There were ominous dark clouds gathering overhead.

不祥的阴霾在头顶上汇聚

Well, that's what I thought at first. "Stupid autocorrect", right? But then I got another ominous email from my sister.

我一开始也是这么想的，想着自动纠错真是蠢，对吧？但是后来，我又收到一封我姐姐发的邮件，很不吉利。

There were ominous dark clouds gathering overhead.

不祥的阴霾在头顶上汇聚。

There was an ominous silence at the other end of the phone.

电话那端是一阵不祥的沉默。

She picked up the phone but there was an ominous silence at the other end.

她拿起电话，但对方只有不祥的沉默。

The hooting of an owl came over the hill--ominous sound!

山那边传来猫头鹰的叫声——不吉利的声音！

This ominous warning soon proved prophetic.

这一不详的警示不久就证明有预见性。