ESL writing tips, #1: ‘in case’ or ‘if’?

The first in a (possible?) series of posts about issues that often crop up in the work of ESL (English as a Second Language) writers.
 
I recently found a sentence similar to this, in a research paper written by an ESL author:
 
In case a new best solution is found, the search begins again, based on this new solution.
 
The intended meaning of ‘In case’ was actually ‘If’, like this:
 
If a new best solution is found, the search begins again, based on this new solution.
 
What’s the difference? In UK English, there is a clear distinction: ‘if’ is used for a conditional statement, while ‘in case’ indicates something that is done as a precaution.
 
Let’s look at another example:
 
If it’s raining, I’ll take my umbrella.
 
This is conditional. It means I will check the weather before I leave; then, if it’s raining, I will take my umbrella. If it isn’t raining, I won’t take it.
 
Compare that with this:
 
I’ll take my umbrella, in case it starts raining later.
 
This means I’m being cautious: I’ll definitely take my umbrella, whatever the weather is like when I leave, because it might rain later.
 
In US English, ‘in case’ can mean the same as ‘if’, but this is quite unusual. To avoid confusion, whenever you mean ‘if’, it seems sensible to use that word.
 
By the way, if you do use ‘in case’ for either of these meanings, it must be two words: ‘incase’ is a variation of the verb ‘encase’, which is completely unrelated to all of this.