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Shanghai, 16-18 April 2010

(This forecast will be regularly updated. This entry: Sunday 18 April 2010, 06:00hrs BST)

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SUMMARY: Practice 1, 2, 3: ¶Ù°ù²âÌýÌý Qualifying: ¶Ù°ù²âÌýÌý Race:Ìý¸é²¹¾±²ÔÌý±ð³æ±è±ð³¦³Ù±ð»åÌý

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NOWCAST/FORECAST UPDATE: Sunday 06:00hrs BST: OK - here's the final forecast and it's essentially edging back more definitivelyÌýtoÌýthe thrust of our forecasts leading-up to today:Ìýwet running. It's much as we'd expected from the Met Office's Global Model, which held firm and was far more bullishÌýon this, whilst some other models (notably the GFS) continued inter-run 'flipping' right to the lastÌýand wanted to lessen the rain considerably. As noted a couple of days ago, this one was always going to go to the wire, forecast-wise!

Rain is now falling quite extensively west of Shanghai andÌý - albeit dry right now at the circuit - current trajectoriesÌýshould see wet weather affectingÌýit within the next hour or so with moderate rainfall rates and the odd heavier burst possible. It's then all about the showery nature of things: will we see intermittently dry or drier spells during the event? As they'll be doing on the pitwall - keep an eye on the local rainfall radar at

Enjoy the race!

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Compared to steamy, showery Sepang a fortnight ago,Ìýit's a very different weather scenario forecast in ShanghaiÌýfor the teams, drivers, spectators - and Eddie Jordan's shirts, assuming he arrives there after flight delays courtesy of the Icelandic volcanic ash cloud.

Because one very noteworthy aspect -Ìýand aÌýnod towards the conditions likely to prevailÌýat various European races - will be the temperature.

After a decidely cool start on Friday morning, the race weekend will see these gradually rise by Sunday. Nonetheless,Ìýwith a range from possibly as low as 12-14C on Friday, peakingÌýaround 20-22C by Sunday, it's a notably coolerÌýprospectÌýchallenging the teamsÌýcompared to Bahrain, Australia and Malaysia.

Indeed, it's shaping-up to be a little below average for this time of year in Shanghai (and worth noting the annual mean is 16C), but certainly presentingÌýa much more comfortable working environment in the pitlane! Whether it'll make tyre performance more comfortable for some teams is another matter altogether... and it's fascinating stuff. It's aÌýcar-v-car dynamic we've yet to see, despiteÌýthe rather cool but largely unrepresentative running experienced during winter testing.

During April, some 90-95mm of rain typically falls across the district of Jiading, where the circuit is located to the NW of Shanghai centre. The climate is classically sub-tropical maritime monsoon, but dry weather will prevail duringÌýmost periods of track action.

Note I said 'most'...

....because Race Day has a risk of some wet weather.

Broad model agreement, with very good continuity, offers dry weather across all the practice sessions and qualifying too (McLaren and Ferrari radar-watchers will breath a collective sigh of relief!).

Sunday, by contrast, has been subject to all manner of forecasting swings to-and-froÌýand will be a wholly different challenge. It's likely to be affected by some rain at times, although the finer hour-by-hour detail for the afternoonÌýremains elusive.ÌýThe latest forecastsÌýcollectively emphasise a threat of showers at any stage of the race.ÌýHowever, it's by no means a 'done deal', if you are after a wet spectacle! I expect the heaviest rain to arrive after the event finishes.

The GFS (Global Forecast System) model, , offers a snapshot of the inclement weather expected by Sunday early afternoon across eastern China. The oranges and greens represent rainfall, with a front close to Shanghai (arrowed, red) clearing slowly east.

One model (the USA's GFS) has tended to flip-flop the rainfall progression with sufficientÌývariationÌýto offer a very wet race on some previous runs, versus a more intermittently wet scenario on others. It continues to do this with almost every run of the supercomputer, seemingly struggling to handle the position and phasing of rainfall. The Ìýmedium-range mesoscale modelling; UK Met Office's Global Model; Canada's global model and forecast products from Taiwan and Korea all offer broad support for a threat of showers appearing during the day, but with varying degrees ofÌýforecast precipitation rate/accumulation and subtle differences in the areal spread and timing of wet weather. Some bring it by the morning; others only by late afternoon.Ìý What a nuisance...

The broad forecast theme is thus:

FRIDAY: I wouldn't be surprised if there's some generally low visibilityÌýaround beneath a weak Ìýby daybreak. Shanghai will lie beneath the ridge axis of an area ofÌýhigh pressure, drawing cool air off the Yellow Sea andÌýsome low-level moisture beneath dry, cold air aloft. As the day develops, it will remain dry with hazy sunsine. Comparatively cool ambient temperatures will be the most noteworthy feature howeverÌý(and feeling that way too, with low relative humidity);Ìýperhaps up to around 16C given sufficient insolation by mid-afternoonÌý(and probably closer to 12C for Practice 1).ÌýTrack temperature will clearly be rather low, too - perhaps 25+C but certainly way, way below the values experiencedÌýatÌýprevious race weekends this season. Breezy at times,Ìýin the E-SE flow.

SATURDAY: The inversion is still fairly pronounced by dawn, so rather a murky, hazyÌýstart is likely again. With the ridge axis just starting to topple eastwards and a more southerly component to theÌýprevailing flow, this - combined with higher (circa 14C)Ìý air - suggests not as chilly a morning. Otherwise, it's a continuation of the dry story this time around - so no repeat of Ìý Pitwall radar screensÌýshould be redundant on Saturday afternoon. Hazy sunshine should typify the scene at Shanghai; some high and medium-level veils of cloud (increasingly so later in theÌýafternoon)Ìýand warmerÌýat around 20C air temperature. Track temperatureÌýshould readily recover to 25+C or soÌýin these conditions. Wind predominantly SE and breezy at times.

SUNDAY:

Showers will start to make eastward progress into parts of eastern ChinaÌýthroughout the morning, turning to more persistent rain at times.

ModelÌýruns from various forecast organisations tend (even at this rather late stage)ÌýtoÌýdisagree onÌýthe rainfall distribution, accumulationÌýand timing of eastward clearance.ÌýThis rather poor continuity, both inter-run and between eachÌýmodel,Ìýhas notÌýbeenÌýunusual. Nonethless,Ìýthe combined ensembleÌýcollectivelyÌýaffords onlyÌýmoderate precision forÌýthe precipitation aspectÌýof Sunday's forecast (at best) and I do stress this! Crucially, for example, one model offers a dry window effectively throughout the race.ÌýA real forecast headache, for sure. It'll go to the wire in terms of pinning this one down with higher confidence.

On balance though,ÌýtheÌýrace does look likely to be rain affected at some stage, but just how wet (or not)Ìýmight the prospects be?ÌýThe teams will be very conscious of how much of theÌýdata assimilated through the dry practice and qualifying sessions could prove negated, come Sunday.ÌýIf the entire race runs dry (which is not wholly impossible), they'll be highly relieved. All eyes to those radars again, come Sunday...

A few brighter spells are possible but the largely overcast conditions will depress temperatures, with the circuitÌýseeing 18-20C ambient. Aided byÌý, higher ÌýandÌýa warmer southeasterly flow, it won't feel chilly - even with any leaden skies. I doubt track temperatures will reach much above 25-28C beneath the fairly extensive cloud cover.ÌýÌý

Rather breezy again; winds from the south / SE.

More will follow!!