The Novice's Chart Thread

[smich]

Glad this thread is of use to peeps

It's certainly helping me a lot.

Thanks to the forecasters for their guidance also - just a reminder to keep it stupid simple. For example, the Low goes over the top of the high pressure (the toppler) - is that "goes over" as in higher latitude, or "goes over" as in higher ALTITUDE?

I know it may seem silly, but never underestimate the stupidity of us newbies

!

Smich

[BrickFielder]

Latitude. Sort of like the diagrams below. High pressure topples over the Uk from the north.

[smich]

Latitude. Sort of like the diagrams below. High pressure topples over the Uk from the north.

Cheers BF! Your diagrams remind me of ...I can't quite place it....oh yes! The last 5 GFS runs!

Attention all novices! To see a Toppler in action, check out the latest GFS run!!

Mind you (and I know I'm only a novice), I am certain this mild scenario cannot last very long compared with recent years. I see Steve M's pics of the jet upstream and it looks very unstable to me. It's just a case of waiting a couple of weeks for the jet to shift, and the high will suddenly creep west into the atlantic and we will have another Northerly, slightly more potent than last month. I will go with 19th/20th before the cold comes our way, and if it stays for more than a week (which I think it might), we are looking at an unsettled and cold Xmas...

Blimey! I just did a forecast! I need to go and lie down for a bit...

Smich

[Daisy]

Thanks for that question about the toppler Smich, I assumed it went over the top in altitude

Certainly learning loads.

Cheers everyone

Daisy

[noggin]

I had asked a question re topplers but then found the answer in Brickfielder's illustration

I am so glad to have found this thread.....they don't come much more stupid than me. Silly thing is, I've always been absolutely fascinated by the weather, just never understood how it works .

Edited December 5, 2005 by noggin

[Stoxs]

right heres one for the experts!!!

why does 528 dam air always need to come from the east ?

i accept it does come from the north obvious not south obvious

why not west ?

1, does the atlantic warm the air before it gets here?

2, jet stream involvement

3, it does i just have not witnessed it

[Thundery wintry showers]

Air from the west is usually warmed substantially by the Atlantic Ocean. That said, 528dam air from the west is far from unknown, and indeed until the late 1980s, it was quite common for polar maritime airmasses from the W and NW to be associated with snow showers in northern and western Britain. The setup can still deliver these days, most recently on Christmas Day 2004, although 18 January 2005 also delivered some sub-528dam air via a westerly and some snow for Glasgow and Belfast.

[Stoxs]

ahh ok TWS thanks i was just watching the cold air mas over canada north us and it seems to move north most times

[Daisy]

Hi all,

Please could someone help me to understand the GFS ensembles. I think I am OK with the top set of data but what are the bottom lines on the chart refering to? For example, in the chart below there is a very noticable peak around about day 21 coloured in a turquoise /green colour. This is followed by a slightly smaller peak in blue.

Could anyone explain to me what these signify?

Thanks very much,

regards

D

[chewy2]

Hello all. Have only just found this thread and as I am still very much a learner have found it very interesting.

Daisy - I believe the lines at the bottom of the Ensembles chart show the different ensemble members' predictions for amount of precipitation read against the numbers in mm on the right hand side of the chart. Im sure one of our experts can correct me if i'm wrong.

[Guest Mr_S]

Chewy2, Unless ive been reading the Ens's wrong for months now - you would be spot on

[Nath]

Just like to say that this thread is excellent, I have learned loads!! Thank you all very much

[Daisy]

Thank you Chewy2 and Mr S

I am often up before most of the board are posting so I'm trying to fathom out the GFS 00Z charts and ensembles myself and then check back on what the forum are saying later.

(Have to say my interpretations are generally way off! ) but at least I'm trying!

So thanks for all your help folks- you've been great!

I'm sure I'll have loads more questions......

D

[Stoxs]

right what relation does air thickness have to air temp

would i be right in thinking that thin air is colder ?

what is the equation between the two?

or am i barking up the wrong tree again

[johnholmes]

right what relation does air thickness have to air temp

would i be right in thinking that thin air is colder ?

what is the equation between the two?

or am i barking up the wrong tree again

hi

Ait thickness usually refers to two distinct levels of air. The first one is that between 500mb(about 18,000ft) and the surface(usually, but obviously not always=1000mb).

