I also noticed the typo as an intriguing detail, that's a good observation and read.

You might also read it as on the "sun side" there will be subsidence.

That gives us a clue to probably time, the landslide may occur during the day time during the second half of the day when the sun is on the more western side of the island. La Plan is in a highly cardinal point orientation.

This might also help calculate landfall time and there is a chance people will be awake or awakening in the US and elsewhere on the CONTUS.