Tesla's stock has surged insanely high in 30 days, and it makes no sense (TSLA)

Getty Images/ Scott Olson

Tesla had a weird end to 2015. The company rolled out its long-awaited Model X SUV in October to much hoopla, but then barely made it own reduced guidance for deliveries on the year, just over 50,000. 

Tesla shared started 2016 by getting clobbered, dropping $100 per share in a swoon from the $240's to the $140's.

The reason was simple: Wall Street decided that for Tesla to grow in accordance with a $30-billion market cap, it needed to execute on building cars.

But Tesla was struggling to do that. 

Effectively, investors were pricing in a by-now familiar Tesla pattern: overpromise and underdeliver (that might sound bad, but it's actually critical outside the financial context for Tesla to overpromise and underdeliver, as I explain here).

But for the past 30 days, shares have been rebounding strongly, up a whopping 44% to $206 in trading on Thursday.

You could be forgiving if you find a swing like this confusing. What could possible has changed investors' moods?

Getty Images/ Scott Olson

Two things. First the obvious, then the confusing. 

1. Tesla started to look cheap, so some of the buying is likely a momentum thing. 

2. Tesla set a date for the reveal of its new Model 3 mass-market vehicle: March 31 in Los Angeles. The car is expected to deliver 200 miles of range per battery charge and cost $35,000.

On number 2, note that I said "reveal." This isn't a launch. It's the equivalent of a Detroit automaker showing us an early version of an all-new model that won't hit the streets for at least a year. Tesla wants to get the Model 3 to market by 2017, but those with good memories will recall that the Model X was delayed for years.

Big car companies reveal new and updated cars all the time, often at auto shows. Tesla is exceptional, with a market valuation at $28 billion that's not too far off Audi's $30 billion, so everything new that it does attracts an immense amount of media scrutiny, far more than what a General Motors or Toyota or even a Ferrari would.

But still, the Model 3 isn't really even a car yet. And yet it's unveiling represents ... over $10 billion worth of market-moving news?

It defies reason.

Getty Images/ Scott Olson

There's a strong possibility that the Model 3 will take Tesla's business to a new level. But we're going to have to wait to find out — at least until late 2017, and even then, Model 3 sales are unlikely to be significant until 2018 or 2019.

In early 2016, all we can responsibly speculate about Tesla is that it will probably sell around 90,000 vehicles during the year, according to the guidance that the company provided when it reported fourth-quarter and full-year 2015 earnings. That's a doubling of production and is commendable, but it's also less than 10,000 cars manufactured per month, when traditional automakers can hit that level without even thinking about it very much.

It's been clear since late 2014 that investors are having profoundly difficult time figuring out where Tesla is going. The booming stock story was replaced with the cruel reality of a challenging car making story. Tesla CEO Elon Musk actually seemed fine with this: he's periodically expressed doubts about whether Tesla should be valued so highly, and his financial focus has always been on positive cash flow, so that Tesla has a stable funding source that doesn't rely on the stock price to do capital raises. 

That always struck me as the mature way to assess the company, limiting one's embrace of whatever vague "disruptions" that Tesla, with its minuscule sales, was bringing to the gigantic global auto market. 

But Wall Street just can't seem to help itself. This most recent Tesla rally looks to be based on one piece of not-terribly Earth-shattering news. Still, the show must go on. But investors have seen this movie already — and should be wary about expecting a different ending.

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