Low pressure-- what does it mean?

[brianjohn]

Alright, feel free to flame away because I should understand all this, but obviously I don't.
I constantly hear my instructors refer to a "low pressure system" and consequently "expect bad weather."
So what exactly is a low pressure system, and what does it mean in terms of the weather that follows it? Adversely, what is a high pressure system and what weather can you expect from it?
Also in regards to weather, thunderstorms are obviously a no-no when it comes to flying. So, if you're already in the air and assuming you don't have weather radar in the airplane, how does a pilot know if they are about to encounter one? What weather information sources does one use to see if there are going to be any affecting their route of flight?
Thanks for the help!

 

[52vincent]

here it is simply put:

Air rises near low pressure areas. As air rises, it cools and often condenses into clouds and precipitation.Due to the counterclockwise circulation around low pressure areas in the Northern Hemisphere, cold air will likely be found to the north and west of low pressure areas while warm air is most often found to the south and east of low pressure areas

Air tends to sink near high-pressure centers, which inhibits precipitation and cloud formation. This is why high-pressure systems tend to bring bright, sunny days with calm weather.Air flows clockwise around a high-pressure system in the northern hemisphere. As a result, regions to the east of a high-pressure center often have northerly winds bringing in relatively cold air while regions to the west of a high-pressure center have southerly winds bringing in relatively warm air.

Flight service provide a wealth of information regarding your route of flight, not to mention the preflight Iam sure you did.
Contact flight watch 122.0
Hope this helps

 

[tarp]

"thunderstorms are obviously a no-no"

Especially in your case right now (and I'm trying not to be cruel or flame you). But you have to have a better WX understanding than you have right now for a ME Commercial Instrument Pilot.

Find a book dealing with weather that you can understand or start watching the weather channel - something. I'm a bit of a weather nut even before I became a pilot. I loved the science of weather.

Air masses (low/high) and fronts (cold/warm) are the basics of weather. If you are in Arizona under cloudless skies for 361 days a year, this may seem like some strange world but in other parts of the world, the weather changes from low to high and warm to cold. The air masses (low/high) have circulation patterns that will affect the kind of weather produced (as mentioned above). In the east, a low pressure system swirling counter-clockwise sucks moisture off the two bodies of water (Gulf of Mexico and Atlantic) and delivers it to places far away depending on strentgh and season. But again, you need much further reading than this board.

As to T-storms. Life starts with equipped vs. non-equipped flyers. In my non-radar Cherokee, summer flying includes lots of morning flights and healthy distrust of towering cumulous. Watching the weather maps for cold fronts and lifting action. Leaving a way out of trouble in a Cherokee usually means flying close enough to the ground that if forced, I can run for a friendly airport and wait out a storm rather than trying to fly IFR though unknown and potentially dangerous weather.

In equipped and capable aircraft (like a regional Jet) radar and the ability to climb to flight levels avoids a lot of the "little" storms. But I and luckily our dispatchers have a healthy fear of huge lines of t-storms outside the abilities of the jet. If the weather is really bad, we don't even launch. If the weather is marginal or we have "holes" in the t-storms, we use our equipment to blaze a path through. (The path being through a hole in the line of t-storms - nobody but hurricane chasers fly through t-storm cells on purpose!)

 

[brianjohn]

Thanks for the input guys.
Tarp, I know you're not trying to be cruel, and I fully know I need to have a much better understanding of weather at this stage of the game.
I'm not trying to blame anyone, but it seems like my instructors never really took any time to teach weather in any detail. Also, it is extremely hard for me to pick up a weather book and follow it, understand, and especially absorb it. Those books always lose me, and I end up getting frustrated. To me, trying to look at stuff such as prognostic charts is like trying to read Greek. But, since I don't know that much, I also have a very high and healthy respect for that which I don't know. I'm not about to go blasting into actual IFR by myself because I'm not sure exactly what is going on up there.
So in essence, it's not that I decided I didn't want to learn about weather; quite the contrary. I have spent many hours trying to read weather books, only to get very frustrated and put them down.
Thanks.

 

[tarp]

BrianJohn:

Wow, now there's an honest answer. Wish you were nearby so I could take on another student - but.....

Here's what I would suggest - the old standby on Aviation weather is AC-45, the FAA's Aviation Weather Handbook. Now I know you get about two pages in and the thing starts talking about Coriolis Effect and the eyes start glazing over and you skip pages.