The second one quite often used is 850mb(about 5,000ft) and the surface.

In each case the lower the numbers you see then the colder that thickness of air is, so a low 500mb 'thickness' means the air depth is lower than a 'high' thickness which means that the depth is thicker.

So what you are saying is correct.

How do they relate to the temperature on the ground?

Well there is usually a fairly close creelation between low 'thickness' values and relatively low surface air temperatures and vice verca.

hope that helps

John

[Stoxs]

yep i think that has helped john many thanks

ummm

yep got it now

thanks again

[Stoxs]

ok if this link works would this be looking good for an atlantic to form ?

http://www.net-weather.co.uk/index.cgi?act...e=gfsh500;sess=

i am refering to the THE 28/12/2005 12z t384 i know this is FI i am referring to the patten not the possibility of it coming off

[whitestuff]

yes can someone also tell me what an atlantic is?

[Stoxs]

sorry chaps missed an important word out i mean`t to say ATLANTIC BLOCK if i am right this is where two high preasures meet north to south i.e from west of southern england right up to greenland this shuts off the flow from the u.s.a as in low pressures or as some would say zonality .If this happens then it opens the north or east doors for cold air to move over the uk if this is wrong please correct me .and post it up here so others can see it

hope this helps novices not to good at explaining things

[Daisy]

Hope someone can help me with this... Teleconnections!!

I have been trying to understand the posts by Steve Murr and Glacier Point etc... and I am finding it all extremely interesting but it is like trying to learn another language! (Even the help Guide-sorry Steve)

I think I have got to grips with positive NAO. Azores high Greenland low etc.... However am I right in asssuming that it is the positive NAO that causes the jet stream (can someone please define "jet stream") to be strong from (the USA or southern Atlantic?) which causes zonality across the UK in the Winter.

If the NAO is negative then the difference between the Azores anticyclone and Greenland low is much less causing weaker jet stream and less zonality and hence less mild wet weather as we don't have the relatively warm,moisture-laden lows from the Atlantic and it opens the door for air to appear over the UK from other areas depending upon where the high pressure is at that time. E.g if high pressure is to the North of Uk then polar air masses may move down and then across the UK?

Neutral NAO??? :huh:

OK now this is where I get completely stumped. The Pacific Jet is this the part of the jet stream that crosses the Pacific Ocean and hits western USA? Is the Pacific Jet the winds that cause the PNA (Pacific North American Pattern) as in Steve Murrs "guide to Teleconnections"? If PNA is neutral, can this have an additive effect on the jet stream, causing a weak atlantic (is this a.k.a. subtropical jet stream??) jet stream to have a kick up the backside?- so perhaps a return to zonality (cyclogenesis?)?? Is this effect augmented further by a Positive PNA? (Negative PNA jet moves to the south of the UK?) Or is this complete nonsense (politely put!) :lol:

(Is there a jet stream from the USA or is this the subtropical jet ?- does this move up the Eastern coast of the USA but originates from the Azores High?) Is the pacific jet , jet stream , subtropical jet etc all the same wind/ moving air mass progressing over different parts of the world but in one continuous loop that can be split (bifurcated?) or moved from its normal path to a more southerly or northerly direction according to its strength and areas high pressure?) aagh!!

What is the AO? (Atlantic Oscillation?) and then of course there is the QBO, the PFJ...........sorry to use abbreviations but I do not know the proper terms.......

.....the ENSO (-Southern Oscillation? -High pressure in the Pacific, low pressure in the Indian Ocean??-something to do with the El Nino-(ocean warming in the coastal regions of Peru and Equador/Pacific??) Maybe we'll leave that one for a while!

Plus do the trade winds have different names?? Are trade winds surface winds whereas jet stream is higher?

I don't ask for much do I :blush:

Sorry to be a nuisance but any assistance (no matter how small) in trying to understand quite complex (IMO :huh: ) topics would be gratefully received.

Cheers all

Daisy Dullard!

[Paul]

Hi Daisy, I'm not really into teleconnections in a big way so am not the best person to answer your question - I'm sure one of the LRF gurus will be around shortly to help you out though

[SMU]

Hope someone can help me with this... Teleconnections!!

