Blackrock’s Bob Doll says the turmoil in the Middle East and tragic tsunami and earthquake in Japan will likely hamper markets in the short term, but he continues to think the broader longer-term trend for stocks is upward.

“In the short term, the earthquake and resulting turmoil add to global market risks and will almost certainly depress the Japanese economy,” Doll writes in his latest commentary on Blackrock’s web site. “[And] the turmoil in the Middle East is unlikely to be resolved quickly or easily, meaning that oil market volatility is likely to remain high. Economic fundamentals, however, remain sound. Investors have ample cash to put to work and are still underweight equities.”

“Our base forecast remains that the markets should continue to move in an upward direction over the long term, but we may need to see some additional clarity on the geopolitical front before that can occur,” Doll adds.

Doll says that the oil price spike “at a minimum reduces some of the upside potential for global economic growth and adds to potential volatility in the financial markets”. But he says that Blackrock’s analyses are finding that it would take another $20 to $30 in per-barrel price gains to derail the U.S. economic recovery — something he thinks is unlikely. He thinks 3% real gross domestic product growth for the U.S. in 2011 is a good target, citing favorable monetary policy and a recovering consumer.