San Diego mergers and acquisitions attorneys know what Wall Street calls the “black car indicator.” It refers to the limousines lined up around investment banks to ferry home analysts who have spent the night at work working on deals.

The black car indicator must be high this month. August is shaping up to be the busiest month for M.& A. in recent memory, according to New York Times columnist Andrew Ross Sorkin.

There have been nearly $200 billion worth of deals worldwide for the year, including a $1.6 billion “deal jump” by Hewlett-Packard for the data storage company 3Par, pitting H.P. against Dell.

Business leaders seem to be feeling bold again even as the economy remains sluggish.

But a chorus of senior deal makers, who ordinarily would be eager cheerleaders for a mergers revival, are saying: Not so fast.

If you ask them, they will suggest that all the recent merger hoopla may be a positive sign, but it is overdone. One expert put it this way: “Has the dam just broken?

No.”

Most experts don’t foresee an explosion of M. & A.

But the deals are not likely to do much to solve unemployment. Some of these deals are being driven by “savings,” an overused euphemism for layoffs.

“If you can’t grow, how do you support your multiple? You do a deal,” says Robert A. Profusek, head of mergers and acquisitions at the law firm Jones Day.

The cheap cost of capital and the enormous amount of cash on corporate balance sheets estimated at $2 trillion to $3 trillion, may foretell more deals.

Paul G. Parker, of Barclays Capital, suggested that cross-border deals, which represented 35 percent of mergers this year, point to a shifting dynamic in the marketplace that might be less dependent on the health of the United States economy.

Still, it will take a broad pickup in the nation’s economic growth before merger mania can really take hold.

• New York Times “Are Mergers Back? Well, Sort Of” August 24, 2010