I have been trying to understand the posts by Steve Murr and Glacier Point etc... and I am finding it all extremely interesting but it is like trying to learn another language! (Even the help Guide-sorry Steve)

I think I have got to grips with positive NAO. Azores high Greenland low etc.... However am I right in asssuming that it is the positive NAO that causes the jet stream (can someone please define "jet stream") to be strong from (the USA or southern Atlantic?) which causes zonality across the UK in the Winter.

If the NAO is negative then the difference between the Azores anticyclone and Greenland low is much less causing weaker jet stream and less zonality and hence less mild wet weather as we don't have the relatively warm,moisture-laden lows from the Atlantic and it opens the door for air to appear over the UK from other areas depending upon where the high pressure is at that time. E.g if high pressure is to the North of Uk then polar air masses may move down and then across the UK?

Neutral NAO??? :huh:

OK now this is where I get completely stumped. The Pacific Jet is this the part of the jet stream that crosses the Pacific Ocean and hits western USA? Is the Pacific Jet the winds that cause the PNA (Pacific North American Pattern) as in Steve Murrs "guide to Teleconnections"? If PNA is neutral, can this have an additive effect on the jet stream, causing a weak atlantic (is this a.k.a. subtropical jet stream??) jet stream to have a kick up the backside?- so perhaps a return to zonality (cyclogenesis?)?? Is this effect augmented further by a Positive PNA? (Negative PNA jet moves to the south of the UK?) Or is this complete nonsense (politely put!) :lol:

(Is there a jet stream from the USA or is this the subtropical jet ?- does this move up the Eastern coast of the USA but originates from the Azores High?) Is the pacific jet , jet stream , subtropical jet etc all the same wind/ moving air mass progressing over different parts of the world but in one continuous loop that can be split (bifurcated?) or moved from its normal path to a more southerly or northerly direction according to its strength and areas high pressure?) aagh!!

What is the AO? (Atlantic Oscillation?) and then of course there is the QBO, the PFJ...........sorry to use abbreviations but I do not know the proper terms.......

.....the ENSO (-Southern Oscillation? -High pressure in the Pacific, low pressure in the Indian Ocean??-something to do with the El Nino-(ocean warming in the coastal regions of Peru and Equador/Pacific??) Maybe we'll leave that one for a while!

Plus do the trade winds have different names?? Are trade winds surface winds whereas jet stream is higher?

I don't ask for much do I :blush:

Sorry to be a nuisance but any assistance (no matter how small) in trying to understand quite complex (IMO :huh: ) topics would be gratefully received.

Cheers all

Daisy Dullard!

Hi Daisy-

Ive just seen this post Via a PM from Paul- cant do anything today- but I will put something together tomorrow for you-

best regards

Steve

[smich]

Hi Daisy - brilliant post and some great questions. Teleconnections is a very difficult element of the weather to grapple with, particularly as thier effects are so far "upstream". Sea Surface Temps (SST'S) even more so - what happens to those effects our weather some 4-6 weeks later!

Here's what another novice understands so far about jet stream. I think there seem to be 2: The Tropical Jet and the Polar jet. They exist at the very highest altitudes and contain a hell of a lot of energy. Their influence on the weather should not be underestimated. They travel in waves and pulses that seem to vary depending whether they are over sea or land - this is the oscillation I think, but I could VERY easily be wrong! They also split (bifurcate?) and when this happens to the Polar Jet in the N Atlantic it has a profound effect on our weather. As I understand it, we would like to see the Northern arm go way up west of Greenland and the main southern arm to be flat/go straight across the atlantic way to our S.

Here's a great pic I saw in The Eye in the Sky's winter forecast, that shows the effect of the NAO on the jet:

I'm so glad I started this thread - many thanks to the experts that help out those of us with L plates. Looking forward to reading Steve M's post on this..........or am I????!!! :lol:

Smich

Edited January 4, 2006 by smich

[Daisy]

Thanks for your replies folks.

I don't want to put anyone to too much trouble, :lol: Life's busy enough without annoying newbies!

If there are any textbooks anyone could recommend initially- that would be great. (I'm pretty sure my knowledge isn't up to published papers yet!)- I didn't study Geography after the age of 13 so I've got a bit of catching up to do!

Best regards

Daisy

[Cloudburst]

Good news all, light snow for eastern and central areas tomorrow as far west as the Cotswold, could see a nice dusting. Day time temps in the next few days very cold with a biting windchill.