An ERJ170 crew flew into a thunderstorm while on an ATC vector; but did not see the weather visually or on radar even though ATC pointed it out prior the severe turbulence and precipitation encounter.

Narrative

The First Officer was in the lavatory when I received the clearance to turn to a new heading and start a descent from 14;000 to 11;000 FT. ATC advised me of some cells in the direction of the turn; so I looked visually and on RADAR and could not see any concerns in our intended path. The First Officer came back into the cockpit and I transferred controls to him with a briefing of the new heading/altitude. Neither of us saw concerns with the new flight path. As we were leveling at 11;000 FT we were enclosed by severe precipitation with no available turn that would have improved the situation. We proceeded straight which appeared to be the best route out of the precipitation. Shortly after entering the precipitation we lost IAS; autopilot; and multiple flight control faults appeared. ATC contacted us about the altitude deviation and I responded at that time we were level at 11;000 FT; but we were in some weather that needed my immediate attention and I would call him back in a minute. We experienced severe turbulence in the precipitation. We did not see this weather visually or on radar as we made the turn and descent. I called ATC back as soon as we cleared the severe weather and we continued the flight without further problems. I contacted Maintenance to inform them of the weather the aircraft was flown through. It was helpful of ATC trying to advise us of the precipitation; but we were unable to see it either visually or on RADAR. If ATC believes severe weather to be near our flight path during a turn or descent; [they should] possibly try and vector us away from it as opposed to toward it. Our RADAR takes time to catch up with the new flight path to detect weather on that route.