Unexpectable/unexpected/unexpecting difference

[kiann]

While annual vacation days are limited to 10 days per day,employees facing unexpectable/unexpected/unexpecting situations may be granted leave.

Unexpectable/unexpected/unexpectingd have few differences, but in this sentence I don't know how to choose.
I think each one are acceptable. Please someone help me choose the best answer.

 

[tedmc]

I would choose 'unexpected'.
'Unforseen circumstances' and 'exigent circumstances' are more common.
Also, 'annual leave' is more common when we talk about conditions of employment, than 'annual vacation days'.

not a teacher

 

[kiann]

I would choose 'unexpected'.
'Unforseen circumstances' and 'exigent circumstances' are more common.
Also, 'annual leave' is more common when we talk about conditions of employment, than 'annual vacation days'.

not a teacher

I don't know whether they have difference in grammar or not.
Because they are all adjective and few differences, I think they are a common expression.

 

[MikeNewYork]

Only "unexpected" would be common in that use.

 

[kiann]

Only "unexpected" would be common in that use.

Why? Are there any different among them?

 

[bhaisahab]

Why? Are there any different among them?

Only "unexpected" is natural English in that context. In fact "unexpecting" is more than unnatural, it's wrong.

 

[Matthew Wai]

Are there any different among them?

I found a difference: 'unexpected' can be found on the following dictionaries but 'unexpectable' and 'unexpecting' cannot.
http://www.thefreedictionary.com/
http://dictionary.cambridge.org/
http://www.macmillandictionary.com/
http://www.ldoceonline.com/

Not a teacher.

 

[Rover_KE]

[STRIKE]Are there any different among them?[/STRIKE]

Is there any difference between them?

`

 

[SoothingDave]

I would choose 'unexpected'.
'Unforseen circumstances' and 'exigent circumstances' are more common.
Also, 'annual leave' is more common when we talk about conditions of employment, than 'annual vacation days'.

not a teacher

It's more normal in the US to speak of "vacation days" than "leave."