The Novice's Chart Thread

[tugmistress]

well we definately only had rain today and very windy still from that chart. they are starting to make a little sense to me now.

going to give it another shot on one random chart after i have had my tea .... that's if you don't mind?

[tugmistress]

ok sorry for the delay, i have just been backing up my site as the hosts have really peed me off this time they changed permissions on me again, the second time in 6 weeks which destroys 99% of the images on my site and i can't get into the admin side

anyway, back on topic, going to make a fool of myself here again, but tell me where i go wrong please.

am only using these charts as i am not on the NWextra

from the first one i can see it is going to warmer in the yellow area than the green probably temps around 6 to 10c maybe even as high as 13c in the yellow bits. it is going to be windy as the middle of the low is sat over somewhere near the A66 going past OON (btw my geography is rubbish here) and the isobars are reasonably close together but not all over. if the wind goes anti clockwise around a low, then the south will have wind from the west (ish) the east will have wind from the south (ish) the north will have wind from the east (ish) and the west will have wind from the north (ish).

the second just tells me it is going to persist it down over most of the country so wet & windy!

third one just tells me that the the wind is going to be worst where it is red lol.

getting worse huuh?

[Thundery wintry showers]

Yes, you're clearly getting the hang of this now- that's a pretty accurate synopsis of what the charts are telling us.

[tugmistress]

tahnks TWS,

just been in the 12z discussion reading that... didn't realise i had picked a chart that people where talking about sorry so no i didn't see that lot before ... honest!

[Thundery wintry showers]

I didn't think you had been 'cheating' by browsing the 12Z discussion and copying off it- I could tell by the way the post was worded.

[tugmistress]

lol, cheers TWS:D

didn't think you would but thought i had better say it before someone did think it

even reading through the 12z i don't know i would have understood some of it but i am getting there, i will just have to eat a dictionary for pudding after my pizza

[Stoxs]

lol, cheers TWS:D

didn't think you would but thought i had better say it before someone did think it

even reading through the 12z i don't know i would have understood some of it but i am getting there, i will just have to eat a dictionary for pudding after my pizza

hey tug you are certainlly getting the hang of this now i am at a bout the same stage as you i think and i am finding difficulty in see the wobbles in the isobars that gives unstable air i.e ppn i tiny little wiggle seams to be about 2 inchs of rain a bit confussing any way i will leave you to keep posting your charts and i will study the results and when the tutors come round and mark you i can see where you went wrong well done

[Coopsy]

Would somebody be able to help me out?

I was out last night and the temp was -30oC and the sky was clear but in the air there were tiny clear ice crystals. Is this due to the air freezing as it looked like someone had thrown glitter in front of me?

It definately wasnt snow

I would be grateful if someone can confirm if this can happen at -30oC because it was an amazing sight

Thanks

[Paul]

I'm not totally sure of the answer, but my guess would be that it was the moisture on your breath freezing as it hit the cold air? On top of this if it were wider ranging than just in front of you, the chances are it was the moisture in the air freezing, although at that temp I can't imagine there would have been much!!!

[Coopsy]

I'm not totally sure of the answer, but my guess would be that it was the moisture on your breath freezing as it hit the cold air? On top of this if it were wider ranging than just in front of you, the chances are it was the moisture in the air freezing, although at that temp I can't imagine there would have been much!!!

Thanks for that Paul. It was both whilst I was in a car and outside. I saw it in the head lights of the car and then when I was outside it was in front of me so it could have been both. I dont think it was snow/ice crytsals being blown around as there was no wind last night either.

My initial thoughts were moisture in the air freezing. It was impressive though but didnt like the fact that my nose froze everytime I breathed in

[JohnAcc]

Would somebody be able to help me out?

I was out last night and the temp was -30oC and the sky was clear but in the air there were tiny clear ice crystals. Is this due to the air freezing as it looked like someone had thrown glitter in front of me?

It definately wasnt snow

I would be grateful if someone can confirm if this can happen at -30oC because it was an amazing sight

Thanks

Hi Canadiancoops,

Ice crystals can form under clear skies and light winds as the temp drops. As they flutter downward they can glitter in the sun or moon light and are commonly called 'diamond dust'.

I think they form at temps below -18C as hexagonal plates and or columns.

[Coopsy]

Hi Canadiancoops,

Ice crystals can form under clear skies and light winds as the temp drops. As they flutter downward they can glitter in the sun or moon light and are commonly called 'diamond dust'.

I think they form at temps below -18C as hexagonal plates and or columns.

Thanks, that explains what I saw. I thought i was seeing things at first. It looked exactly what frost does, just in the air

[I can't believe it's not better]

Looking at the basic GFS chart viewer and in particular the 3hr PPN output. I've noticed that areas of ppn grow and shrink in intensity for each 3 hour step. eg. low intensity at 0z, high intensity at 3z, low intensity at 6z, ... and so on.

Could anyone tell me whats going on? Cheers.

[devon lad]

Looking at the basic GFS chart viewer and in particular the 3hr PPN output. I've noticed that areas of ppn grow and shrink in intensity for each 3 hour step. eg. low intensity at 0z, high intensity at 3z, low intensity at 6z, ... and so on.

Could anyone tell me whats going on? Cheers.

Hi ICBINT

PPN can alter dramatically in a very short space of time whether it is frontal or convective due to many reasons.

The comment I really want to make is that on a thread for newbies (see 1st post) they may not understand acronyms like GFS, PPN, Oz etc .... did you when you first came on site.

Not to say your observation is not valid.

