Bodhi

I have just seen the wind obs map on xcweather and notice that there are a number of places where winds are moving differently to synoptic patterns. Middle England shows divergence just in from the Weslh border and then reconvergence at the top of East Anglia. My location shows Westerlies, bending from a general SW flow- although slightly lower down the flow has turned Northward along the Aberdeenshire coast. Does anyone know if there is a book that gives all the different surface wind modifiers and how they interact, please? Cheers, Rich

Hi folks, Thank you for your replies. Firstly to Jo: Thanks. I'll look up the warm /cold advection. In answer to your question. I am eternally curious and a single question often leads me down a complex rabbit hole of further questions. I taught myself a lot of meteorology a few years back when learning bushcraft and survival skills. I thought it'd be great to be able to predict the weather in order to know when to build shelter early and organise different outdoor tasks. Recently I was out explaining bits and pieces to an interested party on things like natural navigation and weather front clouds, and this reinspired me to start regular sky watching again. Then I noticed these phenomena . I also saw, from the same position at a different time,low clouds following a curved path. Secondly to Nick: Thanks - I am about to check out those links after replying to you. OK its good to know that synoptic flow can also do this. I have a little more info on the situation after someone showed me the Kinloss METARs for the time period. Kinloss picked up the two winds at slightly different times. I'm guessing that a siungle station has no way of differentiating between one wind veering and two winds colliding necessarily. Ayway the METAR shows winds 200 veering to 280 and then 060. The 060 would make a shallow angle wind to the coast, coming in from the right- I am informed that this is indeed likely to be a sea breeze. Just as an aside my father was born and raised in South Norwood. Best wishes, Rich

Dear All, I just spent half an hour writing this post and when I sent it the forum had logged me out and the post was lost. I'll rewrite it but much more succintly as I'm low on time now. Thanks for any replies. 1) Local lower wind clouds colliding - one set from NW, the other from S. Neither a sea breeze. How is this possible and can I predict it via obs or charts? 2) Ac layer moving at approx 30 degrees to a lower Ac layer, that in turn was moving at almost ninety degrees to the low cloud. Is there any information oout there on the basic physics of this and an explanation? 3) Highest insolation, bith incident on atmosphere and at ground (Ahren's) at 30N in the n hemisphere. If the Hadlley cell is driven by thermal winds created near the equator and sending upper level wind polewards due to the gradients established, then why isnt 30N the uplift region for the hadley cell in summer when it has a higher insolation than the Equator. Why is it still the rough area for sinking air? I appreciate any help. Thanks. Rich

Hi Kev I am sorry that no-one has answered your question. I had lots of questions myself but the format of the forum seems to imply a greater knowledge base than exists in reality. I was hoping to have a detailed chat on many aspects of the weather here but so far a proper discussion thread has been elusive and I still have many areas needing clarification (like coriolis etc). Please take the following as the answers of a newbie so they may well contain errors. 1. I have seen troughs on charts that relate to an extension of a low pressure area. These are cyclonically curved kinks stretching away from the low....like a valley on an OS map . The other troughs on the met maps are black lines of potentially bad weather that show no clues on the surface pressure maps that I can see. The met map says these lines can also be upper air troughs or low thickness areas. 2. I would suspect that a trough (second defintion-black line on map ones) wouldnt move into another airmass generally because it woud have to pass through a front. It seems to be from map observation a phenomena that occurs within an air mass away from frontal surfaces. 3. http://www.stormtrack.org/forum/showthread.php?14683-Plotting-Fronts. Perhaps also a useful forum I would add that while its not necessarily a good way to plot fronts they are visible on some fo the satellite pics I have seen. I hope to have helped somewhat. All the best Rich

Makes a nice change to be sitting in dry NE Scotland watching you all having snow! My son works in HB so its good to be able to rag him about this too Any more pics as you taken some lovely images there? All the best Rich

Enjoy!

