The indices have made only minor moves lately, but there's been a mix of action under the surface. Biotechnology, some technology names, China-related plays and the high-momentum FAANG names have been on the plus side. On the other hand, retail, oil and a variety of small-caps have been weak.

The inconsistency is clear when you compare the Nasdaq 100 ETF (QQQ) - Get Invesco QQQ Trust Report , which is up 0.54% over the last eight days, with the Russell 2000 Index Fund ETF (IWM) - Get iShares Russell 2000 ETF Report , which is down 1.53% during the same period.

The market always has winning and losing sectors, but does that indicate that problems are developing? The bearish theory is that this sort of inconsistent action does eventually lead to downside.

Back in 1995, Jim Miekka developed a tool to measure when the inconsistency in the market reached a critical point. He called it the "Hindenburg Omen." I won't go into the exact calculations (read Quantifiable Edges.comfor details) but the Hindenburg Omen tries to identify when there is a strong split in the market action.

The Omen is triggered when there is a high number of new 12-month highs and new 12-month lows, but the ratio of highs to lows isn't greater than 2 to 1. In addition, the McClellan Oscillator must be negative on the same day, which indicates weak breadth.

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Well, the Omen has been triggered four times in the past week, as we had a number of pockets of both strength and weakness at the same time that breadth has been poor.

The statistics developed by Quantifiable Edges show a correlation between a cluster of Hindenburg Omens and a subsequent drop in the market, although it doesn't tend to be the disaster that the name would indicate. This is a rather arcane technical indicator, but I bring it up because it highlights the market's primary theme right now, which is the price action's split personality.

The bulls are unconcerned about it, as there's still plenty of positive action. But the market's overall personality is making many people (including me) uncomfortable. This indicator isn't sufficient for me to don a bear suit, but it does confirm my struggles to add new long inventory. I discussed being bearish by default earlier this week, as I've seen my cash levels grow as I fail to put money to work.

The Hindenburg Omen is a catchy name that tends to generate quite a few jokes, but it does measure an interesting aspect of the market -- a split personality, and that does create some instability. Whether it resolves itself to the downside is the question. We'll just have to stay focused on the price action to see if the Omen is indeed predictive this time around.

(This column originally appeared at 7:35 a.m. ET on Real Money, our premium site for active traders. Click here to get great columns like this from Jim Cramer and other writers even earlier in the trading day.)

At the time of publication, Rev Shark had no positions in the stocks mentioned.