Ontario, Wisconsin and other districts adjacent to the Great Lakes.

US NOAA-NWS rainfall accumulation prediction, above, for Saturday is indicative of potential for rain during the morning and showers during free practice 3 & qualifying in Montreal (red dot).

Saturday heralds an increased threat of wet weather, enhanced collectively in output over the past 48hrs from the model ensemble. Rain associated with a frontal boundary edges southeastwards through Ontario and Quebec this morning, as it runs through Montreal and south across the US border into Vermont and environs. This will wash the circuit back to 'green' conditions. Thereafter, it's all about the condions left in it's wake. High-resolution precipitation modelling today from NOAA-NWS suggests the rain clears southwards ahead of FP3, with a few showers then just about possible into the afternoon, coupled to some brighter spells slowly developing.

In a rather complex sandwich on Sunday, high pressure is building to the north around Hudson bay; an upper trough sinking southwards from east-central Canada; a quasi-stationary warm front sitting much further south; and a low pressure system approaching eastwards over the northern Great Lakes later during the day, swept-up within the prevailing flow around the high pressure to the north of Montreal.

Cloud will tend to increase steadily during the day as the influence of the approaching low becomes more evident. For the most part, there's a general lack of major forcing (e./g., absence of nearby frontal influences). The threat of rain will increase overnight and into a distinctly soggy looking spell through Monday.

So, a low chance of showers this afternoon. I anticipate the 'centre of gravity' for the threat of deeper convection to be held further southwards / westwards.

Dry weather looks the statistical likely outcome for the race, with Probability of Precipitation (PoP) predictive model solutions still ranging 30 to 40%. With increasing cloud, some of the model output maximum temperatures (into high 20's) look a tad optimistic; so we can shave a degree or two off these and offer a likely TMax this afternoon around 25C. 

Current forecast confidence for Friday's dry and settled theme is high; high for Saturday's potential for mixed weather and high for Sunday's mostly dry conditions and small chance of showers.

Alongside his many credentials as a skilled orator, the US President has now added a timely dose of weather wisdom to his portfolio.

I was duly impressed.

Yesterday afternoon (Monday) - in torrential rain and with lightning striking close by - Barack Obama attempted to start his Memorial Day speech, to huge crowds gathered at the Abraham Lincoln National Cemetery in Elwood, Illinois, some 50 miles south of Chicago.

With a severe thunderstorm booming directly overhead; squally winds from the storm's downdraft tugged at the President's large umbrella. Standing at the lecturn, the President immediately outlined a clear and present danger.

"We are a little bit concerned about lightning... this may not be safe," he told the thousands listening. "A little bit of rain doesn't hurt anybody, but we don't want anybody being struck by lightning." 

Urging everyone to return to their cars (and they're amongst the safest places to seek shelter in a thunderstorm), he was absoluely right to call proceedings to a halt.

In such circumstances, crowds standing close together in an open, exposed location, in wet clothes, is a recipe for lightning injury or fatality. In previous similar circumstances, multiple casualties have occurred simultaneously - including at soccer matches, affecting both players and spectactors alike. As well as direct cloud-to-ground strikes to humans, lightning can side-flash off stadium structures, trees and such-like to injure or kill people. Closer to home, we've seen some decidedly hazardous conditions from thunderstorms at the Glastonbury Festival in June 2005, for example.

Lightning is a major weather peril across the USA, something President Obama will have been acutely aware of as he called-off his speech. In fact, there's a Lightning Safety Awareness Week being held across Illinois later in June.

Indeed, in most years it causes more deaths there than hurricanes or tornados: typically, some 60 people are killed across the nation each year, with some 600 injured. Florida sees the highest number of casualties and in an average lifetime of 80 years, a US citizen has an estimated 1/6250 chance of being hit by lightning. However, only 10% of those struck are killed: 90% survive, albeit often with some form of disability.

Back here in the UK, we're entering the period when thunderstorms tend to become most prevalent, as the transitional and often very variable phase of cooler to warmer conditions experienced in May leads (we hope!) into summer. 

I'm concerned at the lack of lightning-savvy, reckless or extremely foolhardy behaviour sometimes seen in our country as threatening weather looms. For example, people continuing to shelter beneath trees during electrical storms; or insisting on playing a final round on a golf course; or continuing a hill-walking excursion towards a rain-lashed peak as thunder rumbles all around. In a later blog this summer, I'll expand on some of these safety issues and examine the statistics nationally for lightning-related deaths and injuries.

Meantime, in my BBC forecasts here, I am always at pains to highlight any threat of thunderstorms. However, I always talk of the "risk of lightning", rather than the "risk of thunder" I hear mentioned in some forecasts.

Yes, there have been some injuries and fatalities caused by thunder in the direct sense (e.g., riders suddenly dismounted by startled horses), but lightning is the potent threat (then resulting in the thunder), not the other way around!

I've seen first-hand, while working with Hertfordshire Fire & Rescue Service back in the 1990's, just how devastating lightning can be to people and property. I've witnessed major property fires resulting from it; house roofs virtually blown to smithereens; an entire herd of cattle killed overnight and on one occasion, we even had two of our firefighters struck.

They were hit simultaneously as they worked to extinguish a rooftop fire on a house north of Watford and were extremely fortunate to avoid major injury. Oh - and the cause of the fire they were tackling? A lightning strike, just a short time earlier...so much for "lightning never strikes twice", just one element in a broad spectrum of lightning-related mythology!

Have you ever experienced lightning strikes to your home, or even to you, your family or friends? I'd be fascinated to hear your stories in the blog comments section below.