"...however, the watch was dropped when Ignacio weakened. However, Ignacio still brought high waves and light rainfall to the islands." You use however twice. You should find an alternative if possible.
"Continuing to rapidly intensify, Hurricane Ignacio moved west-northwest at 10 mph (16 km/h). Ignacio was upgraded into Category 2 status on the Saffir-Simpson Hurricane Scale (SSHS)." I think you could combine the two sentences, and state when Ignacio was upgraded.
"The hurricane held peak intensity for several hours, however, an upper trough northwest of the Hawaiian Islands was gradually approaching Ignacio." If you're starting a new paragraph, a good rule of thumb is to include the time the stated fact happened, regardless of whether or not it was stated at the end of the last.
"the watch was cancelled as Ignacio resumed weakening..." Did it weaken beforehand? Because you use Igancio, and to me it appears Ignacio strengthened and weakened, with not much in between.