Nine months into 2016, and this year is shaping up to be a solid run for stock market investors. Since the calendar flipped to January, the S&P 500 has handed investors total returns of 7.19%, putting the S&P pretty much on track for a double-digit year by the time Dec. 31 rolls around.

That's a pretty stark contrast to the investor sentiment picture out there in the market this fall. As I write, the AAII U.S. Investor Sentiment Bullish Index is below 30%, indicating that individual investors are far less bullish than is typical. While it "feels" like this market hasn't been making much progress in 2016, the performance stats -- and the fact that the S&P 500 is sitting just below all-time record highs -- offers a somewhat different picture.

To take advantage of the "shadow rally" that's been taking place in 2016, we're turning to a fresh set of Rocket Stocks worth buying for October gains.

For the uninitiated, Rocket Stocks are our list of companies with short-term gain catalysts and longer-term growth potential. To find them, I run a weekly quantitative screen that seeks out stocks with a combination of analyst upgrades and positive earnings surprises to identify rising analyst expectations, a bullish signal for stocks in any market. After all, where analysts' expectations are increasing, institutional cash often follows. In the last 369 weeks, our weekly list of five plays has outperformed the S&P 500's record-breaking run by 80.35%.

Without further ado, here's a look at this week's Rocket Stocks.

Walgreens Boots Alliance

It's been an unimpressive year so far for shares of $86 billion international drug store chain Walgreens Boots Alliance  (WBA - Get Report)  . Since January, Walgreens has lost about 5% of its market value from a total returns standpoint, trailing the S&P by a pretty meaningful margin.

But that performance stat masks the fact that WBA has actually been tracking up and to the right since shares bottomed back in the beginning of February. Zoom in to Walgreens' chart, and this stock has pushed up more than 8% off of its lows at the start of the year.

And Walgreens Boots Alliance is within grabbing distance of an important breakout level up at $84 this month.

Fundamentally speaking, Walgreens has been undergoing a big transition following the merger between Walgreens and Alliance Boots at the end of 2014. The combination created a pharmacy behemoth with more than 13,000 stores in 11 countries. The firm's brands include Walgreens, Duane Reade, Boots, and Alliance Healthcare among others. Walgreens also owns a substantial wholesale pharmacy distribution business, with more than 350 distribution centers that reach more than 200,000 healthcare facilities in 19 countries.

Size matters in the drugstore business, where more volume translates into customer stickiness, better pricing with pharmaceutical suppliers and higher profit margins. While regulatory challenges continue to be a long-term pressure for pharmacy margins, the fact that more than a third of Walgreens' sales are generated outside of prescription medications provides some welcome diversification for its income statement.

This week, with rising analyst sentiment in shares of Walgreens Boots Alliance, we're betting on this Rocket Stock.

Walgreens Boots Alliance is a holding in Jim Cramer's Action Alerts PLUS charitable portfolio. Cramer and Research Director Jack Mohr wrote on Friday that "we continue to like WBA shares long term as we wait for a decision on the Rite Aid  (RAD - Get Report) deal, regardless of the direction of the decision, to remove the overhang plaguing the stock."

Northrop Grumman

$39 billion defense contractor Northrop Grumman  (NOC)  is the only company on our Rocket Stocks list this week that also happens to actually make rockets. Northrop is one of the biggest defense firms in the world, providing Uncle Sam and allies with everything from aircraft and space systems to radar equipment to IT services. Northrop's expertise in a wide number of similar businesses provides some big overlap opportunities.

Long-term, the defense sector has been under pressure from government budgets. Uncertainty surrounding changes in spending policies has been a black cloud over defense firms' stock prices, and Northrop has been changing to react to the new environment. Like peers, the firm has been doubling down on its technology services practice, which now accounts for about a fifth of sales. Spinning of capital-intense businesses such as shipbuilding a few years back makes Northrop nimbler than ever before.

To that end, management has been pushing a reorganization plan, which will likely end with additional lower-margin units being sold off. CEO Wes Bush is prioritizing profitability over top-line numbers, a focus shift that should become increasingly important if government spending tracks lower and Northrop's expenses have fewer places to get spread across. Despite the politicking that's happening on the national stage right now, the need for high-tech defense capabilities remains elevated, and that means that Northrop's mission-critical products (particularly UAVs, manned aircraft and cybersecurity services) should continue to win contract dollars and help to offset future revenue drop-offs from divestitures.

