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: Dry Qualifying: Dry Race: Rain expected

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NOWCAST/FORECAST UPDATE: Sunday 06:00hrs BST: OK - here's the final forecast and it's essentially edging back more definitively to the thrust of our forecasts leading-up to today: wet running. It's much as we'd expected from the Met Office's Global Model, which held firm and was far more bullish on this, whilst some other models (notably the GFS) continued inter-run 'flipping' right to the last and 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 and - albeit dry right now at the circuit - current trajectories should see wet weather affecting it 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 https://www.nmc.gov.cn/publish/radar/shanghai.htm

Enjoy the race!

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Compared to steamy, showery Sepang a fortnight ago, it's a very different weather scenario forecast in Shanghai for 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 - and a nod towards the conditions likely to prevail at 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, with a range from possibly as low as 12-14C on Friday, peaking around 20-22C by Sunday, it's a notably cooler prospect challenging the teams compared 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 presenting a 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 a car-v-car dynamic we've yet to see, despite the 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 during most 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-fro and 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 afternoon remains elusive. The latest forecasts collectively emphasise a threat of showers at any stage of the race. However, 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, produced by the USA's NOAA, 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 sufficient variation to 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 China Meteorological Administration's medium-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 of forecast 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. What a nuisance...

The broad forecast theme is thus:

FRIDAY: I wouldn't be surprised if there's some generally low visibility around beneath a weak inversion by daybreak. Shanghai will lie beneath the ridge axis of an area of high pressure, drawing cool air off the Yellow Sea and some 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 however (and feeling that way too, with low relative humidity); perhaps up to around 16C given sufficient insolation by mid-afternoon (and probably closer to 12C for Practice 1). Track temperature will clearly be rather low, too - perhaps 25+C but certainly way, way below the values experienced at previous race weekends this season. Breezy at times, in the E-SE flow.

SATURDAY: The inversion is still fairly pronounced by dawn, so rather a murky, hazy start is likely again. With the ridge axis just starting to topple eastwards and a more southerly component to the prevailing flow, this - combined with higher (circa 14C) Theta-W air - suggests not as chilly a morning. Otherwise, it's a continuation of the dry story this time around - so no repeat of Sepang's memorable qualifying 'banana skins'! Pitwall radar screens should 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 the afternoon) and warmer at around 20C air temperature. Track temperature should readily recover to 25+C or so in these conditions. Wind predominantly SE and breezy at times.

SUNDAY: So here we go again then... if the latest modelling becomes reality, it's possible we'll see brollies on the grid again but probably not, this time, as sunshades!

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

Model runs from various forecast organisations tend (even at this rather late stage) to disagree on the rainfall distribution, accumulation and timing of eastward clearance. This rather poor continuity, both inter-run and between each model, has not been unusual. Nonethless, the combined ensemble collectively affords only moderate precision for the precipitation aspect of Sunday's forecast (at best) and I do stress this! Crucially, for example, one model offers a dry window effectively throughout the race. A real forecast headache, for sure. It'll go to the wire in terms of pinning this one down with higher confidence.

On balance though, the race does look likely to be rain affected at some stage, but just how wet (or not) might the prospects be? The teams will be very conscious of how much of the data assimilated through the dry practice and qualifying sessions could prove negated, come Sunday. If 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 circuit seeing 18-20C ambient. Aided by higher dewpoint air, higher partial thickness aloft and a 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.

Rather breezy again; winds from the south / SE.

More will follow!!