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Post by Deleted on Jul 16, 2014 9:15:47 GMT
Just a heads up for weekend, I get weather up dates from the met office and this is the latest one for anyone planning anything this weekend. if it saves anyone getting caught out then all the better. Those of you who keep tabs on the TV weather broadcasts will already be aware that the situation is getting more ‘interesting’ as we head towards the weekend, with an incursion of increasingly warm, humid air from the south Thursday in to Friday, followed by the almost predictable ‘thundery breakdown’ Friday in to Saturday. In terms of getting the detail right things are still far from certain and the details below will no doubt change as the event draws nearer. Nevertheless the first Met Office Alert has now been issued and it is appropriate to begin raising awareness to the possibility of disruption that might result. Although the Alert itself covers developments on Saturday, considered the most likely day for disruptive downpour/thunderstorm activity, the risk of some heavy, thundery downpours is also present on Friday when some minor impacts are possible. However, the level of uncertainty in the timing and location of any impacts from Friday’s showers means that we remain, for the time being, in green territory on the warning risk matrix. Friday incidentally looks like being the warmest day when maxima could reach the mid to upper 20s Celsius in places making it the warmest day of the year thus far. Through the course of Saturday some more widespread areas of thundery rain are expected to transfer slowly northwards across the UK. To cover the effects of these a Yellow Alert is now in force for the whole of Northwest England (very low likelihood of some significant impacts), valid from 0300 to 2400. The full text of the Alert can be digested either on the Met Office website or via Hazard Manager. The main threat is likely to come from surface water flooding due to localised areas of very heavy or even torrential rain. Lightning may also pose an additional risk, as we saw during the July 23 storms last year when railway signalling on parts of the network was affected. The flooding risk is discussed in detail in this morning’s Flood Guidance Statement to which I refer you, all of the region being shaded yellow (low flood risk) on Saturday. By the time we reach Sunday things should be quietening down as the atmosphere returns to a less ‘energetic’ state. Stay safe out there everyone!
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Post by Deleted on Jul 16, 2014 9:19:37 GMT
Cheers al. This site might be useful to some for flood warnings/river levels. gaugemap.co.uk/
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Post by r0b1et on Jul 16, 2014 10:18:08 GMT
Being a meteorologist I may as well jump in!
Thundery outbreaks are remarkably difficult to predict more than they will happen. Timing and location are incredibly sensitive to the smallest changes, so the warning area is likely to remain very large.
From the models etc I've seen it looks likely Friday evening/afternoon will have some heavy/thundery showers and Saturday will get warm/humid enough to really kick off. At this point how that will trigger will be far from certain, reading the warnings etc. the forecasters seem to think it is likely to be organised banded thnderstorms rather than scattered "pimples".
Keep an eye on the radar if you are planning a ride, the nature of thunderstorms means it's unlikely to be raining all day - but there could be a LOT of rain when it does happen.
<gets prepared to reapply his media hat>
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Post by Deleted on Jul 16, 2014 11:37:39 GMT
It was interesting to see my Accuweather app giving me a 'yellow warning for rain' for Saturday morning but the warning started early this week. I actually just ignored it assuming the Weathers been too good for anything nasty like that/too early to predict etc but I guess now it's looking likely. I was planning a long one early am Saturday morning but I think I'll bring it forward to Thursday now.
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Post by demonkarlos on Jul 16, 2014 11:39:41 GMT
I've got my first Triathlon this weekend. Open water swim too...
lovely.
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Post by stevo on Jul 16, 2014 12:41:59 GMT
A meteorologist once told me that they could 99% precisely forecast the weather for 6 hours and 95% for 24 hours and that after that, the preciseness percentage falls well below 50%. Don't know how true that is, but I can't remember a weekends weather checked on a Monday being very precise for some time now!!
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Post by ChrisD on Jul 16, 2014 13:02:55 GMT
I've got my first Triathlon this weekend. Open water swim too... lovely. You might e nd up with three open water swims...
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Post by r0b1et on Jul 16, 2014 13:23:35 GMT
A meteorologist once told me that they could 99% precisely forecast the weather for 6 hours and 95% for 24 hours and that after that, the preciseness percentage falls well below 50%. Don't know how true that is, but I can't remember a weekends weather checked on a Monday being very precise for some time now!! Probably more relevant is how long ago they said that - since I've been in meteorology things have got a LOT better. And precision is largely irrelevant, I assume you want accuracy. But 99%/95%/50% of what? by what measure? If "what will the pressure be", these days a week out we are well into the 90%s. If it's how much rain will there be on my house a week out on a showery day then It'll be very poor. Summer is definitely not the strong point as convection is difficult to predict... remember the winter storms where you got 5 days warning for each and every one with incredible accuracy and often precision too. That kind of weather is pressure dominated so easier to predict... it is more deterministic.
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Post by Deleted on Jul 16, 2014 13:24:42 GMT
I've got my first Triathlon this weekend. Open water swim too... lovely. Good luck with it. My lad is doing the UK Ironman in the Bolton area on Sunday. Should be interesting. He said he would rather have rain than it being hot and dehydrating.
