Reports that Japan's Ministry of Finance is abandoning its custom of telegraphing intervention risks and may instead enter the FX market to surprise market participants, has traders on edge. The idea here is the prospect of surprise intervention may make speculators think twice before adding to bearish JPY positions, says CBA economist Joe Capurso. With U.S. markets closed for Independence Day celebrations, currency liquidity will be thin--an ideal time to have a large effect on the market, he adds. The MoF has surprised markets with interventions during public holidays before. (james.glynn@wsj.com; @JamesGlynnWSJ)