As convenient as it may be to track an impulse wave decline (and perhaps consider a top call) given Friday's decisive sell-off in stocks, we have to reconcile or live with the fact the different benchmark indexes have registered their nominal highs on different days or different hours of the day. Chart 1 highlights the asynchronous nominal highs. (Another challenge is the location of Friday's gap at the open. See discussion below.)
If one works with the assumption that stocks have not only registered working tops here but also topped at the same time, it is likely best to track the sell-off from an orthodox high.
Chart 2 (red count) illustrates the idea with the SP500. Chart 3 and Chart 4 offer the same perspective on the Dow and the NDX, with terminal triangles prior to the proposed orthodox highs.
If so, Friday's low would be the end of an initial five-wave decline (wave i down). A counter-trend (wave ii up) rebound is likely in progress. Further selling should surface following the rebound.
While the asynchronous tops among indexes are probable in theory, they are also the principal challenge to a top call. The other major challenge to a top call is the location of the still-unfilled gap at Friday's open. Odds favor the gap to be filled before long. See our analysis in This Gap is Different (8/23/13) . In this case, new highs are probable since these gaps are only points way.
The blue counts in Chart 2 to Chart 4 track this top bullish scenario, where one more new high comes next.