H pressure brings good or poor visibility?

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PPL747

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747
Hi
I'm a student pilot with a checkride coming up very soon, there is one topic in re to weather theory that keeps getting me confused and more importantly I'm getting conflicting pieces of info.
In general I understand that L pressure system would usually cause less stable air, which many times are associated with cumulus clouds and therefore improved visibility, as well my understanding was that H pressure is usually associated with stable air which would more likely cause stratusform clouds with low/ poor visibility. But I just listened to a weather theory lesson from Jason Schappert where he mentioned that with H pressure we get those days with good weather and decent visibility. Obviously I'm missing something. My understanding was that the good visibility are usually related to L pressure. Please if someone can explain it accurately.

Thank you
 
Here’s got to be something in the air that makes the visibility poor, regardless of stability. You get a nice, big high where there’s no moisture around, and there’s not enough instability to pull dust off the ground, you end up with good vis.
 
just remember it's "good" to be "high". so higher pressure = gooder weather.
 
This I understand, if the definition of good weather is stable air mass, but the good or poor visibility part keeps on confusing me
 
As I understand it, with high pressure, there’s less overall moisture in the air, so generally speaking, visibility will be good. With low pressure, moist air will be abundant, allowing for all clouds, rain and lower visibility conditions to be probable.
 
In answer to the to the title of the post, YES.

Usually where I live (NE) high pressure comes from the NW (normally winter but also in summer) or the SW (normally summer, think Bermuda high). If from the SW the airmass will be very humid often with poor visibility sometimes as low as 3 - 5 miles and perhaps air mass thunderstorms. If from NW normally clears out the gunk left over from an unpleasant low and brings clear and unlimited to the area after thunderstorms announcing the cold front passage that precedes the high.

The most important word used above is "normally." Abnormal happens.
 
Unless you have a big moisture generator to the west of you...
 
PPL747 said:
This I understand, if the definition of good weather is stable air mass, but the good or poor visibility part keeps on confusing me
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Explain what a “stable” vs “unstable” airmass actually means.
 
PPL747 said:
This I understand, if the definition of good weather is stable air mass, but the good or poor visibility part keeps on confusing me
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The definition of good weather does not really relate to stability, it's more complex than that. Stable air can cause quite unfavorable weather for flying.
 
And when you are smack in the middle of a high in the upper midwest during the summer and there's no winds aloft, I find the haze layers tops out at about 8000ft or so. Below that the visibility can get iffy.
 
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It is great that you are thinking about Wx. I look at this chart several times a week just see if I can figure out why the weather is what it is. It is a first, pass, almost a guess.

For example why is Erie PA overcast? Same thing with CLE, why broken? But TOL is clear. Not only are there general considerations (all three cities are in the high) but local ones as well. Erie is at the S. end of a trough and on the lake with winds from the N (in the winter it's probably getting pounded with lake effect snow). I haven't checked but I'd guess the overcast will improve as morning lake effect fog burns off.

I'm not a meteorologist and I don't begin to understand why most of what is happening is happening (outside my own corner of the world) so why is WY in a low and skies are clear and vis >5. Why does LAS have clouds? I can make an educated guess but I'm not educated enough to educate others.
 
Get a nice temperature inversion (stable air right?) that traps fog, dust, smoke, etc. at low level, and you will have stable air with poor visibility.
 
Here’s how I think about it, right or wrong-

Stable air is stagnant and stagnant lets particles hang around (smog, fog, low stratus). This weather can be drizzly or a steady rain.

Unstable air is moving. Builds high cumulous. Doesn’t give smoke or fog any chance to accumulate in any one spot.

Don’t equate low or high baro pressure to stability. I think it’s the change and rate of change (gradient) that matters. And the temperature of the incoming moving air mass.

Yes, I’m often confused about weather myself.
 
There is a problem in trying to over-generalize weather, something both OP and Mr. Schappert are doing. For example, thunderstorms embedded in a layer of stratus clouds are not an uncommon phenomena, but an overly simplified idea of weather theory would suggest that such a thing should be impossible.
 
It's perhaps too simple to generalize weather based on barometric pressure alone. In general, low pressure denotes rising air, which, in the presence of moisture, is conducive to clouds and precipitation. High pressure denotes descending air, which usually suppresses large-scale convection and cloud formation. But it is possible and quite common in high pressure areas to have fairly stagnant air which, in the presence of moisture, can produce haze and limited visibility. This is especially common on the backside of a high pressure center, where light southerly flow may draw hot, moist air northward. Think the eastern US in the summer with a big Bermuda high plonked just off the coast: lazy, hazy, days of summer. You may get fair-weather cumulus and a high haze layer with poor visibilities. Above the haze layer, it will be clear and a million.
 
Visibility can be bad in high or low pressure areas. Or anywhere in between. Don't get caught up in trying to generalize, it has no benefit.

The only relevant question is "what is the visibility for today's flight?".
 
Since the question is about a check ride and not weather theory on general, here's what the FAA says:

High-pressure systems are generally areas of dry, descending air. Good weather is typically associated with high-pressure systems for this reason. Conversely, air flows into a low-
pressure area to replace rising air. This air usually brings increasing cloudiness and precipitation. Thus, bad weather is commonly associated with areas of low pressure.
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Reality is that it depends, and it's good for you to really understand how weather works, but you should know the FAA answer is high=good and low=bad.

Read chapter 14 of PHAK.
 
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25 yrs of flying the Gulf of Mexico out to 200 nm or so, I and my associates have observed the following: When a summer high is sitting on you, many times vis goes to around 8 miles, at times down to 5, ceilings (if any) about 4 to 6K. When a summer low moves in, vis improves to plus 10. I've seen 12-15 mi vis & blue sky while in the eye of a hurricane. Every day is different.
 
dmspilot said:
The definition of good weather does not really relate to stability, it's more complex than that. Stable air can cause quite unfavorable weather for flying.
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Absolutely! Stability and "good" weather have very little to do with one another. IMC and IFR flying is typically "stable" air.
 
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