A method of applying a gas shielded tungsten arc welding process in a deep, narrow groove joint wherein the shield gas is directed to the weld puddle through an elongated gas nozzle 14 which surrounds a substantial length of the welding electrode and is sized to extend into the groove. The improvement including incrementally increasing the width (20) of the nozzle to correspond to increases in the width of the groove at preselected increases in the width of the groove as the nozzle is withdrawn from the groove during successive weld passes. The preselected elevations and nozzle widths are chosen so that the desired gas shield area does not substantially exceed 1.25 times the nozzle width.