And now I go back to my dad and my homework when I was a kid. There was a worn out (and I mean threadbare) dictionary on the corner of a bookshelf in our living room. I would ask a question about "what does this mean" and Dad would point to the dictionary and say, "look it up". Now, thankfully, dad only went one level with that. That is, he would start filling in the blanks where the dictionary left off, but I got pretty good at looking up words in the dictionary.

And I'm afraid that is how you are going to have to discipline yourself to learn this stuff. Read very slowly. Read one page and one sentence at a time. If you reach a word that you don't understand or only think you understand - look it up.

The weather book starts with the SUN and how it beats down on our little planet and heats up the atmosphere. This creates a scientific effect like a pot of boiling water known as convection and advection. And so it begins.........

For me, the relationship between our atmosphere and a pot of boiling water is pure and simple science that I love and understand. For you - you need to work at it - you will have to study a little more science just to get off the first page. But be a "british Bulldog" about it. Just sink your teeth in and keep tearing at each sentence until you understand. Don't try and make sense out of weather maps (skipping way ahead in the book) if you can't tell a maritime low system from a desert high pressure system - it isn't going to work.

The one good thing is that you suddenly have a desire and a reason to learn this subject (motivation). I know what its like trying to learn something that seems intangible to you - but if you just break it down (one page per day) or some other small goal, I swear you can get it and be much stronger for it.

Good luck.

 

[brianjohn]

Tarp- thanks immensely for the time and help. I think you offer a great answer and a simple approach to solve my problem: take it one page at a time.
One problem I have had with myself since the first day I started flying was I get down on myself constantly for not knowing everything there is to know. I am beginning to realize that the learning process IS a lifetime process and should be pursued that way.
Hence, I won't bite off more than I can chew, and only move on to the next step after I have the first thing down.
90% of the time, if I'm curious about something, I get into the books until I find the answer. But the remaining 10% is when I get frustrated from not understanding, which causes me to lose interest pretty quick.
Thanks again!

 

[Singlecoil]

Your profile says you are a college student. I took Atmospheric Sciences 101 long before I ever thought about flying and learned a lot about weather. That might be a good place to start.

 

[cookmg]

I think BrianJohn is a very typical low time pilot. I would say that many (atleast at the private pilot level) pilots do not have a good command of weather material for the reasons that BrianJohn mentioned. I remember my instructors telling me the way they make weather decisions is to look outside and decide whether or not it looks good. I think weather is a part of our education that many examiners and instructors don't spend enough time on. I live and fly in socal now and I know many instructors who can get away with not knowing weather simply because they can avoid the few bad days we get down here. I agree that BrianJohn, myself, and many others should have a higher level of understanding of weather. I began to study myself as I started instrument training. I think BrianJohn is on the right path.

Though I still have aways to go in my studies, here are a few things that have helped me:

Read Weather Flying by Buck. I did per a reccomendation on this board and it really broke it down from a pilot's perspective. The book's not going to teach a complete understanding of weather but it is a start and helped me see what is important to know more about.

After you understand Lows and Highs . . even a little better, start looking at the weather channel charts to see how they are affecting weather. Then you can start guessing what they will do the next day. It's sort of fun . . when you guess right.

Anyways . . like others said: Great attitude. Bad instruction is no excuse for not wanting to learn more. I don't think you should be embarassed at all. Leave that to the CFIs and other pilots who have fooled themselves into thinking they don't need to know anything about weather.

 

[Dot_AK]

BrianJohn:

if you're close enough to a FSS, go visit and ask - those guys love to try to educate pilots on everything.

If you have some spare time, check this out: http://aawu.arh.noaa.gov/
And if you have some of the weather books, dig them out and look up stuff you don't know when going through the site, but it's a great one because you can compare radar, winds aloft, surface map, PIREPs, and sattelite pics just by browsing around.

I know the weather books are typically boring as can be, but don't try to read straight through - skip around a little, open to a random page. Weather books are kinda like reading the bible - anyone who starts from the beginning usually can fall asleep halfway through the first chapter.

Hit up a library or a bookstore and look for any reccomended books, save yourself the time of sifting through all the bad ones yourself.

And of course, keep asking questions. I like listening to people answer and seeeing if I can learn anything new, and I'm sure we'd all rather you learned.