03jtrickey

I'm surprised there's no guess the maximum sustained wind speed and gust competition yet...

Typical - wait all summer for storms at uni in Oxford...nothing! When I'm finally home in Cheltenham, we miss out by a few miles and Oxford gets them!

It's improving now, good section on D Day forecasting..

Agreed. Cringe!

Just watching it now...a slightly embarrassing opening...I don't know why they needed to dumb down the warm and cold fronts and jet streams to angry rugby players... it seems a little bit condescending! Anyhow, I will keep watching and hopefully it will improve!

It's been cloudy in Oxford since late morning, although it's very humid. The Netweather Extra radar showed a band of rain passing over, but only a few specs have fallen, not even enough to wet the ground. There is fairly thick cloud but whatever is showing on the radar isn't reaching ground level. I'm wondering whether the more intense stuff off the coast of Wales will continue eastwards across the country and intensify as it does so? Any thoughts on this?

I've just found the most surreal image from one of the Jamcams near Stoke-on-Trent of a herd of cows crossing a bridge during a thunderstorm!

Lots of cumulus bubbling up in Oxford at the moment and I'm liking the forecast for London & SE England from the Met Office: "A mostly sunny start before rather more cloud develops. Some areas will stay dry throughout. However scattered showers are expected to develop, with a few of these heavy and perhaps thundery over inland parts of the west, especially Oxfordshire. Maximum temperature 21 °C."

I'm in Oxford :-D Expecting that to hit us in the next 30-45 mins or so... but I'm wondering whether it's still electrified. Any reports from underneath it?

The storm near Salisbury looks pretty epic on the radar! Any updates from that area? Here's a useful lightning detector site that gets data from the Met Office... someone posted it on here a few days ago: http://andvari.vedur.is/athuganir/eldingar/i_dag_na.html?

Sister in Cheltenham says there's lightning, though no rain as yet.

Good luck to all the people back home in fair Cheltenham (& Gloucestershire)!! I think you may well be in with a chance of seeing something soon...shame Oxford will probably end up just too far east for the action.

Anyone else from Oxford here? Disappointing today... looks like we'll get away without any storms! Unless something pops up later or moves over from the west....

According to my girlfriend there was heavy rain, thunder and lightning in Sevenoaks earlier... she is now in Penshurst and looking at the radar could get rained on again fairly soon. More interesting than here in Oxford, at least at the moment. I'm hoping to see some more convection later! Not a whole lot at the moment where I am.

Thanks very much for your help

Hi, I have just started the Climatology section of my Geography course. I am struggling to understand the distinction between conditional instability and convective instability and I was wondering if anyone would be able to help me out. As I understand it, convective instability occurs when a layer of air which is more humid at the bottom than at the top, is lifted(by something - perhaps a cold front or a mountain range?). The bottom of the layer cools more slowly (briefly at DALR, then at the slower SALR) than the top of the layer which simply cools at the DALR. The temperature gradient increases and the layer becomes unstable and may overturn. I understand conditional instability to be when the lapse rate of an unsaturated layer of air lies between the saturated and dry adiabatic lapse rates. Therefore if a parcel of air from the layer is somehow lifted, when it reaches the lifting condensation level and becomes saturated, it will begin to cool more slowly at the SALR, and may rise above the environmental temperature (at the level of free convection) and will continue rising because it is less dense than surrounding air. However, I am finding it hard to see the difference between the two. Both types of instability seem to require the air to be lifted in some way (it is not very clear how). Is the difference about scale? (i.e. does convective instability occur only when a whole layer is forced up, whereas conditional instability is just a parcel being forced up?) Or does conditional instability only occur when the environmental temperature profile is right, whereas convective instability will always occur is a layer of moist to dry air is forced up? Another question that I had is - does convection occur with both types of instability? - it is a little confusing that one type is called convective but surely convective scenarios occur under conditional instability as well? Sorry for all the questions... I would really appreciate it if someone could help me understand these concepts better and I hope it is possible to make sense of what I have written!

89mph, Belmullet

Yes thanks for your detailed feedback, John. It certainly seems a very difficult subject, but now I have at least a reasonable explanation, without going into the detailed science and maths! With all those parameters consider it's incredible that computers can model and predict the weather. I'll see if can get a hold of that book sometime.

Thanks for your really helpful reply! That makes a lot of sense. So, in general, you need tigher isobars to produce the same wind speeds at higher latitudes. I found another site here with some details: http://www.tpub.com/weather2/7-9.htm And now I know what the Geostrophic wind scale is for on the synoptic charts! http://gliding.eusu.ed.ac.uk/met/syn.jpg What I'm still not quite sure about now is why latitude affects the wind speed. I've been trying to find out online and in "Atmosphere, Weather and Climate" but it seems extremely complex and I can't find a definitive answer! What is it that makes winds less strong at higher latitudes for a given pressure gradient?

Thanks for this Nick... that explains the high pressure. I wonder if there is a definitive explanation for the relatively low winds considering the tight gradient etc. :o

I was browsing through this morning's 06Z GFS run and noticed that at +168 (well into FI I know), there is a really strong pressure gradient showing around Greenland. I've spotted this phenomenon on many occasions before but it only just occurred to me that - if the isobars are so tight - why aren't the winds really strong? The NA Wind map for the same time shows winds of "just" 40-44mph over Greenland, while simultaneously over Ireland, similarly-spaced (perhaps even less tight) isobars produce wind speeds into the high 60s mph. Is there a reason for this? Perhaps because in Greenland the isobars are surrounding an area of HP whereas the winds over Ireland are from LP? Don't isobars of the same tightness always produce the same wind speed? Or does the Coriolis effect make the winds stronger to the RHS of an Atlantic low pressure system? Perhaps it is just because near Ireland the winds are over open sea? But even so the wind does not look as strong as I would have expected given how packed the isobars are near Greenland.

That's some seriously intense rain over the S Wales valleys!

I don't know about Pat and Jane - but I'm here. From Gloucestershire :-) Watching this morning's activity with interest although I was thinking the stuff over Wales might skirt north of here?

Fantastic news - should get some decent storms in Oklahoma! Celebrating last night? I'm glad I went out, although at one point I thought I'd be too tired - I hardly slept either! Such a relief to have the results and know what's happening with the next three years of my life.

I haven't been following the weather very intently recently, because it hasn't been all that interesting. But where did all this potential come from? This sounds exciting and I hope the potential is realised :-D