Complex sentence: The depression was in an unusually low-shear environment for early June as it began tracking northward, which allowed the system to strengthen into Tropical Storm Allison on the morning of June 3 as it tracked into the Yucatan Channel.
Split into simpler sentences: The depression was in an unusually low-shear environment for early June as it began tracking northward. That allowed the system to strengthen into Tropical Storm Allison on the morning of June 3 as it tracked into the Yucatan Channel.