Shy Torque,
It probably doesn't matter to a helo if they are close to the dead stop hover so 30kts sideways at 3000ft is no big deal. Intake Momentum Drag in the Harrier means that either building up a ood deal of sideslip (or even too much reverse speed) can cause all sorts of problems.
Tourist.
So how can you tell when you're in the dead stop hover relative to the airmass around you? IAS stops indicating at 30kts and the vane ain't a lot of use.