Would you ignore a TCAS RA if you couldn't see the intruder? (who might be above you, below you or behind you. Or in IMC).
Can you see a microburst ? Can you see wind-shear?
The doppler RADAR can detect fast moving wet air, i.e. wind-shear or a microburst, so the PWS issues a warning or an action. Why would you ignore that?
What have you got to lose by following a PWS - even if it turns out later to have been false? (as said above, if there is a CB in your go-around path, you should have already told ATC that you will be delaying your approach, or at the very least, turning to avoid it.
Better to follow PWS than assume it is a false warning.
From Airbus FCTM:
WINDSHEAR PHENOMENON
Windshear is a sudden change in either wind speed or direction, or both, over a relatively short distance. Windshear occurs either horizontally or vertically at all altitudes.
Windshear can result from a
microburst.
Microbursts occur close to the ground and are a possible hazard to the safe flight of the aircraft for the following two reasons:
- The downburst of a microburst can result in strong downward winds (40 kt can be reached)
- The outburst of a microburst can result in both a large horizontal windshear and a wind component shift from headwind to tailwind (horizontal winds can reach up to 40 kt).
An aircraft that approaches a
microburst will first encounter a strong headwind. This can result in an increase in the indicated airspeed. This may cause the aircraft to fly above the intended flight path and/or accelerate. With a fixed speed on approach, the flight crew’s reaction may be to reduce power. This will cause the aircraft to fly with reduced energy through the downburst. The wind will then become a tailwind. The indicated airspeed and lift will drop and the downburst may be sufficiently strong to force the aircraft to lose a significant amount of altitude. The degraded performance, combined with a tailwind encounter, may cause the aircraft to stall.
AWARENESS AND AVOIDANCE
Awareness of the weather conditions that cause windshear will reduce the risk of an encounter. Studying meteorological reports and listening to tower reports will help the flight crew to assess the weather conditions that are to be expected during takeoff or landing.
If a windshear encounter is likely, the takeoff or landing should be delayed until the conditions improve, e.g. until a thunderstorm has moved away from the airport.
And
When the airshaft of a microburst reaches the ground, it mushrooms outward carrying with it a large number of falling rain droplets. The radar can measure speed variations of the droplets, and as a result, assess wind variations. This predictive capability to assess wind variations is performed by the Predictive Windshear System (PWS). The PWS automatically operates below a given altitude (Refer to FCOM/DSC-34-SURV-30-20 General), if the radar is ON or OFF, provided that the PWS sw is in the AUTO position.