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Post by Deleted on Jul 16, 2014 13:50:34 GMT
Another update,
No overall change to yesterday’s opening briefing on developments during the coming few days with increasingly warm, humid conditions spreading northwards from tomorrow, temperatures peaking on Friday (27 or 28C possible in the south of the region) with the main threat of disruptive rain and thunderstorms reserved for Saturday. Yesterday’s Yellow Alert for Saturday has been re-issued (again including the whole of the Northwest) with a risk rating again of Yellow but with the likelihood of significant impacts raised from very low to low, reflecting some increase in confidence that within the very large area at risk we are more likely to see significant impacts than we were this time yesterday. Today’s Flood Guidance Statement has all of the Northwest at Yellow (low flood risk) on Saturday, the area at risk map on page 2 confirming the flood risk as a combination of surface water excess from localised intense rainfall and the possibility that such rainfall will result in overspill from small, urban water courses or other fast-responding river catchments. The severe weather Alert and Flood Guidance Statement can be viewed via the usual sources, be it Hazard Manager (both) or the Met Office website (Alert only). Looking at things in a bit more detail and first Friday, when the main risk of any disruption looks like being early in the day. Overnight Thursday into Friday an initial pulse of thundery rain is expected to slide up the western side of the UK. How far east it extends is open to considerable doubt at present but there is a chance that it could clip the more western parts of the region early in the day giving a few sharp, possibly thundery bursts of rain, before moving off again, leaving the rest of Friday dry with some sunshine and increasingly warm/humid. Confidence in this feature is insufficient as yet to merit an Alert but it’s something worth keeping in mind for the time being. On Friday evening and overnight the main threat of disruptive rain/thunderstorms will emerge from France and begin its journey northwards across the UK. The main uncertainty here is the western extent of this area of potentially disruptive weather which could well include the whole of our region but which could end up further to the east with less impact on the Northwest. It will probably take until Friday afternoon until we know for sure what degree of exposure the Northwest will have to this threat which will include flooding as outlined above and possible lightning-related impacts. The main risk period for us appears to be from midnight until around 1800 Saturday, after which the worst of any rain should have largely moved off to the north. Sunday will see slightly less humid conditions but still the potential for showers which could themselves turn locally heavy and thundery, albeit probably not as intense as some of the rain that falls over the UK during Saturday. One inevitable consequence of the warmth and humidity will be high nocturnal temperatures (typically 14 to 17C tomorrow night and 16 to 19C on Friday night), a good time to bring out the fans to relieve the stuffiness a little.
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Post by jimc on Jul 16, 2014 14:08:10 GMT
Being a meteorologist I may as well jump in!... The B'TWIN RBOC, the only bike owners club with their own weatherman!
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Post by Steph on Jul 16, 2014 18:44:05 GMT
Bah. Hope Sunday is Ok, planning a 100k ride for a Strava challenge
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Post by Deleted on Jul 17, 2014 10:25:07 GMT
Another up date.
The picture for Friday and Saturday is a little clearer than was the case 24 hours ago, however there remains a good deal of uncertainty regarding developments going into Saturday. Below is a summary of the main points as they currently stand.
· Still the risk of a shower, possibly heavy/thundery, clipping the west of the region later tonight and early tomorrow, most likely Cheshire/Merseyside. However, any impacts should be minor and no warnings will be issued in association with these. Breezy too during this period with fresh to strong easterlies possible over exposed locations, easing through Friday morning.
· For most tomorrow – a dry day with some patchy cloud but sunny spells will raise temperatures to their highest levels of the summer so far, perhaps as high as 28/29C in Cheshire/Greater Manchester and nearer 25-27C over Cumbria, still just below Heat Health Watch thresholds for Northwest England but hot all the same and with uncomfortably high humidity. Very isolated thunderstorms possible late afternoon/early evening, mainly hills Cumbria/Pennines. Were one to go off there could be localised torrential rain/frequent lightning and a short notice warning may be required. Too much uncertainty at present to merit a warning but worth keeping an occasional eye on the radar through tomorrow afternoon. Very warm, uncomfortable, close night tomorrow with minima in the range 16-20C.
· The main risk of disruptive rain/thunderstorms comes after midnight tomorrow night and through Saturday daytime (as per yesterday’s briefing). All eyes will be focussed on areas of locally intense thundery rain drifting up from the south. Our region looks as likely as anywhere now to catch one or more of these storms but the finer detail remains elusive at this point in time, i.e. we can’t yet specify the exact timing, location and intensity of the activity. Outdoor events taking place on Saturday could well be adversely affected, as will be, no doubt, transport through the region. The main threat of disruption will come primarily from surface water flooding but also possibly from lightning strikes affecting power networks etc. In such a situation such as this there will inevitably be a need to keep monitoring the radar rainfall in order to keep tabs on developments. High-energy weather situations like these are amongst the most challenging for our weather forecast models with the detail prone to subtle changes from one update to the next. Top temperatures on Saturday back in the low 20s Celsius but still very humid.
· Yesterday’s Yellow Alert for Saturday will be re-issued this morning, covering a wide swathe of the UK and again including the whole of the Northwest. The risk matrix tick remains in the Low Likelihood of Significant Impacts box for today but may be upgraded to Amber tomorrow if a clearer picture emerges of those areas at greatest risk. This morning’s Flood Guidance Statement gives a full description of the Flood Risk across the Northwest (Yellow, Low) in association with Saturday’s developments, again emphasising the risk from i) surface water flooding due to short-period high-intensity rainfall and ii) river flooding from small/narrow urban watercourses or other rapid responding catchments.
· Heavy rain/thunderstorm activity tending to ease as we move into Saturday evening, Sunday a slightly fresher day, still with the risk of some sharp showers going off by the afternoon but not of the intensity of those liable to affect us on Saturday, hence no warnings in force for Sunday.
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