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Yeongam,Ìý22 -Ìý24ÌýOctober 2010 (Round 17)

(This forecast will be regularly updated. This entry: FridayÌý22 October, 18:40hrs BST)

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ÌýForecast Summary:

(PPN = Precipitation)

Emphasis:ÌýHigh confidence for dry Friday; Saturday's FP3/Quali sessions alsoÌýexpected to remain dry. Improving inter-model continuityÌýsuggests aÌýthreat of rain arriving into Sunday, with increasing potential to affect the race.

Friday:ÌýCONFIDENCE HIGH: Sunny spells and dry. Chance of PPN 5%. Max 22C.Ìý Breezy at times. Wind ENE.

Saturday: CONFIDENCE HIGH: Turning cloudier during the day. Rather breezy again. Expected to remain dry throughoutÌýFP3/Quali.ÌýÌýChance of PPN 30% until end of quali,Ìýbut rain arriving late evening / towards midnight. Max 21C. WindÌýENE.

Sunday:ÌýCONFIDENCE MODERATE (improving): Mostly cloudy. Rain expected to have arrived overnight, albeit heaviest PPN expectedÌýfurther to theÌýsouth. Possible that wet weather will have departed before race start, but this remains open to a high degree of uncertainty. Chance of PPN 70%. ÌýMax 19C. Breezy.Ìý Wind ENE.Ìý

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Synopsis & Forecast Evolution:

Update to original entry (below):

Friday Update, based on 12z Model runs:

There's closer agreement generally now between the main operational centres, with a high chance of rain falling across the circuit at some stage later Saturday and into Sunday. This has been strongly signalled for some timeÌýin the ECMWF-ENS output for Mokpo; ditto (with good continuity) by Canada's GM, the UKMO-GM, Japan's GM and (on and off) by NOGAPS. Korea's own KMA modelling and meteogram spreadÌýoffers a similar idea.

The US-GFS has tended to play catch-up of late, now bringing rain overnight Saturday and into Sunday morning, but clears it well ahead of race start. This solution has about 50% support and we'll see if the 00zÌýGFS (and other op centres)Ìýbuild on the theme of dry weather and / or onlyÌýlight showery outbreaks of rainÌýprevailing by the time the lights go out. Certainly not impossible, in my view.Ìý The Canadian model falls into a roughly similar camp, with fairly heavy overnight and morning rain trending much lighter ahead of race start.

Meanwhile, the Japanese, EC and UKMO modelling still threaten outbreaks of rain (some heavy)Ìýcontinuing into the race window. The Canadian output had alsoÌýdoggedly stuck to this idea virtually all week, with UKMO not far behind in terms of continuity and remaining so in the latest run. ECMWF's output is best summarised in a remark from the Met Office's Deputy Chief Forecaster made to me earlier today, who - afterÌýanalysing the Mokpo EP meteogram -Ìýconcluded: "....(there's) clearly a high chance for some heavy rain, either before the race, if not actually during it."

So it's a very finely balanced situation; further runs are needed to gauge continuity on the areal spread of heaviest rainfall and the timing of any clearance off eastwards.ÌýBroadly speaking, a middle ground approach is to anticipate rain arriving overnight and into the morning (= green track), mostly clearing away to the east before midday but with potential for some lighter showery outbreaks continuing for a while into the afternoon.

Thursday Update, based on 12z Model runs:

Today's ensembles maintain a trend - already offered with high forecast confidence some days agoÌý- for dry running to prevailÌýthroughout Friday's sessions and a strong prospect of the same outcome on Saturday. The focus of forecast attention remains very much fixed onÌýSunday, with a growing prospect of rain arriving during the day, courtesy of the ex-Megi remnants described in the original entry (below). As also highlighted below, this threat of wet weather has been consistently offered by some models as a minority to 50% solution, while the US-GFS - suffering some earlier upstream divergence in handling Megi's track - has continued to oscillate in solutions for Sunday.

