91Èȱ¬

It's only a quick blog this time, folks, as I'm away from tomorrow (Tuesday) for a fortnight and will resumeÌýa full F1 forecast blog just ahead of the next one in Monza, albeit probably online only by Thursday ahead of that race weekend...sorry for any inconvenience!

Well, it's the first time I've missed a live F1 event in some 13 years, so I'll be keeping well away from all newsmedia as I return to my underwater paradise to photograph yet more fish species on Red Sea reefs. I'll catch-up on all the (recorded) Spa weekend action immediatelyÌýwhen I return!

Broadscale Weather Prospects

It's always a risk publishing any sort of forecast this early and with no chance to modify it later, but hey, here goes!! But please do bear in mind this was written on Monday, so much is likely to change between now and the cars taking to the track on Friday morning. If I can offer any useful update from Egypt.... I will try!

It's been aÌýrather divergentÌýforecast evolutionÌýacross the model runsÌýuntil theÌýlast 12hrs, since when some semblance of consensus has emerged between the main operational centres concerning the Fri-Sun period and probable outcome at Spa.

We always hear (albeit often used incorrectly and vaguely) about the 'microclimate' at this track but the reality is thatÌýlocal conditions are inevitably dictated by the mesoscale situation, with nuances in this part of the ArdennesÌýthen dictatedÌýthrough varied orographic influences. In other words, pretty much the same story and forecast headache encounteredÌýin any heavily-wooded uplands across the globe.

This weekend will be no different.

It's a wet and breezyÌýspell loomingÌýinto Thursday (Spa has a 35 chance of seeing rain over 20mm, via a vigorousÌýAtlantic low, transiting eastwards, which will bring inclement weather to the UK during Wednesday). Therafter, high pressure will attempt to ridge eastwards into Belgium for Friday, but showery conditions will still dominate across much of northern France and into Benelux.

Although it could remain mostly dry, I wouldn't count on it!Ìý Showery outbreaks of (mostly light) rain are very likely, not least forcedÌýthrough orographic influences.ÌýWorth noting that the UKMO's MOGREPS-15 mapping of rainfall probability exceeding 0.5mm offers the chance of rain across Spa as 60+% during Friday. So, I'd be surprised if the day stays entirely dry throughout.

Depending on which model you choose, it could beÌýdistinctlyÌýcool too - important to stress this factor; for example, ambient temperature via the UKMO Global Model isÌýonly 15C. Brrrr!!!

I'm expecting Saturday to beÌýa fairly decent affair; some sunny spells; the anticyclonic ridging ever more influential but so mostly dry weather probable,Ìýbut withÌýa chance of a light shower forced-up again by the higher ground especially. So again, no guarantee of entirely dry conditions into FP3 and qualifying, but a pretty good chance for this outcome.

I haven't seen the ECMWF-EPS 00z output this morning (I'm about to leave!), but the latest from them (12z OP)Ìýshows the probability of rainfall at Spa on Saturday exceeding 1mmÌý(in the 24hr period)Ìýas greater than 35% but less thanÌý65%, so a reduced risk whenÌýcompared to Friday.Ìý

The localised detail will clearly remain the key issue as we approach Friday onwards. Sorry I won't be around to add this crucialÌýnowcastÌýstuffÌýfor you all, but I hope the rainfall radar, latest observationsÌýand other links I'veÌýlisted above will provide some help!

Sunday isÌýa trickyÌýone, and the latest output I'd seen from ECMWF and UKMO are largely nowÌýin line with other operational centres, notably GFS and Canada's GM.

All the centres agree on a firm mid-Atlantic block established by the high cell, with a depression set to skirt-down across the North Sea and swing frontal rain into parts of NW Europe, although any extension of thisÌýthreat southwards into Belgium will be tricky to call at this juncture. It could well bring a few light showers and patchy outbreaks of rain into Spa-Francorchamps as the race is underway, but crucially....

....EC, UKMOÌýand GFS have the low development and attendant precipitation further to the north and east, into Holland, Denmark and N Germany,Ìýwhilst mostly dry, ridged conditions prevail into Spa for Sunday with variable cloud cover.Ìý

As things stand, I'm more tempted by dry or mostly dry conditions on race day... but there's plenty of time for things to change (and you will all see the final result in real-time; I'll have to record it and watch later!)