What is known is that the pilot requested to avoid bad thunderstorms by climbing over them. Other aircraft already occupied that part of the sky so permission was correctly refused. The plane then flew into the thunderstorm and was lost two minutes later. It would appear that there is a connection between the bad weather and the loss of the plane but no proof. It is possible to avoid bad storms by climbing, by using on board radar to avoid the worst parts of the storm, but also by turning away from them and not entering them in the first place. This may even result in a diversion to another airport - I have done it myself but a long delay is preferable to entering a severe storm. The real cause must remain surmise until the black boxes are recovered which should be possible in the shallow waters there.