We had a definitive strong down-day with the indices particularly weak in the last hour, rolling over, getting clobbered and closing at the lows for the day going away.

Although the day started out with a gap down, they did rally in the morning, snapping back sharply early on but failing to take out resistance. The S&P 500 got nowhere near the levels of the NDX in terms of testing resistance, and they rolled over, had a mid-morning consolidation that failed to break through intraday resistance again and took another leg down that left them sharply lower at mid-day. At that point the indices had completed a five-wave decline that I felt should result in some sort of snapback, and they indeed got a pretty decent one, but that failed to get through declining tops lines and moving averages, and then late in the day they rolled over and came down hard.

Net on the day the Dow was down 361, the S&P 500 down 44.6, the Nasdaq 100 54.5, and the Philadelphia Semiconductor Index (SOXX) down more than 11.

The technicals were gargantuan to the downside, by 10 to 1 on advance-declines on New York, and 4 1/2 to 1 on Nasdaq. Up/down volume was a little worse than 3 to 2 negative, but total volume was heavy at over 2.6 billion on New York. Nasdaq had about a 7 to 1 negative ratio and traded a little under 2 1/2 billion. So, volume was heavy on the downside today with strong downside technicals.

TheTechTrader.com board, as you can imagine, was vastly negative, with many point-plus losers. Shippers led the way on the downside, down 9.78 on DryShips (DRYS), 7.48 on Excel Maritime (EXM) and 3.65 on TBSI.

VMware (VMW) gave back 8.44, and Aluminum Corp. of China (ACH) lost 4.02. The XLE, one of our short portfolio positions, dropped 2.75.

On the plus side, the short ETF instruments that we've added recently to our portfolio were up nicely today. The SDS jumped 2.66, the QID was up 1.40, and the DUG oil-and-gas ultrashort was up 2.24 today, with the drop in crude oil off its morning highs.

Other stocks on the downside, Ascent Solar (ASTI) shot up to nearly 24 this morinng but closed at 21.68, a big negative downside reversal, down 1.52 on the day. Energy Conversion Devices (ENER) gave back 1.39, EPAY 1.32, GigaMedia (GIGM) 1.37 and Global Solutions (GSOL) 2.46.

Home Inns & Hotels (HMIN) fell 2.17, Immersion Corp. (IMMR) 1.16, and Sigma Designs (SIGM) gave back 2.21 today in a weak tech sector.

There were only several small fractional gainers, but no point-plus gainers other than the short instruments.

Stepping back and reviewing the hourly chart patterns, the key to today's action, particularly late in the day, was the break of key short-term support on the Nasdaq 100 at 2180, closing at 2169.55. The S&P 500 similarly took out key support at 1490, closing at 1475.51, a definitive break in both indices, with apparently more downside to come.

We've been anticipating this for more a week now, and it looks like the downtrend is now underway in full force.

Harry Boxer is a technical consultant to many Wall Street hedge funds and large institutional traders, and author of TheTechTrader.com, a real-time diary of his day, swing and intermediate-term trades. For more of Harry Boxer, sign up for a free 15-day trial to his Real-Time Technical Trading Diary, or sign up for a free 30-day trial to his Top Charts of the Week service.