A rare double feature: two simultaneous Category 4 hurricanes in the Atlantic, for only the second time in recorded history, 15 September 2010. wunderground.com / climateprogress.org

By Joe Romm
September 16, 2010 Uber-meteorologist and former NOAA Hurricane Hunter (!) discussed some of the remarkable records the 2010 season has already set, on his WunderBlog yesterday:

The Atlantic hurricane season of 2010 kicked into high gear this morning, with the landfall of Tropical Storm Karl in Mexico, and the simultaneous presence of two Category 4 hurricanes in the Atlantic, Igor and Julia. Tropical Storm Karl’s formation yesterday marked the fifth earliest date that an eleventh named storm of the season has formed. The only years more active this early in the season were 2005, 1995, 1936 and 1933. This morning’s unexpected intensification of Hurricane Julia into a Category 4 storm with 135 mph winds has set a new record–Julia is now the strongest hurricane on record so far east. When one considers that earlier this year, Hurricane Earl became the fourth strongest hurricane so far north, it appears that this year’s record SSTs [sea surface temperatures] have significantly expanded the area over which major hurricanes can exist over the Atlantic. This morning is just the second time in recorded history that two simultaneous Category 4 or stronger storms have occurred in the Atlantic. The only other occurrence was on 06 UTC September 16, 1926, when the Great Miami Hurricane and Hurricane Four were both Category 4 storms for a six-hour period. The were also two years, 1999 and 1958, when we missed having two simultaneous Category 4 hurricanes by six hours. Julia’s ascension to Category 4 status makes it the 4th Category 4 storm of the year. Only two other seasons have had as many as five Category 4 or stronger storms (2005 and 1999), so 2010 ranks in 3rd place in this statistic. This year is also the earliest a fourth Category 4 or stronger storm has formed (though the fourth Category 4 of 1999, Hurricane Gert, formed just 3 hours later on today’s date in 1999.) We’ve also had four Cat 4+ storms in just twenty days, which beats the previous record for shortest time span for four Cat 4+ storms to appear. The previous record was 1999, 24 days.

I don’t think there is much question that in the North Atlantic we’re going to see more intense hurricanes as humans keep warming the planet (see “Nature: Hurricanes ARE getting fiercer — and it’s going to get much worse“). …

Masters: “It appears that this year’s record [sea surface temperatures] have significantly expanded the area over which major hurricanes can exist over the Atlantic.”