The correct answer is option 3: rapid withdrawal of water away from the beach. This can be considered an initial warning sign of an approaching tsunami.

Let`s dissect each option to better understand why option 3 is the correct answer:

1. Thundering noise: While a tsunami can generate loud noises, such as the crashing of waves, this is not an initial warning sign. By the time the noise reaches the shore, the tsunami is already near.

2. Squally winds and rainfall: Strong winds and heavy rainfall can be a sign of an impending storm but may not necessarily indicate a tsunami. Tsunamis are not typically associated with these weather conditions.

3. Rapid withdrawal of water away from the beach: This is a key warning sign of a tsunami. When a tsunami approaches, it causes the water to recede rapidly from the shore, exposing the ocean floor. This is due to the vast amount of water being pulled back as the wave approaches.

4. Rapid landward movement of water: While tsunamis do cause a rapid movement of water, it is typically away from the shore, not towards it. So, option 4 is incorrect.

Therefore, the correct answer is option 3: rapid withdrawal of water away from the beach.