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.

Despite the fact that the Nasdaq was closed for more than two and a half hours today, stock indexes are moving solidly higher. The Dow Jones Industrial Average (DJINDICES:^DJI) is up 0.37% at 3:10 p.m. EDT, and the S&P 500 (SNPINDEX:^GSPC) is up 0.74%.

There wasn't a lot of economic news today, but weekly jobless did rise 13,000 to 336,000 last week -- one of the lowest levels in five years, though it was higher than economists' expectations. Markit's flash manufacturing PMI reading rose slightly to 53.9, indicating that conditions are improving in manufacturing.

Caterpillar (NYSE:CAT) is one of the big winners today, rising 1.8%. Earlier this week, the company reported a 9% drop in sales for the three-month period ending in July, driven by a 28% drop in Asia-Pacific sales. Sales have been falling since late last year, and the slowdown in Asia is concerning not only for Caterpillar, but also for the global economy. Estimates for Caterpillar's full-year earnings have also dropped rapidly from $6.87 per share 90 days ago to $6.33 today. Strong manufacturing data and a rise in the markets are helping push the stock higher today, but the fundamental trends don't look terribly favorable, which should be a bigger concern for investors. 

The big loser today is Hewlett-Packard (NYSE:HPQ), which has tumbled 12.2% after reporting earnings last night. The company's revenue dropped 8% in the fiscal third quarter, and adjusted earnings dropped 15%. Poor performance in the business enterprise unit was cited as the biggest challenge, and things don't look to be getting better any time soon. CEO Meg Whitman said she doesn't expect the company to grow revenue next fiscal year, eroding speculation that a turnaround is imminent. HP's stock has rocketed higher this year, but remember that the underlying business is still very weak, and investors looking to get in now may be falling into a value trap.  

Fool contributor Travis Hoium has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.