Disable highcharts tooltip on certain lines, leave it enabled on others?

UPDATE

use enableMouseTracking: Boolean

Notice enableMouseTracking: Boolean was introduced after this question was asked

Old Answer

I just Disabled the heights point in the Tokyo series

here is your code

         tooltip: {
                formatter: function() {
                    
                    if(this.series.name == 'Tokyo' && this.y == 26.5 ){
                      return false ;
                    // to disable the tooltip at a point return false 
                    }else {
                        return '<b>'+ this.series.name +'</b><br/>'+
                        this.x +': '+ this.y +'°C';
                }   
                }
            }

jsfiddle