Hurricane season is off to a fast start.
With Hurricane Irma already a major hurricane — defined as a Category 3 or above storm by the National Hurricane Center — the 2017 Atlantic hurricane season has seen four hurricanes (two major ones, Harvey and Irma) and nine named storms before the start of September.
“We’re a way ahead of schedule for named storms,” Phil Klotzbach, a meteorologist at Colorado State University who specialises in Atlantic hurricane forecasts, told Business Insider.
Hurricane season doesn’t hit its peak until September 10 and normally, the average date of the fourth hurricane in a year is September 21.
“Typically, about 55% of hurricane activity occurs after September 1,” Michael Ventrice, a meteorological scientist at The Weather Company (the group behind the Weather Channel and Weather Underground) told Business Insider. “Everything is continuing to point to an active season.”
The Weather Company’s most recent updated forecast predicted 17 named storms, nine hurricanes, and said four of those would be major. CSU most recently predicted 16 named storms, eight hurricanes, and said three of those would be major.
“I think all in all, we’re still on track for an above-average season. The tropical Atlantic is warmer than normal right now, and vertical wind shear (the change in wind direction with height) has been pretty weak,” said Klotzbach. “It’s been a bit drier than normal which has tended to suppress storm activity in the deep tropics over the past few weeks, but that looks to be changing… just in time for Irma.”
Irma is making a long journey across the Atlantic that will test prediction science, according to Ventrice.
A number of models have Irma headed a bit further north than the Gulf, either pointed towards the East Coast or potentially turning away. But Ventrice said that “some of the better performing model’s that are correctly handling [Irma’s] initial formation are more favourable towards the Gulf of Mexico,” the region that has already suffered through Harvey.
“It could be the strongest hurricane of the year,” he said.
While conditions have been particularly favourable to hurricane formation recently, Ventrice said that wouldn’t necessarily remain the case throughout the season. The Weather Channel predicts a dip in activity right around the theoretical peak, sometime after Irma.
But even if that lull occurs and lasts for two to three weeks, he said “we could very well see another active period as we move towards the final week of September.”
By that point in time, Ventrice said he expected the conditions causing storms to form off the coast of Africa could come to an end, but we could see an uptick in storms forming in the Caribbean.
The climatological peak doesn’t mean it will always be the strongest time of year for storms just because it’s the annual average, he said. You might hit a lull then instead — but that doesn’t mean things are over.
Another measure that meteorologists use to track the force of storms we’ve experienced so far is accumulated cyclone energy (ACE), which takes into account the number of storms we’ve seen, how powerful they have been, and how long they lasted, according to Klotzbach. By that standard, 2017 has been fairly average so far, though he said that Irma could very quickly make it an “above average” year.
Since that measure usually jumps significantly after this point, Klotzbach said it’s an indication of more storms ahead.
“Since ACE is a function of frequency, intensity and duration, we’re also likely to see more major hurricanes yet to come this year,” he said.
#Irma is now a major hurricane – the 2nd of 2017 Atlantic hurricane season & the first time since 2010 we’ve had 2 major hurricanes by 8/31. pic.twitter.com/RwPq9hrj1B
— Philip Klotzbach (@philklotzbach) August 31, 2017
Through Aug. 30, Atlantic Accumulated Cyclone Energy in 2017 is near long-term average. Looks like it could jump significantly with #Irma pic.twitter.com/JQWN1Zd67e
— Philip Klotzbach (@philklotzbach) August 30, 2017
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