The helicopter was on a scheduled platform support flight from Cork Airport (EICK) to Platforms Alpha and Bravo in the Kinsale Gas Field. Following a rotors running passenger drop on Platform Bravo, the helicopter was subjected to intense squall activity, which necessitated the pilot flying (PF) initially inputting a roll correction, and then approximately 1 second later applying collective and lifting the helicopter airborne. With only limited visual clues available, due to the intensity of rain and hail, the PF fought to retain control of the helicopter, while in close proximity to the deck. The helicopter was then flown out of the squall and back to Cork Airport. A subsequent technical inspection determined that the helicopter gearbox had been slightly over-torqued. There were no injuries. This Report makes two Safety Recommendations.