Fax chart symbol - new to me

[galba]

I don't remember seeing the zig-zag lines shown on the following fax chart before, - (down the Irish Sea and English Channel), can someone explain them please ?

[Thundersquall]

It's a convergence line:

http://www.metoffice.gov.uk/weather/uk/gui...y.html#pressure

Often seen when we have a northerly and always queried :lol:

And they always seem to have a habit of disappearing around T+24 or less.

[galba]

Thanks Robbie, - Ill try not to query it again ! :lol:

[Supercell]

Just an aside - The FAX charts did not pick up on the convergence line stretching eastwards from Merseyside, last night. I reckon it is one thrown in for the T48 hrs plus.