Crucially however, it has tended toÌýerratically edgeÌýthe prospect of rain northwards in successive recent runs. It's 12zÌýoutput now comes into broader, if not exact,Ìýagreement with most other operational centres (ECMWF, UKMO, JMA, CMC, NOGAPSÌýetc.)Ìýby bringing a prospect of rain across the extreme SW and S districts of South Korea throughout Sunday. Other models are more bullish, with a more northerly, extensiveÌýthreat of rainÌýand in the case of CMC (exhibiting strong continuity), offering showersÌýpotentially slightly earlier from overnight Sat-Sun. The timing of this - plus precise degree of northerly extent of anyÌýprecipitation -Ìýwill be the critical factors during race day.Ìý

Clearly, tomorrow's runs will be important in terms of continuity (or lack thereof); CMC, UKMO and some others having already 'led the way' in threatening a wet or potentially wet race, with GFS tending to play catch-up in the last 24hrs. I'll update you all again tomorrow, by which time we'll have seen just how the teams fare on the new circuit in dry, fine conditions during FP1 and 2!

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(Original Entry follows)

While the Suzuka forecastÌýwas a (rare) example of great inter-model continuity andÌýbullish forecast confidence -Ìýeven quite a few days ahead of the event - assessing weather prospects at this inaugural Korean eventÌýhave beenÌýproving quite the opposite!

Forecast confidence is now starting to improve and consolidate. Currently, only the weather for Friday's practice sessions can be foretold with a very high degree of certainty:Ìýit's looking dry, fine and rather breezy for those. The various models are starting to show increasing agreement for the rest of the track action to stay dry, too.

Now, I hope you can keep up with this next bit - but it's pretty critical in determining just how dry (or not) the new and doubtless rather slick asphalt will remain by the end of the race weekend!

The complications emerge especially during Sunday, much of them courtesy of how extra-tropical remnants from Typhoon 15W, named 'Megi', track and evolve through the mid to latter parts of next week.

Right now, Megi - located SE of Hong Kong - is tracking very much as anticipated, steeredÌýaroundÌýthe southern boundary ofÌýa deep-layeredÌýmid-level subtropical ridge. WithÌýtime, the western portion ofÌýthat ridge of high pressure will subside due to mid-latitude influences coming east out of China, while the typhoon itselfÌýis expectedÌýto continue it's more poleward track.

Megi isÌýcurrently expected to make landfall into S.E. China / Hong Kong, according to the official model output from the .Ìý Therafter however, the complex evolution of the dissipating core - and extent and distribution of it's northward rainfall outflow - are all influenced by various factors, including a trough emergingÌýsouth-eastward through mid-central China. However, it will certainly dissipate and weaken as the poleward journey continues during the week,Ìýthrough theÌýincreasing influence of land and decreasing potency of vertical wind shear. But the northerly-orientatedÌýoutflow of rainfall and associated 'lobes' of low pressure will remain pretty noteworthy features on weather chartsÌýfor a few days still, some of this possibly crossing - or at least grazing -South Korea later during the race weekend. However, this is most likely to occur post-race andÌý overnight int Monday.

The main 'free' forecast model output available on the web, feeding many automated popular forecast websites, is the US-GFS model. Importantly, it has persisted in offering a divergent track in certain respects compared to the collective (and very similar)Ìýoutput of other dynamic models (e.g., ECMWF, UKMO, NOGAPS, GFDN). On the basis of consensual expert analysis, the GFS trackÌýyou might see on some weather websites is still presently considered the 'outlier' solution by the Joint TyphoonÌýWarning Center and is, in their words, "....deemed as unlikely,Ìýconsidering the strength and positionÌýof the steering subtropical ridge positioned to the north."Ìý

Consequently, the GFS forecast further 'downstream' into later stages of next week may prove somewhat unreliable for south Korea (at leastÌýat this range), albeit continuity in the broaderÌýweekend prospectsÌýfor Mokpo is now improving.

The UK Met Office and Canadian CMC modelsÌýwere both quite progressive in taking a threat of rain - some heavy - northward towards Korea into the weekend. Previous runs of UKMO suggested overnight wet weather Sat-Sun but unlikely to directly impact track sessions; CMC, meanwhile, offered a decidedly wet race.ÌýUKMO has now reverted to a dry solution for Saturday and Sunday, bringing the threat of rain only later during Sunday and into Monday. CMC, however, sticks to the notion of a very wet spell into and throughoutÌýthe race window. It remains effectively alone in this very pessimistic solution (but that doesn't mean it's to be discounted!).

GFS has exhibited some pretty typical oscillations at this sort of forecast range and especially in a complex set-up.ÌýÌýIt sticks to the idea of dry weather all weekend, steering any rainfall southwards across Japan.ÌýECMWF, meanwhile, is essentially the closest to the Megi 'official' track published by the Joint Typhoon Warning CenterÌýand also looks to keep the race weekend dry or largely so.

