I'm pulling my hair out lol you have a warm front and a cold front what pressure systems would you find in these?

 

I seen a diagram with cold air and the isobars were 998 and the warm front was something like 1006? I though warm air reduces pressure as its rising?

The thing is you don't need to get this deep into it to pass a test. You're not studying to be a meteorologist. You should know that lows in the northern hemisphere are anti clockwise. Winds go from high to low. Pressure at 18k feet is about half of sea level, etc. The whys are all extra credit and a credit to you for pursuing the knowledge. It did not click for me right away and I'm still learning more about this all the time. That's the saying after all about getting certified to keep learning...

 

It is to your benefit to understand enough to form a mental picture of how the weather will behave in your flight path. The more you understand all the phenomena, the better you will be positioned to predict winds, precipitation, visibility and other factors.

 

I like to look at the weather data from time to time and then make assumptions about what is going to happen such as how strong the winds will be and their direction, what shapes the clouds will have and how high they will be. The next day I will check again and see how close I came.

Lastly like I said before. Lows and highs form for a variety of reasons. Heating and cooling can both create low and high pressure, but that is all I really understand at this time, the reading gets over my head on that subject area.

Just found this site which may help you understand that these pressure system develop multiple ways.

 

Www.theweatherprediction.com\basic\pressuretypes

Oracle is right.

 

Anyway, when you give the example of a frontal system, you're considering one of the 7 classes of depressions that can be studied, and within these, there are variants...

 

Frontal depressions are indeed an example where one of the air masses has all of the ingredients to generate the pressure differential - it's hotter, usually moist and is also mechanically forced by the colder air. These type of low pressure system occurs mainly at middle latitudes along the polar frontal region, and have a predominant West - East circulation.

 

They can be as small ( at surface level ) as a few hundred miles to more than 2000 miles!

 

At another post I mentioned an example of cold, cutoff Low. This kind of depression is, after the frontal type, the second most common type of Low. They are also called Instability Depressions. They are generated in altitude between around the 500 hPa and 300 hPa, and at all levels the isotherms show a decrease from the borders to the center of the Low. They are also associated with stratospheric intrusion of cold dry air, and high instability.

 

And then there are the thermal Lows, where contrarily to the cold Lows, have the temperature rising from the periphery towards the center. They originate in Summer when the higher radiation levels heat the surfaces of the Continents, which in turn make the air masses above them get hotter, less dense  and thus with a lower pressure...

 

After all part of waht is described on the excellent link above by Oracle

I think its all coming together now. Think i'm just trying to take in every single detail thats my aim oracle trying to judge what the weather is going to be like.

 

I signed up to metoffice aviation weather make use of that

 

Brilliant link oracle

I have a question about altimetry and cold weather.

 

If you are flying along from hot to cold the saying goes...watch out below!

 

Your altimeter will over read and your true alt will be lower so thats a danger now why does your altimeter or plane get low if you fly at the same altitude? Or does the plane follow the isobars that are leading down towards the ground. Because of the cold air compacting them.

Yes, the altimeter is calibrated to a given pressure level, so, the airplane ( pilot flying, or AP ) will follow it, and since it is deeping towards the surface, the height of the aircraft will be bellow the altimeter reading.

What pressure level though? As you set it at 1013 at the TA. 1013 isn't going to be at any FL?

When you set it at QNE, then, since all of the pressure levels above the MSL will actually be bellow it's height should you really be in an ISA atmosphere, you will follow the one that corresponds to the altitude that your altimeter reads, and will be bellow what you would be should be flying on an ISA column of air, instead of  across one which is colder and compressed.

 

But the same will apply when you reach TL and the ATC gives you the QNH. As you descend you will actually be at a lower height than if you were flying on ISA conditions. So, even if the QNH is 1013, and thus there is no jump UP / DN in the altimeter reading as you change from STD to 1013, you will still be lower than what your altimeter reads.

You said it yourself. The pressure level follows those curved lines. The altimeter will read the same altitude even though the aircraft lazily flees along those lines. You won't notice the change in true altitude because it is so gradual.

 

Over a long distance it can mean trouble especially if you forget to change the setting on the altimeter for local conditions.

 

In summer vs winter you will discover the same altitude of say 1000 ft on the altimeter looks very different. In winter the ground will be closer.

were talking about cold air here? so whatever your altimeter is reading, let it be, FL350 360 370 its following a pressure level and that pressure level will be sloping down if its cold? but at that height its constantly cold so it'll be dipping all the time?

Looking at those diagrams on that link I provided it looks like that is generally the case at the higher altitudes. Down as you go into the cold core and and up again as you leave it. The altimeter reading stays fixed the entire time unless you decide to change the cruising altitude.

were talking about cold air here? so whatever your altimeter is reading, let it be, FL350 360 370 its following a pressure level and that pressure level will be sloping down if its cold? but at that height its constantly cold so it'll be dipping all the time?

 

No, actually on cold Lows, it's common to have, above the Tropopause, the curvature inverted. Since most airliners can cruise above the Tropopause, the situation can inded be reverted, but only there.

 

It is related to the very dry stratospheric air masses above those cold Lows.

Sorry i'm jumping about the place, Check out that link in diagram for warm core law TYPE 1

 

Why does the isobars sink in warm air? Doesn't it sink due to the cold?

 

 

Also check out cold core HIGH, the isobars are going up meaning warm air? But its cold lol confused.com

I just got this

 

http://www.amazon.co.uk/Meteorology-Flight-Pilots-Guide-Weather/dp/0713668318/

Driver,

 

Very simple: In a Low, and in 3D, the isobars ALWAYS sink towards the core of the depression, and in a HIGH they always have a "positive slope", irrespective of temperature and air density!

 

BTW: Tom's book is excellent! There are also a few interesting technical docs from the UK MetOffice.

 

I have this book ( unfortunately a Spenish version :-/ ) , dedicated to Soaring and Free-Flight Meteorology. He was also, apart from an excellent meteorlogist at the UK MetOffice,  an excellent glider pilot. If you have the chance, that book would be a great acquisition,IMO.

I found this

 

It's simplest to think of a pressure chart as similar to a geographical map, with highs like mountains and lows like valleys

 

 

Yeh can't wait to read his book!

Back to altimetry i have a cruising alt of FL390 TA is 6000ft in the uk i'm in the 737 ngx once i set QNE 1013 i'm no longer following any isobar pressure is that correct? Will the cold or warm air have any affect on this?

Think i know where i'm getting confused about low/high pressure and cold/warm temp.

 

I was thinking cold air slopes the isobars down but infact its low pressure that does it is that correct?

 

And i was thinking warm air slopes the isobars upwards but its high pressure that does it.