sigwx charts Tropopause H/L

[aslan1982]

Hi

I been swotting up on sigwx charts and one thing I dont understand is these symbols that look like

240 240 280 340
H L L

I know there symbols for tropopause High, Low or levels

But what is the difference between a tropopause High and low and why would there be more than one of the same ie two different Tropopause lows with different flight levels.

Why wouldnt there just be a simple tropopause level

Thanks for the herlp