Regards.

dl

[Thundersquall]

Here's a chart from tonight's run. What I see now is that the colours represent where the air is cold enough to snow AT 500HPA (or 18,000feet)

Apparently, 528dam(or less) means snow is possible. Look at the bar on the right. Turquoise, Blue Pink and Purple are 528 or less. So any area one of those colours has a chance of snow AT THAT ALTITUDE:

So 528 dam means an area has a chance of snow only if it's 5280 metres high? Remember these are DecAMetres, hence DAM.

Edited December 3, 2005 by Thundersquall

[I can't believe it's not better]

Hi ICBINT

PPN can alter dramatically in a very short space of time whether it is frontal or convective due to many reasons.

The comment I really want to make is that on a thread for newbies (see 1st post) they may not understand acronyms like GFS, PPN, Oz etc .... did you when you first came on site.

Not to say your observation is not valid.

Regards.

dl

Some of the acronyms, but generally I've had to look them up. Plenty I still don't know, but getting there Had more trouble learning general online chat-room acronyms tbh.

[devon lad]

Some of the acronyms, but generally I've had to look them up. Plenty I still don't know, but getting there Had more trouble learning general online chat-room acronyms tbh.

Good answer!

Plain English is a rare art these days.

dl

[BrickFielder]

Looking at the basic GFS chart viewer and in particular the 3hr PPN output. I've noticed that areas of ppn grow and shrink in intensity for each 3 hour step. eg. low intensity at 0z, high intensity at 3z, low intensity at 6z, ... and so on.

Could anyone tell me whats going on? Cheers.

Yes I have noticed it has a tendency to do that sometimes. Rainfall can be affected by heating from the sun and warmer or dryer air moving in at mid levels. What I think you are refering to is that rain is light at 3pm, heavy at 6pm ,then light at 9pm and heavy again at middnight with no obvious reason. The answer is I don't know and it could be a problem with that particular chart or GFS or just an unusual occurance.

[BrickFielder]

So 528 dam means an area has a chance of snow only if it's 5280 metres high? Remember these are DecAMetres, hence DAM.

5280 metres is the height in the atmosphere that pressure is 500hPa. It gives an indication of what the pressure is at low levels. The point is that it tells you something about what is happening midway up in the atmosphere and can be used as a rough guide to what is happening at low levels.

528DAM and below for an increasing chance of seeing snowfall, preferable values of 522 and below.

546DAM tends to be associated with the mild and wet conditions in winter - so isn't very popular! In the summer this line is usually close to the northwest of the country.

564DAM and above is usually found with a very warm airmass in summer, and most often in a Spanish plume affair. Very warm or hot conditions are likely.

Usually we don't see much above 570DAM or much below 515DAM in the UK.

[I can't believe it's not better]

Yes I have noticed it has a tendency to do that sometimes. Rainfall can be affected by heating from the sun and warmer or dryer air moving in at mid levels. What I think you are refering to is that rain is light at 3pm, heavy at 6pm ,then light at 9pm and heavy again at middnight with no obvious reason. The answer is I don't know and it could be a problem with that particular chart or GFS or just an unusual occurance.

I'll keep an eye on it and let you know if it gets worse.

[Daisy]

Hi all,

A complete newbie who knows nothing I am afraid but I am interested in learning more. Its very addictive!

I tried posting this on another thread but was totally ignored . I guess everyone else was too interested in the charts to be bothered answering what to them is probably a silly question, but you've got to start somewhere....

I wonder if any of you intelligent folk could explain to me what an outlier is? I see it all the time in the replies on the forum and wasn't sure what it refers to on the charts. I was wondering if it was a "rogue" event that looked like it was going to happen then didn't, or whether it was a finger-like projection on the charts showing much milder or colder air, or something else entirely!

If anyone could help explain that would be great :lol:

regards

D

[Paul]

Hi Daisy, have a look in this thread, you'll find the answer there :lol:

http://www.net-weather.co.uk/forum/index.php?showtopic=23720

[BrickFielder]

When the GFS forecasting models run at midnight ,6am midday and 6pm a number of runs are performed, each with slightly different criteria. This means that there are a number of forecasts with slightly different outcomes. One of these forecasts is picked as the actual one. If the picked forecast is generally colder or warmer than the others then it is considered an outlier. The temperatures it forecast are outside the normal of the other runs and is considered more unlikely. We tell if a run is an outlier by looking at the ensembles which show the temperatures forecast on all the runs. Generally outliers are unlikely to be acurate forecasts, but what might be an outlier in one place (i.e. London) may not somewhere else (i.e. Aberdeen). In other words if a forecast is an outlier take it with a pinch of salt. Far too often a forecast is pronounced an outlier just because people do not like what is forecast.

[J10]

http://www.net-weather.co.uk/index.cgi?act...c23c93593c5bc54

[Daisy]

When the GFS forecasting models run at midnight ,6am midday and 6pm a number of runs are performed, each with slightly different criteria. This means that there are a number of forecasts with slightly different outcomes. One of these forecasts is picked as the actual one. If the picked forecast is generally colder or warmer than the others then it is considered an outlier. The temperatures it forecast are outside the normal of the other runs and is considered more unlikely. We tell if a run is an outlier by looking at the ensembles which show the temperatures forecast on all the runs. Generally outliers are unlikely to be acurate forecasts, but what might be an outlier in one place (i.e. London) may not somewhere else (i.e. Aberdeen). In other words if a forecast is an outlier take it with a pinch of salt. Far too often a forecast is pronounced an outlier just because people do not like what is forecast.

Thanks very much for help. The thread was useful too, I'm not sure I have understood it all yet. I need to keep reading and going over it. It would be great if there was a night class I could go to. This weather stuff is getting me hooked! I'll be having my own weather station next! :lol:

D