The answer to that first part of that headline is going to be very useful.
The second part of the headline (the line in the sand at 135) is mere speculation on my part.
Anyway, I posted this yesterday during the Asian session here:
I think the info in there is going to be of use, so ICYMI, click on that link. In summary though - the key sign of imminent intervention is a hardening of the rhetoric out of Japan. What you want to be alert for are headlines like this:
- we do not want to see one-sided moves in FX
- we do not want to see excessive moves in FX
- FX movement is not reflecting fundamentals
- we will not tolerate speculative movement
- The Ministry of Finance will combat excessive moves
Comments like these will come from Japan's Ministry of Finance (&/or the BOJ, but mostly from the MoF). Note the BOJ will conduct the operation, but it'll be at the direction of Japan's Ministry of Finance - thats how they do things in Japan.
This is a monster slide for the yen, the MoF will not allow it to move in a straight line (at least, they'll try to slow it):