Micron Technology

Micron Technology  (MU - Get Report)  is enjoying an impressive run in 2016. Year-to-date, this computer memory maker is up more than 26%, rebounding in a big way from a selloff in 2015. Micron is one of the leaders in DRAM for computers, as well as NAND flash storage for PCs and mobile devices. While the slowdown in PC sales has been a major drag on Micron's performance lately, the subsequent higher sales forecasts for the year ahead from PC component makers like Intel  (INTC - Get Report)  have been fueling the recent upside in Micron and its peers.

The market for Micron's products continues to grow. Historically, PCs have used slower hard drives versus the solid-state drives that Micron produces. But a shift toward higher performance from desktop and laptop computers has made SSD storage far more conventional in 2016, and super-fast upgrade cycles in mobile devices have likewise boosted demand for Micron's storage. Micron has been innovating in the memory space recently, partnering with Intel to develop new NAND storage technologies with should lengthen the firm's product lifespan at the same time competing components start to become commoditized.

While sustained profitability has been a challenge for Micron in recent quarters, a meaningful part of the firm's recent financial performance has been shared with other memory stocks too. In other words, it has more to do with the recent soft sales environment for PCs than with Micron specifically. As demand for Micron's memory and storage products comes back, so too should its financial performance.

Meanwhile, analyst sentiment is swinging higher in Micron this week -- and so, we're betting on shares.

Quest Diagnostics

Quest Diagnostics  (DGX - Get Report)  has been a notable outperformer in 2016. Since the calendar flipped to January, Quest has seen its share price rally more than 19%, leaving the rest of the S&P 500 in its dust. And this fall, with shares sitting just below all-time highs, that bullish price trajectory isn't showing any signs of reversing course.

Quest is one of the biggest medical testing providers in the country, with more than 2,000 locations spread from coast to coast. Put simply, if your doctor has sent you for a blood test or you've been through a pre-employment drug screening in the last few years, there's a pretty good chance it was at one of Quest's facilities. Quest provides a lots of those simple, low-margin tests every day -- but the firm has also been working on boosting profit margins by introducing more complex products such as genetic and pathological tests that are often proprietary and less commoditized.

One way Quest combats the no-moat status of its more standard tests is by making it easier for physicians to receive and analyze results, increasing the odds that doctors refer patients to a Quest facility. Quest does that with its web-based physician portal, Care360. Long-term, Quest's biggest tailwind is demographics. As the average population age in the U.S. gets older, demand for medical testing should continue ticking up and to the right, providing a rising tide that lifts all ships in the industry.

Norwegian Cruise Line Holdings

Despite a rough year for cruise ship operators, cruise stocks are starting to see a rebound in analyst sentiment this fall. That's fueling Rocket Stock status for shares of Norwegian Cruise Line Holdings  (NCLH - Get Report) , a stock that's finally showing signs of a reversal in 2016 after backsliding 34% since the start of the year.

Norwegian is the third-largest cruise operator in the world based on capacity. The firm currently has more than 40,000 berths spread across a fleet of 24 ships. The company operates cruises under the Norwegian, Oceania, and Regent Seven Seas banners, sailing to more than 510 vacation destinations around the world last year. Bigger isn't necessarily better in the cruise industry -- for instance, on a relative basis, Norwegian currently has more new ship capacity on order than its bigger peers, which means that the fleet is transitioning younger more quickly.

While tumbling oil prices have been a clear positive for Norwegian, the softer consumer confidence that's come with them hasn't been. Lower operating margins doesn't mean much when companies aren't filling cruises. That said, over the longer-term, Norwegian looks well positioned for growth. Like with Quest Diagnostics a moment ago, Norwegian is a big demographics story. The firm's core customer base of baby boomers is retiring at a record pace, and they're forecast to spend more on leisure activities like cruising in the quarters ahead.

Norwegian's stock price is testing a breakout from its downtrend this fall. A move through $40 looks like another signal that buyers are back in control.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.