Complex sentence: Upon becoming a tropical storm, the low-level circulation had become better defined, though forecasts predicted the wind shear would increase, preventing significant strengthening of the storm; one forecaster at the National Hurricane Center remarked the system resembled a subtropical cyclone.
Split into simpler sentences: Upon becoming a tropical storm, the low-level circulation had become better defined, though forecasts predicted the wind shear would increase, preventing significant strengthening of the storm. One forecaster at the National Hurricane Center remarked the system resembled a subtropical cyclone.