Driver,

 

1) Yes, you've discovered "geopotential" and the 3D, much easier, view of pressure surfaces :-)  What we see in surface charts is the projection of those surfaces as they intercept sea level surface.

 

But, when you look at contour charts (geopotential height) you're actually reading height instead of pressure, just like in a topographic map. The 500 hPa chart will show heights on it's contours, and not pressures, of course, because it is the 2D representation of the 500hPa pressure level.

 

2) When you cross TA and set your Kollsman accordingly, at 1013,2 ( 29,92 ) ( useful link here for experimenting with QNH settings... ), you are actually telling your altimeter that, from there on you consider that you're traveling across a perfect ISA atmosphere, where the mean sea level pressure is 1013,2 mb.... Well, this not being the case ( most of the time it isn't ) means that as you cross different air masses, the actual 1013,2 mb surface wil actually ondulate, up or down depending on the characteristics of the air mass you're crossing, so, all of your other levels will ondulate as well. So.... setting the altimeter to QNE doesn't mean you will start moving "straight ahead" in a smooth spherical surface, but rather that you consider from there on that you're crossing an ISA atmosphere! No problem, provided all other aircraft around you have their altimeters set accordingly... They're all on a very soft roller coaster :-)

 

Bringing flight simulators to the equation :-), MSFS does not model non-ISA lapse rates for pressure, so, you don't have the "cold airmass" effect simulated, even when using the best weather injection add-ons, although I believe this can change anytime soon for those using ASN. 

 

The same applies to X-Plane ( that one is even more limited in terms of temp and pressure lapse rates...)

 

Aerowinx PSX, THE Boeing 744 simulator, does model geopotential, and even the "Jetstream Constellation" on Earth, depending on date, and other factors... It's actually the first available flight simulator modeling this feature, as you can see on Pages 41 through 44 of this PSX Operations Manual Preview.

I'll keep on reading and hopefully that book i ordered will bring the light bulb on lol

 

As for the altimeter, if you set 1013 and cruising along at FL390 your true alt will be changing depending on the air mass your going over? So your plane isn't always flying in a straight line horizontally?

 

I have ASN so does this mean they'll be modelling this?

Yes to the 1st question, and, I think yes for the 2nd too :-)

My head hurts!

 

The saying goes from high pressure to low pressure watch out below OR from hot to cold watch out below!

 

Now that makes sense but lets say you stick the cold air in the high pressure what happens to that saying now as cold air in the high, compresses the isobars and now you'll be flying from a cold to a low so that saying will change?

 

Do you get what i'm trying to say or am i thinking about it too much lol

Your questions are all excellent, and the same I dealt with because, I'm not a meteorologist, and because I started learning about it all on my PPL syllabus, and when I started trying to figure out all of it in more detail, I came across the exact same problems you have.

 

Regarding your last question, bare in mind that all of these changes occur over long distances, and the height variation of a pressure surface is not that huge, except on extreme cyclonic situations.

 

But theoreticaly you can transit from somewhere in the World in your airliner, from a place where you had a cold high ( like when the Siberian Anticyclone is at it's biggest activity ), to another region with a Low, but just don't think they'll be right next to each other :.-)

 

Think about it more in the line of .... Pressure being more or less the same at surface level, from high T to low T.... 

I think its all coming together and visually picturing that 3D of a high and low and then the fronts it makes sense.

 

I'll keep on reading guys.

 

Has anyone got a good link to see the UK and europe pressure charts?

http://www.wetterzentrale.de/topkarten/fsfaxbra.html

 

 

You get Analysis (based on the Observation ) and Forecasts ( based on the Computational Models ).

 

Look in the top menu where it reads: Europa/Atlantik...

 

But there are many others...

Still on the "cold weather" theme, here's an interesting thread at PPrune:

Still on the "cold weather" theme, here's an interesting thread at PPrune:

I was reading that last night.

 

But its not simulated in ASN :(

 

Slowly understanding these air masses and pressure systems. I'm in scotland and a POLAR MARITIME front just passed over took all morning and day but i actually could understand all the clouds involving the cold front pushing the warm front away and seeing the cold front leave, altostratus clouds and cirrostratus clouds at the tail end. It stretched in one big line from the west to the east. Then came clear skys cold air and high pressure

 

The front is moving south of England.

 

Check this website out guys - http://www.weatherweb.net/wxwebchartsukvissat.php

Isn't it cool to take a look up into the sky and be able to read it that way?

Need some clarify on jetstreaks! I'm reading tom bradbury book and this link http://www.netweather.tv/index.cgi?action=jetstream-tutorial;sess=

 

In tom's book he says air entering the jet DIVERGES (IN) and CONVERGES (OUT)

 

But in the link its reversed, link says it CONVERGES (IN) and DIVERGES (EXIT)

 

Both are conflicting here is a pict of tom bradbury jet stream

 

 

https://www.dropbox.com/s/9xch6i9feewsrgu/Photo%2025-11-2014%2009%2004%2041.jpg?dl=0

Vernon, the rationale is simple:

 

- The Coriolis force is proportional to the wind speed, so, the faster the wind speed, the higher the coiriolis component. 

 

So, Tom's sketch is OK. When the wind accelerates as it passes a through, the Corilois force and pressure gradient reach an equilibrium, and there's divergence.

 

When the wind speed lowers, so does the Coriolis component, and the pressure gradient around a high pressure area is much lower than around a low, so, the Coriolis wins and bends the wind trajectory into the high pressure center, making it converge...

Yes so air at the surface will rise to the area of DIVERGENCE above.

 

In that first link i provided it says,

 

The winds leaving the jet streak are rapidly diverging, creating a lower pressure at the upper level (tropopause) in the atmosphere. The air below rapidly replaces the upper outflowing winds.

 

I thought winds leaving are CONVERGING? Thats what i was geting at why the difference in that link and TOM BRADBURYS explanation?

Ahh jet streak is the trough the curvature? I thought it was at the ends lol

Aerowinx PSX models thi sso damn well....  see pages 41.. of the Manual Preview :-)

 

I love my PSX!!!!