How do I tell cloud base height?

[MJ Poore]

Is it by looking at a skew-t's moisture profile? How do tell? And what makes the base settle at a certain level?

 

[rdale]

CCL -- there's a VERY good training manual at http://www.unca.edu/~dmiller/NWS%20SkewT%20manual.doc

 

[MJ Poore]

Thank you for this. Looks a bit complicated though

 

[cedwards]

Or, you can get a REALLY long measuring tape out.

 

[Angie Norris]

Or...if you know the temperature and dewpoint, find the dewpoint depression and multiply by 200...gives a rough estimation of LCL in feet.

 

[rdale]

Thank you for this. Looks a bit complicated though

It really isn't... Just take your time, you really need to know how to read a Skew-T if you ever want to make your own forecasts, so having it now gives you plenty of opportunity before the next chase season

 

[Melissa Moon]

Well, usually your cloud base will fall somewhere between the LCL and the CCL...you can look on a sounding, determine both (the closer you are to convective temperature the closer the LCL and CCL will be I believe), and just assume that your cloud base is going to be between those two heights.

To determine those on a skew-t, see that link provided above.

 

[Melissa Moon]

Wow Angie...I don't think I ever learned that approximation. Cool!

 

[Nigel Bolton]

Or...if you know the temperature and dewpoint, find the dewpoint depression and multiply by 200...gives a rough estimation of LCL in feet.

Hi Angie,

The multiplication factor is actually 400 feet per degree, so a temp of 30C and a dew point of 15C would give a cloud base roughly 6000 feet. This works very well, as during convection, the atmosphere below the cloud conforms to DALR.

On a teph, it is very likely there is cloud when the sounding is moist, and the profile follows closely the SALR. The cloud base will be found roughly where the air dries out below such a profile segment.

HTH.

N.

 

[Angie Norris]

Melissa, that's a little trick I learned when I was in weather observer class and it works very well.
Nigel, thanks for your conversion factor for degrees C...I'll have to remember it . Mine uses degrees F. The example you gave converted to 86F and 59F gave an estimated LCL of 5400 feet, so that's pretty darn close.
While we're on the subject, does anybody know if there's a specific conversion to meters, or just use the Centigrade version then convert feet to meters?

 

[Dave Gallaher]

That's a great techique to pass along--it's now my first Christmas present.

Thanks, Angie.

 

[MJ Poore]

Thank you all for these techniques and answers.

M

 

[Chris C Sanner]

Or...if you know the temperature and dewpoint, find the dewpoint depression and multiply by 200...gives a rough estimation of LCL in feet.

Wow, very nice technique Angie! That's example number one on why Stormtrack is really special sometimes.

 

[Angel Dimitrov]

cloud heigh

In my area, the CB base is close to LCL, not sure why.

Angel