Stock investors may want to fasten their seatbelts for the week ahead, when a flurry of earnings and economic data will once again be in focus.

Concerns over the Iraq elections and the outcome of the next meeting of the Organization of Petroleum Exporting Countries (search), or OPEC, both scheduled for next Sunday, Jan. 30, also could affect investor sentiment during the week.

On the earnings front, there's little evidence to build a case for optimism.

Of the first 117 companies in the Standard & Poor's 500 (search) to report earnings, more have missed expectations on earnings and revenue than at the same time last year, according to Reuters Estimates.

And in the stock market, investors voted their dismay by being quick to sell after getting the earnings news.

For the year to date, the blue-chip Dow Jones industrial average (search) is down 3.62 percent, the broader S&P 500 is off 3.63 percent, and the tech-heavy Nasdaq is down 6.49 percent.

"I think next week is going to be very volatile," said David Scott, portfolio manager at the Chase Growth Fund , which has assets of more than $200 million, mostly in large-cap companies.

"Some companies will come through with nice earnings and guide positively -- others will not. It's a tough week to read."

The earnings season gets into top gear with dozens of the biggest U.S. companies scheduled to report.

Those will include Johnson & Johnson (JNJ), Merck & Co Inc. (MRK) and Merrill Lynch & Co. Inc. (MER) on Tuesday, Starbucks Corp (SBUX) on Wednesday, Microsoft Corp (MSFT) and Caterpillar Inc. (CAT)on Thursday, and McDonald's Corp. on Friday.

On the week's calendar of economic data, the consumer confidence index for January from the Conference Board on Tuesday, durable goods data for December on Thursday, and fourth-quarter gross domestic product numbers on Friday will be closely watched.

Anthony Chan, managing director and senior economist at JPMorgan Fleming Asset Management, believes that corporate earnings will end the season slightly improved.

Chan cautioned, however, that "the climate in Iraq and the climate with OPEC (search) will determine how we view those earnings -- those factors will influence the equity market's sentiment."

Any escalation in violence leading up to the scheduled Iraq elections on Jan. 30 could have an impact on U.S. financial markets, analysts said.

"In the shorter term, you are going to have volatility in the energy markets and the currency markets due to the Iraqi elections -- you can see that concern building up," said Frank Holmes, chief investment officer at U.S. Global Investors, Inc., which manages about $1.7 billion of assets.

OPEC, the oil producers' cartel that controls about 40 percent of global exports, meets on Jan. 30 to discuss whether it needs to cut supplies further ahead of the second quarter, when winter demand slows.

Investors worry about the possibility of higher energy prices because they can squeeze corporate profits and curb the consumer spending that drives the U.S. economy.

Also on investors' minds is the next meeting of the Federal Reserve's (search) policy-setting body, the Federal Open Market Committee (search), on Feb. 1-2.

The FOMC has raised short-term U.S. interest rates five times in succession since last June. But its trend-setting federal funds rate still is considered to be relatively low at only 2.25 percent.

Analysts expect rates to keep rising, but at a "measured" pace that is generally considered to be in increments of a quarter percentage point, or 25 basis points, at a time, instead of larger moves.