Topic: Wind and Humidity Correlation Questions - Cause and Effect or Exclusive?

[galfert]

I've noticed that when the humidity reaches 100% at night there is no wind activity. There is never any wind with 100% humidity in central Florida that I've noticed. The minute the temperatures begin to rise in the morning with sunrise the winds pick up. At that time the humidity drops too and the temperature no longer matches the dew point. At the end of the daylight hours later when humidity rises and as it reaches 100% the wind stops. That happens every night here. So no wind at night normally. I haven't exhaustively researched this. But I Googled and found no good easy search results.

On one particular night recently I noticed a bit of wind recorded...(not typical for there to be wind inland where I am at night). And I noticed that during the moment of wind the temperature and dew point lines separated from each other too, meaning humidity dropped from 100%.

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There was no pressure change and no rainfall during that period 3AM - 4AM.

- Why is there no wind when humidity is 100%?
- Which is the cause and which is the effect? Wind causes humidity to drop? or Temp rises causing humidity to drop and then Wind happens? Which comes first?
- Is it possible to have wind with 100% humidity? (maybe during a hard storm?)

I realize this may be a can of worms and it is really much more complicated that it looks. But I'm just trying to learn what I can. For example I recently learned that when it rains the humidity isn't 100% necessarily. And I also learned that it is a myth that you can count the seconds between lighting and thunder to estimate the distance of the lightning.

[Old Tele man]

Wind "stirs" the air mixture. With no wind, cooler air settles down to ground, while warmer air remains above, so fog occurs at ground level.

Add some wind, and the upper (warm) air mixes with the lower (cooler) air, inhibiting fog (ie: point where T = Td = Twb).

[galfert]

Oh okay, thank you for that explanation.  That got me to think more clearly on this.

Looks to me that Wind and Temp/Humidity can both be cause and effect depending on circumstances.

Situation where Wind causes Temp rise and humidity to drop:
Nearby night storm moves the surrounding air and stirs things up and then temp rises and humidity drops.
(come to think of it that night I noticed night wind that even though I didn't get rain or pressure change I think nearby did get a bit of rain)

Situation where Temp rise and humidity drop causes Wind:
Sun rises and heats up air. Newly warmed air wants to rise and stirs things up. This causes humidity to drop and also causes wind by rising hot air.

Still don't have an answer for if wind is possible at 100% humidity and for humidity to maintain at 100%.  I think probably yes. There might be mixing of air but it is all the same temperature so humidity doesn't change....maybe?

[Old Tele man]

Oh okay, thank you for that explanation.  That got me to think more clearly on this.

Looks to me that Wind and Temp/Humidity can both be cause and effect depending on circumstances.

Situation where Wind causes Temp rise and humidity to drop:
Nearby night storm moves the surrounding air and stirs things up and then temp rises and humidity drops.
(come to think of it that night I noticed night wind that even though I didn't get rain or pressure change I think nearby did get a bit of rain)

Situation where Temp rise and humidity drop causes Wind:
Sun rises and heats up air. Newly warmed air wants to rise and stirs things up. This causes humidity to drop and also causes wind by rising hot air.

Still don't have an answer for if wind is possible at 100% humidity and for humidity to maintain at 100%.  I think probably yes. There might be mixing of air but it is all the same temperature so humidity doesn't change....maybe?

Yes, it's possible but it depends upon which direction "...the wind blows..." whether UP-slope (yes) or DOWN-slope (no)...ie: look up "rain shadow"

[CW2274]

And I also learned that it is a myth that you can count the seconds between lighting and thunder to estimate the distance of the lightning.

Where in the world did you learn that from??

[CW2274]

BTW, another factor for fog formation beside calm wind is a clear sky, this allows for proper radiational cooling allowing the temp to fall to the dew.

[CW2274]

Somewhat related, and not to be Captain Obvious, but in the winter time here we fall below freezing generally no more than half a dozen times. When the threat is expected, I'll watch the dew point, not the temp. Since it's impossible for the temp to drop below the dew, that gives me a more definitive picture on whether I need to drip the outdoor faucet and turn on my incandescent for the plants.

[galfert]

And I also learned that it is a myth that you can count the seconds between lighting and thunder to estimate the distance of the lightning.

Where in the world did you learn that from??

Where did I learn the myth that I thought to be true for decades or where did I learn that what I had been taught was wrong? Well here is the answer to both. I was wrongfully told by a grade school teacher to count seconds and that equalled miles away where the strike happened. It wasn't until maybe 10 years ago that doing weather reading research online that I learned it was a myth. So that stuck with me for a long time. I know adults today that still think that myth is true. The missing part of the lesson incase anyone doesn't know is that you have to divide the seconds by 5 to get the distance in miles. 10 seconds equals 2 miles.

[galfert]

Somewhat related, and not to be Captain Obvious, but in the winter time here we fall below freezing generally no more than half a dozen times. When the threat is expected, I'll watch the dew point, not the temp. Since it's impossible for the temp to drop below the dew, that gives me a more definitive picture on whether I need to drip the outdoor faucet and turn on my incandescent for the plants.

Please elaborate on this. I understand that the temp can't be below the dew. But why do you watch the dew instead of temp? At what temp do you drip the faucet?  Is it because dew is a relative indicator of overnight low?  I should probably delete this post.... I think I got it. I'm answering my own question.

[Old Tele man]

Typical "speed of sound" at ground level is roughly 1100 feet-per-second (actually 1,082 fps), hence about 5 seconds for sound to travel 1 mile (5,280 ft).

[CW2274]

And I also learned that it is a myth that you can count the seconds between lighting and thunder to estimate the distance of the lightning.

Where in the world did you learn that from??

The missing part of the lesson incase anyone doesn't know is that you have to divide the seconds by 5 to get the distance in miles. 10 seconds equals 2 miles.

Ahhhh, I see, you merely said "count the seconds" is wrong, so I assumed you meant all second counting was wrong. You meant "one second per mile" is wrong. That is obviously is true.

[galfert]

And I also learned that it is a myth that you can count the seconds between lighting and thunder to estimate the distance of the lightning.

Where in the world did you learn that from??

The missing part of the lesson incase anyone doesn't know is that you have to divide the seconds by 5 to get the distance in miles. 10 seconds equals 2 miles.

Ahhhh, I see, you merely said "count the seconds" is wrong, so I assumed you meant all second counting was wrong. You meant "one second per mile" is wrong. That is obviously is true.

Yep I see my mistake. I worded it poorly.

[CW2274]

Somewhat related, and not to be Captain Obvious, but in the winter time here we fall below freezing generally no more than half a dozen times. When the threat is expected, I'll watch the dew point, not the temp. Since it's impossible for the temp to drop below the dew, that gives me a more definitive picture on whether I need to drip the outdoor faucet and turn on my incandescent for the plants.

Please elaborate on this. I understand that the temp can't be below the dew. But why do you watch the dew instead of temp? At what temp do you drip the faucet?  Is it because dew is a relative indicator of overnight low?  I should probably delete this post.... I think I got it. I'm answering my own question.

If the OAT is say 35F and my dew is low 30's, even upper 20's, and looks to me if it'll stay that way, I'll forgo the outside stuff. That being said, if subsidence after a departing storm will rapidly overtake the area and the dew is expected to crash, which is common here, then expect the temp to follow suit.