A reasoned summary, for now at least, suggests:

- dry, sunny & breezyÌýweather all of Friday;

- very probably dryÌý(and again breezy, plus eventually somewhat cloudier)Ìýconditions for Saturday's sessions, and

- a dry, breezy and fairly warm race the more likely outcome, but with an uncertain, lowÌý%Ìýthreat of rain appearing during the event.

I'll of course keep you updated all the way...

So, the weekend looks a benign affair for us here in the West Country: high pressure still the dominant theme; generally light winds, some sunny spellsÌýand remaining dry.

It'll be distinctly cool, however, with the potential for a widespread ground frost in our inland areas, overnight Saturday into Sunday.

In the next few days, I dare say some newspapers will start hyperventilating. Expect to readÌýaboutÌýan imminent "Arctic Blast!"; or how "Winter Arrives!", etc., etc.

Why?

Because early next week, we'll see a transition to a colder, unsettled cyclonic pattern which draws the prevailing flow directly down from the north, accompanied by brisk winds and a more showery regime of weather across the nation.

However...

The current Met Office prognosis is hardly forewarning ofÌý'Snowmageddon'.Ìý

Yes, we do expect to see some snow accumulation across the Scottish mountains next week; equally, there's a fair chance of transient (as opposed to lying, or disruptive) snow even fallingÌýto low levels for a while across other parts of Scotland and similarly, some districts of northern England.

The various forecast models inevitably vary in just how far south the cold 'plunge' is advected into England, but the prospects of any snow appearing further southwards are extremely limited. In fact, it looks barely worth a punt.

The broader theme will be a chilly, windy and occasionally showery spell of weather through a fair part of the next working week.

We can expect periodic bands of showers - someÌýlikely to be a tad lively,Ìýoffering hail and a crack or twoÌýof thunder - to arrive on the brisk and very noticeable northerly flow, but with brighter spells dominating between these, across most districts.

Beyond that, the latest Met Office longer term (i.e., in medium range) analysis keeps things somewhat on the cool side, but no early or widespread advent of winter weatherÌýin the true sense.

Best to keep the sledge tucked-away in the garage for now... but for sure, you can dust-off those warm coats and gloves!

Suzuka,Ìý8 -Ìý10ÌýOctober 2010 (Round 16)

(This forecast will be regularly updated. This entry: SaturdayÌý9 October, 21:05hrs BST)

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Quick Links:

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Nowcast / Forecast Updates:

Saturday, 2100BST: As per model expectations (and they've been excellent this weekend), the rain has now left the circuit by 0500 Local and I'm expecting a dry or largely dry scenario to now prevailÌýfor the rest of Sunday. Good news for qualifying, then! One or two light showers are still possible, but it's a low % point probability and the real hazard for drivers is straying off the asphalt and into very sodden run-offÌý / gravel trap areas. So, quali could still be a tricky affair! One wheel off the kerbs could spell disaster.

Saturday, 1150BST: So, the 'worst case scenario' alluded to in my forecast below - i.e., a potential for undriveable conditions during qualifying - unfortunately became reality. We'll see aÌýslow and rather erratic improvement in conditions for the rest of this evening andÌýtonight in Suzuka, but JMA weather advisories and warning currently remain in force, not least to cater for further heavy pulses of rain easing northwards along ripple or wave-like perturbations on the frontal zone. Areas of flooding, with landslip risk, are a real possibility in some parts of Mie Prefecture. The postponed qualifyingÌýon Sunday (10am local;Ìý0200BST)Ìýwill take place after the rain departs; current modelled estimates takeÌýit's back edge of away northwardsÌýfrom Mie by around 04-0600 local. The circuitÌýwill thus still be pretty tricky for qualifying - especially the sodden margins & run-offs - but steadily drying.Ìý We'll then see hints of the cloud deck breaking with some brighter spells developing progressively towards midday.ÌýDuring the qualifying window, there's still aÌý(small-ish) chance of a few light showers - these are catered for as a 30% chance of PPN by JMA's forecastersÌý(and with good inter-model support). The race, meanwhile, remains as previously forecast: dry, with brighter or sunny spells; much warmer and with a low (10%) prospect of any further showers.

