### Author Topic: Formula for estimating cloud base. Explanation please  (Read 828 times)

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#### attherubicon

• Member
• Posts: 3
##### Formula for estimating cloud base. Explanation please
« on: March 28, 2021, 09:38:29 PM »
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4

#### sky_watcher

• Contributor
• Posts: 125
##### Re: Formula for estimating cloud base. Explanation please
« Reply #1 on: March 28, 2021, 09:55:31 PM »
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4
From the Cloud Base Calculator site:

The rate at which air cools is estimated at 5.4°F per 1000 feet of altitude. The dew point decreases slower - at about 1.0°F per 1000 feet. That means that per 1000 feet, the spread decreases by 4.4°F.
“The more a man knows, the more willing he is to learn. The less a man knows, the more positive he is that he knows everything...” ― Robert G. Ingersoll

#### attherubicon

• Member
• Posts: 3
##### Re: Formula for estimating cloud base. Explanation please
« Reply #2 on: March 28, 2021, 09:56:46 PM »
Thank you.

#### CW2274

• Forecaster
• Posts: 6272
##### Re: Formula for estimating cloud base. Explanation please
« Reply #3 on: March 28, 2021, 10:16:25 PM »
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4
The rate at which air cools is estimated at 5.4°F per 1000 feet of altitude.
Just as an FYI, known as "standard lapse rate".