It's TRW, not TWR. TWR might be an abreviation for Tower.
A TRW is a weather-related acronym that any pilot who has ever flown anywhere where it rains knows what it is. Or, he'd better.
It's a.....THUNDERSTORM W/ RAIN SHOWERS
Sometimes they're just shown as 'T'.
And if you don't respect them as a few have not, you will cause a fatal accident. Although, I hardly call it an accident if someone deliberately flies into one. Or, even NEAR one.
But.....we digress.