"highly alert" is a correct and usable part of a sentence in written English.
You can use it to describe someone or something that is paying close attention to their surroundings. For example: The guard was highly alert, carefully scanning the area for any signs of trouble.
The thing is that you are highly alert.
They are each highly alert to the ironic possibilities of personal encounters.
And the French are highly alert to terrorism in the Maghreb, even after Osama bin Laden's death.
But the other part is highly alert and reactive, constantly moving toward new ideas and devouring them.
Given Hong Kong's awkward political situation as a semi-democratic oasis in a Communist country, he said, people here should be highly alert to any threats.
In particular, I've found the great majority of Muslim activists highly alert to the question of anti-semitism, keen to engage in dialogue with Jews and well aware that anti-semitism and Islamophobia are drawn from the same template.
"While physical security measures can play a role in an overall comprehensive school safety program, the first and best line of defense is a well-trained, highly-alert school staff and student body," said Kenneth Trump, president of National School Safety and Security Services.
Because Mr. Romney has the strong backing of the Republican Party establishment — and because he has highly capable and alert spokesmen — the news is unlikely to affect him as much as it might a candidate who relied more exclusively on media-driven momentum.
'Incorrect' alerts or 'missed' alerts were highly predictive of the next observation set, suggesting that work is needed to understand what additional information clinical staff use to 'outperform' the early warning system.
It is a highly innovative use of alert technology that will give you the up-to-date information whenever you pick up your phone.
And it is a pleasure to hear Wagner sung by highly intelligent musicians, impressively alert to rhythmic values, accents and dynamics.
