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flyer

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  • Gender
    Male
  • Location
    chilbolton observatory (North Hampshire when home)
  • Interests
    Weather, Aviation, Sking, Serious diy !:)) and most importantly lamp post watching (not during mild weather though) oh and observing net weather bun fights.

    coldies rule !!!!!
  • Weather Preferences
    Good dump of snow or a damn good thunderstorm

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  1. Thats it I'm done on both sides now. Blowing like a goodun. Off back into my tent. Might be gone some time Nighty night.
  2. Evening all. Well morning all to those still up. Wind has arrived pretty much on que forecast as early Monday morning. Gusts have stepped up a notch and are pretty violent now having just gone on a garden walkabout. Eyes are on the ground so not sure how much longer I can hold out, bit of a lightweight Soon be snow watch ! Central North Hampshire.
  3. Apologies Konstantinos, I just looked at first glance at your figs half way down without realizing that you have taken the limits either side of a bearing so indeed they are correct. I have sent you a PM
  4. The accuracy will be better.This is simply because if the "actual" surface pressure is known then as others have mentioned the barometer responds logarithmically to give a defined pressure altitude at your location relative to the ground pressure BUT your reading would only be 100% accurate for a finite time depending on whether the atmospheric pressure is stable and the only way to keep it accurate when say hillwalking or flying is to get the actual updated ground pressure or as John Holmes stated to predict the changes using graphs.
  5. Hi Konstantinos From googling I have so far determined that at Athens airport the magnetic variation or otherwise known as declination as of 2008 was E 3°29.6' that is 3°29.6' East of True North but as you will know it changes continually by about 9' per year. So with the above reading True North will be 3°29.6 to the left of Magnetic North. In the UK the variation given is deemed to be reasonably accurate for purposes of duration of flight from East to West and presumably for Greece too as it is of the same sort of scale land mass wise. However if flying say in the United states from East to West over some 5000Km then the magnetic variation is quite considerable over distance. If you try Googling in Greece look for airport information which will hopefully somewhere give you the present variation . I think some or all GPS units might give the variation too. A flying version definitely does but using a real map gives you more insight into the effects. Your figures that you show are drifting a little. I have drawn you a (Corel Draw) picture on the attachment which makes things easy to see together with Athens Magnetic variation (2008) relative to True North.
  6. You could look at Wikipedia which tends to be very scientifically orientated but this link is much simpler http://www.flyingmag...altitude-pencil
  7. HI Konstantinos Here is an extract from the link I gave above " In meteorology, an azimuth of 000° is used only when no wind is blowing, while 360° means the wind is from the North." I am not a 100 % sure but in standard meteorology I believe it is relative to fixed North. In aviation meteorology winds are relative to Magnetic North, this is because a plane flies using a compass which will point to magnetic North and magnetic North is constantly changing (albeit slowly) due to the earths precipitation (wobble) relative to fixed North so to fly an accurate path your calculations are relative to the same datum which would be magnetic North. Just out of interest when aviation maps are updated they print the current position of magnetic North relative to true North and vary +/- by about 5 deg which you have to add or subtract from true North to get a relative bearing to true North to allow what your compass is telling you versus what the map measurement tells you. "When the direction is 30 degrees, we choose between NE(45 degrees) and ENE(22.5 degrees), right? So, we choose ENE because 30 - 22.5 < 45 - 30?" When direction is 30 deg it is between NNE which is 22.5 deg and NE which is 45 deg. Think of the circle as quadrants with you standing in the middle. Top right of circle 0 deg to 90 deg. Bottom right 90 deg to 180 deg. Bottom left 180 deg to 270 deg and Top Left 270 deg to 360 deg. So in your example the Top Right quadrant is the general direction that the wind is coming from. 30 deg is less than NE (which is 45 deg) so your wind more accurately is coming from