$watch ngModel from inside directive using isolate scope

I am trying to watch my model value from inside my linking function.

scope.$watch(attrs.ngModel, function() {
       console.log("Changed"); 
    });

When I change the model value inside my controller, the $watch function is not triggered.

$scope.myModel = "ACT";

$timeout(function() {
   $scope.myModel = "TOTALS"; 
}, 2000);

Fiddle: http://jsfiddle.net/dkrotts/BtrZH/4/

What am I missing here?