Welcome to hurricane season, North America

Hurricane season in the Eastern Pacific officially started today at midnight GMT. Hurricane season begins in the Atlantic 16 days later, on June 1st. While 2005 definitely showed that it's not impossible for hurricanes to form outside of the designated season, "hurricane season" is just the window of time when the NHC feels it is prudent to keep staff on 24-hour watch for developing storms. Nothing as yet looks to threaten the North American mainland, and it's likely to stay that way for several weeks. The Eastern Pacific basin forms far fewer hurricanes that can threaten land, because hurricanes in the northern hemisphere tend to start out moving westward, and only recurve eastward after gaining latitude by venturing north. The currents in the Pacific keep the temperatures much lower than the Atlantic in the latitudes that are likely to see eastward-moving hurricanes. Thus most East Pacific hurricanes simply move harmlessly out to sea, which is what is likely to happen to any storm that may happen to form there in the next two weeks.

Meanwhile, Chanchu has turned northward towards Hong Kong, and is now a Super Typhoon with sustained winds of 155 miles per hour. The terms "Super Typhoon" and "Category 5 Hurricane" are almost, but not entirely synonymous. A "Super Typhoon" is defined to have sustained winds of 151 mph or higher. A hurricane becomes Category 5 with sustained winds of 156 mph or higher. Thus for now, Chanchu is in that narrow band of storms that are Category 4 Super Typhoons.