somewhere between North (0 deg) and NE (45 deg) As 30 deg is MORE than the bearing in between which is a NNE (which is 22.5 deg) then it is somewhere between a NNE (22.5 deg) and a NE (which is 45 deg) So as 30 is NEARER to 22.5 deg than 45 deg it would be stated as a NNE. A further example : A wind bearing of say 280 deg. The wind is now coming(blowing) from somewhere in the Top Left quadrant. A West wind is at 270 deg and a North West wind is half way between a West and a North which is 315 deg (270 + 45 = 315) The bearing in between these two is 22.5 deg so you add 270 deg + 22.5 deg which gives 292.5 deg which is our WNW. Note again the first letter (W) tells us that the wind is biased towards the West bearing and is to the left of the North West bearing. In the example of our 280 deg bearing it is closer to 270 deg than to 292.5 deg (WNW) and so would be described as a WEST wind, that is blowing from the West towards you stood in the circle.
  8. Hi Konstantinos. This link (http://meteorologytr...ss/14269_55.htm) should help clear things up but in plain english the bearing given is the direction the wind is coming from relative to North. North can be termed both 0 deg and 360 deg. So for example imagine a plan view (that is you looking down on a circle) with you stood at the centre of the circle and North at the top then the main points will be East to your right. West to your left and South behind you. If a wind is stated as an Easterly then it is blowing from the East and is at 90 deg relative to North. If it is a southerly then it will be blowing at you from behind and will be at 180 deg relative to North. The next MAIN four points after N.S,E and W are NE (North East) , SE (South East), SW (South West) and NW (North West). These 4 points are each half way between the main N,S,E and W which would be better put in order as N,E,S and West as bearings tend to be measured in a clockwise manner by convention. So using the original example above with you stood in the middle of the circle facing North then a NE (North East) wind will be blowing FROM the North East (which would be half way between a North wind and an East wind) and would be at an angle of 45 deg relative to North. In contrast a wind shown as a SE ( South Easterly) would be blowing towards you (half way between an East wind and a South wind) and relative to North would have an angle of 135 deg (That is 90 deg of an Easterly + 45 deg = 135 deg total) The other two, SW and NW having relative bearings of 225 deg and 315 deg respectively relative to North. The Next set of bearings which make things more accurate are the points in between the 45 deg points just mentioned above so for example a NNE (North, North East) will be blowing from that direction towards the centre of the circle at an angle relative to North of 22.5 deg It should be noted that The first (letter) N in this case, is the bias that determines which side of the NE bearing you mean. So with that in mind the bearing the OTHER side of a NE would be an ENE noting the first E denoting the bias is towards the East. One more example, a SSW will be a bias towards the South and will be half way between a South wind and a South West wind so you will find the bearing relative to North to be 202.5 deg that is (180 deg + 22.5 deg) Just remember all wind directions given mean the direction the wind is blowing from, towards you stood in the middle of the circle facing North. Hope this helps.
  9. A few snow blasts here lasting 10 seconds at a time. Quite impressive to see. Looks to be a building cloud mass from the East so may get a covering.
  10. 100% snow now but pretty wet so no settling but nice to see. Good to see potential cold ahead if a snow fan although remains to be seen if us in the far south will be in the mix but with days like today never say never.
  11. 50% rain 50% snow here and folk coming down the road with a covering on the car roof so must be on the boundary. Temp 6 deg, bizarre as it's not exactly intense on the evap cooling side of things.
  12. Funny thing, got the sit on out today then realized I was out of petrol so trundled up the road to get some and noticed the temp gauge was showing 6 deg. Got back and was trundling round the garden grass cutting then a 5 min quite intense snow shower started up. Think the neighbours thought I was barking. Must admit it did seem kind of strange.
  13. Deffo "polly put the kettle on" stuff. It is snowing again in the heavier radar bursts.
  14. Classic, heavy snow just now settling well, temp dropped to 0.9 deg and now it's almost raining. DP unknown but guess it's on the up.
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