Weather charts part II

[Tugmistress]

ok, as suggested by kas, how i try to get a forecast for temp/rain and wind.

this'll look scary at first glance but it's not, if you followed the last thread this'll be a doddle ! (the pics on the old thread i have deleted but the whole thing is available on my site here if you want to recap)

i use 3 charts for this, the wind taken from the '500' charts, the temp taken from the '850' charts and the rain/cloud cover taken from the '500 - 1000' charts.

i'll post these in that order so you can see (hopefully) my train of thought.

Wind


Temp


Cloud



ok to start find our location on the map for wind, we are between the 1010mb and 1015mb isobars..... the gap is quite large so probably around 10mph winds (sustained) maybe the odd gust to around 15mph.... the direction of the wind? remember i said around a low the wind travels anti-clockwise and around a high clockwise? well this chart is a good one for you to look for which it is ..... the wind will always travel between isobars so it's either going to be southerly or northerly, which do you think it is? and how did you come to that conclusion? i'll edit this post tomorrow and give the answer, but if you want to have an educated guess then feel free to either pm me or post on here.... and i'll explain why too.

on to the temp....
first things first search for our location again lol.
you'll see a scale on the right of the chart - i don't use this i find it doesn't really tally with my thoughts lol.
we are in the yellow - yay- warmer than now! lol anyhow ....
there is a solid black line that separates the colours green from yellow, this line is 0c, the lines then turned dotted, the next one in to the green is -5c and the next one in to the yellow/orange range is the +5c - these are NOT temps on the ground but the temperature of the air at whatever height it is (not sure as don't need to know lol).
if you split the gaps down between the 0c line and the +5c line that we are located in, i would guess we are at about +0.5c on this chart. i have found that dependant on cloud cover a generalisation of add on 7-8c for daylight which is what we are dealing with as we are looking at noon next saturday 31st jan) will give the surface temp around here. we don't have any drastic geological features such as high mountains or deep valleys that will fluctuate and need a different way of working, i find this works for me in most forecasts i have been asked by various people to do.... now you see why i added a third chart of cloud cover!

cloud cover on this chart is easy to work out, white is cloud, black is clear skies lol. you can see that above us there is the faintest of cloud cover, so it should be fairly bright next saturday lunch with this high cloud that the sun should be able to shine through. the more cloud cover during the day, the less the sun will heat up the atmosphere, the less cloud cover the more it will heat up.... so looking at this i would add the 8c to the +0.5c 'area' that we are in from the previous chart, so temp at noon on 31st jan should be around 9c.


ok, any takers for the question posed? what direction will the wind be on this chart for caithness? and how did you come to that conclusion?

answer will be posted here tomorrow.

[2little2late]

[QUOTE
ok, any takers for the question posed? what direction will the wind be on this chart for caithness? and how did you come to that conclusion?

answer will be posted here tomorrow.[/QUOTE]

I would say the wind will be from a Northerly direction.
I reckon from the profile of the Isobars (If that's what they are). As the wind is blowing from the North the Isobars are quite elongated and as the cooler temp. meets the warmer temp. from the South they get closer thus creating the high pressure.

[Tugmistress]

I would say the wind will be from a Northerly direction.
I reckon from the profile of the Isobars (If that's what they are). As the wind is blowing from the North the Isobars are quite elongated and as the cooler temp. meets the warmer temp. from the South they get closer thus creating the high pressure.

I can understand your thoughts but unfortunately not quite right.
Look at the low in the first chart above that is off to the west of Ireland, the wind circulates anti-clockwise around this low, follow the isobars out and you will see the wind on this chart coming over caithness will be from a southerly direction.

Nice try though and quite a plausible thought.

[Tugmistress]

Day 2

Wind


Quite a large diference between yesterday and today in this chart, the low is centred a lot further to the south now and the 'loose low' that yesterday was situated NNW of the major low has increased in intensity slightly and also pushed it's way south and east and is now sat on the west coast of ireland, this has the effect of squeezing the isobars (lines) tighter together making the wind stronger, probably around the 20mph gusting to 30mph again from a mainly southerly or south south east direction.


Temp


We are just right underneath the 0c line, so working on my generalisation of adding 7 or 8c, without looking at cloud cover yet that's a prelimary temperature for this chart for us.

Cloud

This chart, although differing from yesterday, still gives a fairly clear sky above us so without cloud to hold the suns heat off, i will ask you to put your thoughts as to what the temperature according to this chart will be?

you can now see how the charts can sometimes change quite a bit in just 24hrs.

anyone up for a guess on temps according to these charts today?
again answer tomorrow evening.

[kas]

Cheers, I only got here and missed the question, I will have a good read through all this now. Thanks again.

[Tugmistress]

i don't know why the pics are not showing in the above thread i'll try to post them again then do tonights charts.

[Tugmistress]

Day 3

wind


Big difference here again, isobars (lines) are spreading out again, wind around 20mph maximum for us, the two lows off the west of ireland yesterday are now in different places again. it's gone more southerly still too.

temp


although the chart has a few changes, for us in caithness, it's about the same as yesterday so 7 or 8c before looking at the cloud cover.

cloud


Slightly more cloud around on this chart for us, so a reduction in temp, looking about 7c maximum i think.

todays question - why does cloud cover affect temperatures?

[Tugmistress]

day 4

wind


temp


cloud


you're now seeing very little change in the charts, things are as they were yesterday, so the forecast stands.
so, from 3 days away the forecasts are pretty much accurate, but you can see from any further they are very variable and extremely subject to change.

[wifie]

Sorry Tugs heid has been mince last few day so I have not been able to concentrate to try to answer. I have had a read today tho and am catching on (I think)! Promise to have a go next time!

[Tugmistress]

ok the results, temp i was right on, cloud cover was correct, i was a little low on my estimate of wind speed but direction was good.

temp today was max of 6.9c
cloud cover allowed a brief sign of the sun
wind speed 10 minute average about 30mph
direction southeasterly

[highlander]

Thank you for explaining the charts i am going to have to sit down and really study them, took me long enough to find britain with all the squiggly lines lol (should have put my glasses on lol). Ok heres my wee question, i have been flicking back and fore from BBC weather, they say no snow for us, sky weather says yes snow for us, can you tell us are we in for a lot of snow or just this cold cold wind. Thanks tuggs.

[Tugmistress]

Hi highlander.

the upper air temp in my limited experience has to be -7c or below for snow to definately fall here. looking at the charts this evening we have this temp above us from sunday midnight through til about 3am tuesday morning, so anything falling from the sky should be snow in theory. tuesday we have air of about 0c above us which will just produce rain if anything falls out of the sky. looking at the charts for the cloud for our 'snow' time, i don't think we'll get a lot if any, but i've also noticed since i moved up that the best snowfall round here is always the first half of march so far. January has been very lean with snow for me up here.