Storm clouds on the horizon. With even the new Prius off to a slow start, Toyota is rolling out Detroit-style rebates, subsidized leases and other incentives.

It used to be a point of pride for Japanese makers, Toyota in particular.  In fact, senior Asian executives could barely contain their glee at watching their Big Three Detroit rivals run up billions of dollars in costs on the rebates and other incentives needed to keep the metal moving.  Japan, Inc., on the other hand, happily collected a premium over sticker, especially on its most popular models, like the Toyota Prius hybrid.

Or so went the story line.  The reality was never quite so neat.  The Japanese have long had incentives, especially the smaller, weaker makes.  But the big brands generally kept that news quiet.  As Toyota’s Senior Vice President Don Esmond would acknowledge, “We have to remain competitive,” even if that meant just offering some cash that dealers could kick in to clinch a deal.

No longer.  The current economic downturn has been surprisingly democratic.  With sales currently running at just little more than half the peak levels of early in the decade, there isn’t a brand that hasn’t felt the pinch. Even Subaru and Hyundai, which initially seemed to defy the downturn, were off last month.

And then there’s Toyota.  After defying gravity, seemingly for decades, it has suddenly come crashing back down.  Its sales tumbled 41.1% in April.  While it’s clear that the traditional spring buying season hasn’t shaken off the hoary frost of winter, Toyota’s numbers were down much more than the overall industry’s 34.4% drop for the month.  In fact, Toyota saw a steeper dip than almost anyone other than Mitsubishi, down 55%, and bankrupt Chrysler, off 48%.

Toyota’s downturn could be seen across the board, with big drops by perennial Top 10 favorites like the Camry and Corolla, as well as the poster child for the environmental movement, the Prius. 

Indeed, the hybrid’s numbers, so far this year, have been running barely a third of where they were during the mid-2008 fuel price run-up, despite the launch of an all-new version of the Prius.

Intent on heading off the steady slide, Toyota has been taking a variety of steps, including unprecedented production cuts, notably at its U.S. operations.  Now, it’s beefing up the rebates and incentives it used to sneer at – and it’s no longer hiding that fact.

The importer is spending heavily to promote its latest sell-a-thon, which will include cash givebacks, reduced interest rates and subsidized leases.  Leases could prove a strong draw for Toyota, right now.  Leasing, in general, grew sharply over the last decade, largely due to hefty subsidies.  That’s led many makers to trim back and, in the case of General Motors and Chrysler, to virtually eliminate this popular form of car buying.

The incentives will be applied on a regional basis, and in some cases, leases could carry 0% interest rates.

Rebates are also regional, and precise figures can be difficult to get from the automaker, but the Camry carries a cash-back offer of $2000 in some parts of the country, for example.

Not all is bad for Toyota.  If anything, it’s actually stepping up production of some models, including the RAV4 crossover.  And considering the disarray at two of its key domestic rivals, there may be reason for optimism, says  Toyota division general Manager Bob Carter.  “We’re confident we will grow market share through 2009,” he contends.

Of course, in a down market, Toyota would only have to shift its momentum slightly to get on the plus side when it comes to share.  Boosting back sales, even to last year’s already anemic levels, is far more problematic.