Nice

Hi Lorenzo. Yes, they might be I guess but the flight paths aren't usually that close- normally you get one or two far away- but could be. I wonder why they do this swirling pattern thogh then. Hi WS. What makes you say that? They have the little elements (less than 1 deg across) and are pure white and look like the piccies in my book which is why I suggested this, but would like to hear why you think that. I think no 5 does have ragged cu in it, and the ci and the swirls were much higher I think. Cheers Rich PS great pic Lorenzo

The first two pictures I am thinking are altocumulus elements? (with Stratocumulus in the background in number 1) The second set of 5 were taken this morning. The pre dawn was light cirrostratus across the sky but negligable, only giveaway was the halo round the moon but no visible cloud. In the direction of these clouds "behind the trees" was thick altostratus. The temperature ahd dropped considerably leading me to expect frost and a stable atmosphere of more stratus types, which proved true, until at about 10:30 am these appeared. Usually the mountains will kick up lenticular formations of vatrying clarity above and behind that tree line, but never seen these before..cirrocumulus in swirls? Be interested to hear some opinions. Cheers Rich

The MET map showed a stationary front turning into a cold front today and passing over the UK. Tomorrow it reverses and becomes a warm front and crosses back (at least it shows it doing so up here in North Scotland). It seems it'll then come back over again if the forecast is right. Firstly I'd like to find out if this happens often and secondly is the reason for the mild frontal weather to do with the stable middle to high pressures? If so on the second question and wind is generally coming down how come I have seen a very thick cloud cover (altostratus with lower sc and scuds)? Cheers Rich

took this at sunset

Yes, I think I agree. The only thing that bothered me was that this morning I was looking at how lenticular clouds form and they shouldnt move much due to that whereas some of these do travel. I also was reading about Stratocumulus lenticularis the other day and these clouds look like they might fit in with that with the higher alto stratus above.....I'd like to hear your thoughts Cheers and all the best RD Rich

Apart from wanting to share a stunning sky I would appreciate comments on the elements in these pictures in terms of formation etc. Cheers and all the best Rich

Hi FFO Thanks for replying. Yes, I agree that angular momentum wasn't taken into consideration. If we look at the formula for this we have: Angular Momentum = Iw where I is inertia and w is the angular velocity. This also equals mvr where m is the mass, v is the instantenous velocity (or general speed if you like) and r is the radius. Given that m will be the same for the air parcel at the equator and all the way up through the SN trajectory we can see that to conserve angular momentum we will need to increase v as r decreases. If we take r at the equator to be 6372km and, by my calc, the earths surface speed at that point to be 463ms-1 we get the following speed increases at the following latitudes: 20N 492ms-1 45N 655ms-1 62N 986ms-1 85N 5316ms-1 Two points: The spin speed increase is still only proportional to the EW beginning velocity and so still unaffected in the NS direction (ie the angular momentum is all at 90degrees to the NS intial velocity). The velocity at 85N would require a centripetal acceleration of 51ms-2 to hold it in place. Even if gravity were fully acting in the direction of centripetal acceleration (which it is not by a huge margin) it could only provide just under 10ms-2 of that 51. As it happens it has such a weak centripetal component at 85N that it is hugely under 1ms-2. Ie the air parcel would fly off into space......... For the coriolis effect the angular momentum conservation isn't going to solve it. I did these calculations before looking at the (kindly provided) web address and nothing I have said in this post contradicts the sites very good explanation. So we are still needing a reason for the NS velocity to affect the EW component and increase curvature when we fire a shot (or move an air parcel) due North.... Back to you Cheers and all the best Rich

Firstly thank you FFO for continuing with this thread. I still don't think we have a definite answer here unfortunately. Why? I am with you for your initial points until "Big Problem" The compensation for an object travelling north from the equator to an observer on the ground would seem to just be based on its EW velocity picked up at the equator from where it started. This compensation is a direct one that relates not to the objects NS velocity but only to its EW component. This compensation is fixed irrespective of the NS therefore. The coriolis force is non-intuitive it seems and probably does require the maths to explain it I am thinking.... The pdf is good but again assumes the coriolis effect. Is there no simple step by step explanation of the coriolis term on the net, as I can't find anything that doesn't give me a headache! Cheers Rich