Warning lines are another amplitude measuring tool.
WL's are used at half amplitude intervals, i.e. one fractal wave scale smaller than the fork, parallel to the MLU for WL1 and MLL for W-1.
If on the SPX we look at D012 and add in 1 set of WL, WL1 and WL-1 we see the following.
As with the rest of MAP Wave analysis the nomenclature is the same - Wave scale precedes abbreviations eg. W012WL-1 means Weekly fork 012 warning line -1.