when the oscillator moves below zero the aroon down is crossing below the aroon up a low occurred more recently than a high which could signal that a downtrend is starting 
limitations of using the aroon oscillatorthe aroon oscillator keeps a trader in a trade when a long term trend develops during an uptrend for example the price tends to keep achieving new highs which keep the oscillator above zero during choppy market conditions the indicator will provide poor trade signals as the price and the oscillator whipsaw back and forth the indicator may provide trade signals too late to be useful the price may have already run a significant course before a trade signal develops the price may be due for a retracement when the trade signal is appearing the number of periods is also arbitrary and there is no validity that a more recent high or low within the last 25 periods will guarantee a new and sustained uptrend or downtrend the indicator is best used in conjunction with price action analysis fundamentals of long term trading and other technical indicators investopedia does not provide tax investment or financial services and advice the information is presented without consideration of the investment objectives risk tolerance or financial circumstances of any specific investor and might not be suitable for all investors investing involves risk including the possible loss of principal 