Originally Posted by
HkCaGu
According to the analysis of AA pilot Juan Browne (YouTube video "0UYNFthOx1o"), a strong thunderstorm cell can block the signal of another cell behind it because strong radar beam reflections reduces the signal from behind. (Just look at any strong typhoon/hurricane/TC offshore on radar and you'll notice.) The second cell on the eastern half of the Burmese peninsula that SQ321 went through was apparently what caused this incident. So (1) I don't think the pilots had considerable notice, (2) any Burmese ground weather radar data go into the cockpit, (3) Burmese ATC would suggest routings. Nowadays geostationary weather satellites scan speed can outperform ground radars, and the aviation industry should improve data availability so they don't need onboard radar to see the rapidly developing second cell behind the first.
They certainly saw the line of weather with multiple cells from way out. They had plenty of notice provided by the first cell to lock everyone down. What Juan is describing is when you are trying to pick your way through a line of convective weather. There are also simple techniques to tell if a return is being attenuated.