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Forecast Summary:

(PPN = Precipitation)

Emphasis:ÌýUnsettled conditions developing PM & overnight Friday, bringing spells of heavy rainÌýSaturday, especially PM, continuing into Sunday AM. Inclement weather will have cleared well ahead of race start.

Friday:ÌýSunny spells; mostly dry but with a chance of a few showers later PM as cloud increases.Ìý Rain arriving through the late afternoon and overnight, heavy at times. Chance of PPN 30%. Max 24C. Wind light, SSE.

Saturday: Overcast and breezy, with outbreaks of rain throughout the day, turning heavy at times and especially during the afternoon and evening. Up to 50mm accumulation plausible. Continuing wet & rather windy overnight. Chance of PPN 90%. Max 21C. WindÌýfreshening / briskÌýSE.

Sunday:ÌýFurther outbreaks of rain throughÌýa cloudyÌýmorning, easing by mid-morning.ÌýDry and probably brighter by race start; i.e., a dampÌýcircuit then steadily drying(?).ÌýA few light showers still possible during early afternoon. Chance of PPN 80% AM; 20% PM. Max 25C. Wind moderating, predominantlyÌýNW.Ìý

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Synopsis & Forecast Evolution:

There's now broad inter-model consensusÌýfor a tropical low / wave-like depression to form off Taiwan during Thursday andÌýmove NNE towards Japan. The centre eventually tracks just offshore east of Honshu throughout the weekend and deepens, with an arm of the jetstream directly aloft -Ìýoffering significant potency and fluidity in the eventual degree / extentÌýof bad weather across Suzuka, especially throughout Saturday.

Currently, the most pessimistic solutions from major operational centres (e.g., Canadian CMC; UKMO, NOGAPS and to an extent, GFS) offer a very wetr propect for Qualifying. This is likely to prove the major point of weather-related interest / uncertainty in an already critical race weekend for the five championship protagonists.

Day-by-Day:

Whilst Friday has a pretty decent chance of dry running for P1 and P2, the onset of inclement conditions appear later into the evening and become dominantÌýduring Saturday.ÌýWithÌýFP3 and qualifying in mind, thisÌýwill be real concern for the teams.

As the low tracks north, it is likely to become very developmental across Okinawa during Saturday and with various wavelike / ripple perturbations running ahead (possibly formingÌýa secondary low centre)Ìýinto southern areas of Japan, offering a real potential for heavy showers, including across Mie Prefecture (and Suzuka, located therein).

All the models agree on some grim weather throughout Saturday and especially later in the day. As soil moisture deficit continues to shrink from later Friday onwards, substantial run-off and standing water could become a real issue around the circuit by Saturday.ÌýÌýTiming will be critical as the model continuity improves: i.e., will conditions possibly worsen ahead of qualifying, or after? It's more likely to be after... but impossible to call reliably until we see reality unfolding on radar.ÌýWith 50+mm rainfall accumulation notÌýout of the bounds of probability, there's obviously aÌýpossibility of undriveable (red-flagged) weather but this can be considered a fairly low risk. The worse conditions presentlyÌýlook set for the late afternoon and evening.

Either way, the low centre continues to look very threatening by 00GMT (0900hrs local)Ìýon Sunday morning but thankfully, it's impact on the actual race should then beÌýsteadily reducing.

In broadscale terms,Ìýthe low centre is likely to be located just offshore from Mie Prefecture during the early morningÌýand tracking NNE, if the currently fairly good inter-model agreement can be trusted.

The precipitation (and trailing cold front sitting off to the south) then ease off to the north quite quickly during Sunday morning, so the race itself will be dry or largely so. However, the earlier rain will have keptÌýthe circuitÌývery sodden during the morning and I'd imagine the margins / run-off areas / section beneath 130R crossover will remain treacherous!.

One possible complication towards the early afternoon is any degree of wrap-around occlusion debris swinging back from the north towards Mie,Ìý bringing a few light showers, especially with any sunny spells adding to daytime heating and instability. With this in mind, I've retained a 20% point probability of afternoon precipitation and I note the Japanese Meteorological Agency do likewise. However, it's very likely for this critical race to run entirely dry,Ìýwithout further weather interruption. Exactly what grid line-up we'll have by the end of Saturday might well haveÌýprovided more than enough weather drama, anyway!