Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of TransGlobe Energy (TGA) dropped 13% today after the company reduced guidance.

So what: Management lowered its 2013 production guidance from 21,000 to 4,000 barrels of oil per day to 19,000 to 20,000 barrels per day. The previous guidance figure was given in early May, so this is a quick reversal in the company's expected progress this year. 

Now what: Management said a portion of the planned production was delayed into 2014 and was outside of the company's control. Even so, investors weren't happy, and it doesn't look like production will grow much in 2013. It still expects $145 million in cash flow from operations this year, and that's not terrible for a company with a $450 million market cap, so I wouldn't panic too much today.

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