Weather question

[TangoWhiskey]

My daughter rode with me over to the airport today to get a current low-altitude enroute chart for some IFR practice tomorrow with a friend. She brought along her iQuest and was running through a weather quiz, asking me questions. We got 33 out of 35 right.

One of the caught me off guard.

One of the signs that a low pressure system is approaching is:

A) High cirrus clouds where you are
B) Clear skies where you are (showed a smiley in the poll, should be a "B")
C) Dense fog where you are


I got the correct answer wrong. I thought through the way weather works and made my best guess. Vote on the poll what your choice would be... make a comment as to why you think it's right. I'll post back what they said was the right answer in a little while. I really want to UNDERSTAND why the correct answer is an indicator of an approaching low pressure system.

 

[Dave Krall CFII]

High ice clouds indicate bad weather within 24 hours.
The reason is because that's what the Jepp book has always said they mean.

 

[cherokeeflyboy]

I am currently in the RDU area visiting family. I just looked outside and observe
SEVERE clear. There is a hell of a cold front wtih an area of low pressure attached headed this way expected to arrive late tonight, or early AM. Based on this, I vote B.

 

[Nav8tor]

I said "A) High cirrus clouds where you are". My thinking is that a low means rising air which would result in high clouds. The clouds would be spread out in advance of the low toward the high because that's how the flow would be at altitude. I'm not 100% sure of the answer. It just seems like the best choice of the three.

 

[Kaye]

Well, I saw high cirrus clouds today, and the pressure went from 3002 this morning to 2978 late afternoon. There wasn't fog, but the haze was ugly down below 4000.

Kaye

 

[Shipoke]

I didn't vote cause i'm not sure (not IR pilot),but best indication for me is Call WX station.
Dave G

 

[Chache]

Aww.... You're in a high pressure area, and they don't stick around, too long, sooooooo........

B) is my answer

The haze around here was really ugly today, just prior to civil twilight,
and we're out in the countryside, with offshore winds!!

Could just about see the rwy from Dn-Wnd. Sheesh! Ya'd think this was "LAX" circa 1970somethin ...
What happened to all that clean air, we're s'posed to be paying so much to keep clean?? (Low lead fuels, no incineration, no aerosols, etc.)

 

[Steve]

Depends

http://www.srh.noaa.gov/key/HTML/Jim_Clouds/CloudTypes/high.html

 

[Let'sgoflying!]

Kinda reminds me of, "If it is good weather now, surely bad is soon to follow"!

 

[TangoWhiskey]

I said "A) High cirrus clouds where you are". My thinking is that a low means rising air which would result in high clouds. The clouds would be spread out in advance of the low toward the high because that's how the flow would be at altitude. I'm not 100% sure of the answer. It just seems like the best choice of the three.

Those that voted "A" got the answer that the quiz gave. High Cirrus clouds indicate the approach of a low pressure system.

That makes sense, reading your explanation above. I voted for "B", clear skies where you are, thinking "a low pressure system sucks in everything around it, so it would be pulling in the moisture from my area, leaving me with clear skies... til it gets here, anyway!".

But I can also see how, with the low pulling everything towards the center, all that air and moisture runs out of room to go anywhere, has to go up, and then spills out the top as ice crystals in the jet stream, and thus I see cirrus clouds.

Anyway, it was an interesting question, and I appreciate you all participating!

Off to go do some flying... talk to you later! It's cold and clear here in the Fort Worth area--should make for some nice flying weather, if not a little bumpy with the winds that are expected later.

 

[wsuffa]

Those that voted "A" got the answer that the quiz gave. High Cirrus clouds indicate the approach of a low pressure system.

That makes sense, reading your explanation above. I voted for "B", clear skies where you are, thinking "a low pressure system sucks in everything around it, so it would be pulling in the moisture from my area, leaving me with clear skies... til it gets here, anyway!".

But I can also see how, with the low pulling everything towards the center, all that air and moisture runs out of room to go anywhere, has to go up, and then spills out the top as ice crystals in the jet stream, and thus I see cirrus clouds.

Anyway, it was an interesting question, and I appreciate you all participating!

Off to go do some flying... talk to you later! It's cold and clear here in the Fort Worth area--should make for some nice flying weather, if not a little bumpy with the winds that are expected later.

Troy,

Aside from the technical meterological explaination, if you fly a lot of long-distance flights it becomes intuitive. Fly along the front - or fly from HP into LP, or vice versa, and after enough time, you'll see the cloud picture.

Clear skies are generally characteristic of a large high pressure area - but they give no indication of the coming weather. HP can stay in place for long periods of time, without approaching LP.

Bill

 

[ejensen]

Red sky ....................

 

[rmciottijr]

After studying all this weather for my IFR I believe that the low pressure will cause the air to rise as it rises the air will cool. Cooler air does not hold moisture as well so it will condense into clouds. that is my $.02

 

[silver-eagle]

"High cirrus..." would be my guess. Being VFR ONLY, I do what most weathermen do, if the rock is wet, it must be raining. If warm, sunny. If white, snow.
800-WX-BRIEF usually helps.
But this is New England. That could change in a minute.

 

[cwyckham]

One of the signs that a low pressure system is approaching is:

A) High cirrus clouds where you are
B) Clear skies where you are (showed a smiley in the poll, should be a "B")
C) Dense fog where you are

I wish I knew more about weather.

The question itself doesn't really make sense to me. I was taught that high cirrus, especially the type that moves in from the West and covers a lot of the sky means that a front will come through in the next 12-24 hours. My experience has shown this to be true as well.

However, what is a "low pressure system?" Isn't really bad weather generally associated with fronts? Usually fronts seem to center around a low like spokes on a wheel, and the closer you get to the low, the closer the fronts are. Did they mean a front that is associated with a low? Or are they saying that cirrus means that the low itself is coming?

I just got a copy of Buck's 'Weather Flying,' so hopefully that will shed some light on things for me.

Chris

 

[cwyckham]

I said "A) High cirrus clouds where you are". My thinking is that a low means rising air which would result in high clouds. The clouds would be spread out in advance of the low toward the high because that's how the flow would be at altitude. I'm not 100% sure of the answer. It just seems like the best choice of the three.

At the ground level, wind direction is from high to low as one would expect, but at altitude the winds flow around the low, parallel to the isobars due to the Coriolis (sp?) effect. Since the fronts are more or less perpendicular to wind direction (discounting the change in direction accross them), that's why fronts tend to move around low pressures areas like spokes of a wheel.

I think.

Chris