AUD/USD has risen for four weeks straight

The AUD/USD chart tells the story. After hitting a six-month low in early December, it's been on a tear. It's gained nearly every day in a rally to 0.7860 from 0.7500.

What's especially strange is that AUD-longs have essentially packed it in during the latest run with the net going from +40K to -13K.

That move certainly looks like some kind of calendar effect.

But that also means it could be reversed in the days ahead, lending some support to AUD/USD as it looks to challenge the October high of 0.7897.

At the moment, rallies in commodities -- especially copper -- are helping to underpin the aussie. Looking forward, it will need some backing from economic data. If the RBA shifts to something more hawkish, the latest rally could be just the start.