What is the purpose of USA warning Russia about missile strikes in Syria?
According to this article, the US warned the Russians ahead of Syria missile strikes. It does not specify when exactly this occurred (a few minutes means nothing, 1-2 hours means that some troops/planes can be moved from the target area).
This article tells us about the Russian Growler anti-missile defense system that theoretically could be used against the tomahawks:
Russians have one of their self-proclaimed state of the art Growler anti-missile defense systems on Latakia Airbase on the Syrian coast. The Growler has reportedly been able to intercept targets at a range of 250 miles and at heights of up to 90,000 feet.
Question: what is the reason to make such a warning? From a military perspective, it does not make any sense. So, I suspect a political reason.
Russia was warned because there is a Russian military presence at the base.
Airbus Defence & Space satellite imagery shows that there were four [Russian] Ka-52 Alligator and three Mi-28N Night Hunter helicopters deployed to Al-Shayrat Air Base, 30 km southeast of Homs city, on 31 March. Al-Shayrat has previously been used as a forward base for Russian Mi-24 and Mi-35 helicopters, four of which could be seen at the base on 31 March. (Source: Jane's Defence Weekly)
[T]he Americans told Moscow in advance about the strike, to avoid casualties among Russian military personnel stationed on the airbase (source: BBC)
Sources have told the Guardian that US intelligence officials believe Russian personnel were at al-Shayrat airbase when sarin was loaded on to a Syrian jet. They have not established whether the Russians knew it was happening. (source: The Guardian)
Killing Russian personnel could lead to a huge escalation.