Air carrier Captain reported a sharp acrid odor during cruise. After conferring with Dispatch the odor was determined to be caused by a volcanic ash event which was remedied by climbing to a higher altitude.

Narrative

At FL390 near waypoint ZZZ we encountered what looked like high cirrus clouds. Shortly after entering the IMC conditions we had a sharp acrid smell and suspected Volcanic ash as dispatch gave us a VA warning for FL 240 and below. We immediately made a left turn 15 miles off course and a climb to FL410. Once we reached FL 410 we were in the clear and the smell. went away. Notified ATC and dispatch of the encounter and wrote up airplane for VA encounter... Not much we could have done differently in my opinion there was a large Thunderstorm tomorrow right that was probably picking up the VA cloud and bringing it to altitude. We couldn't see the cloud/ ash to avoid it until we were in it. Again Dispatch did amazing job keeping us informed of the ash cloud that was well to our south and below us. We planned our descent to remain higher to avoid ash cloud on the arrival. Just can't predict mother nature.