Storm, looking for his first European Tour title in more than five years and his second overall, shot a 4-under-par 66 and moved to 11-under 129 after 36 holes.
Storm had a birdie at the third hole and was still one-under through 10 holes. He added a birdie at 11 and also had birdies at 15 and 18.
Jamieson had an eagle, five birdies and a bogey in matching in the best round of the day at 6-under 64. Fernandez-Castano had an eagle, four birdies and a bogey in shooting 65 and Hanson had an eagle and two birdies in a bogey-free 66.
All three of the eagles came at the 484-yard par-5 12th hole, which yielded 18 eagles and 164 birdies through two rounds.