TOKYO, Oct 12 (Reuters) - Japan's core machinery orders rose 11.0 percent in August from the previous month, government data showed on Wednesday, as rebuilding from the March natural disaster supported corporate capital spending. The rise was much bigger than the median forecast for a 4.9 percent increase in a Reuters poll of 24 economists, and followed an 8.2 percent fall in July. Compared with a year earlier, core orders, a highly volatile data series regarded as an indicator of capital spending in the coming six to nine months, increased 2.1 percent in August. Manufacturers surveyed by the Cabinet Office have forecast that core orders will rise 0.9 percent in July-September from the previous quarter. The government kept its assessment of machinery orders, saying they are in a recovery trend.