El Niño winds and warm Gulf waters vie to shape Hurricane Isaias as it nears US coast
In short
Hurricane Isaias, the ninth named storm of the Atlantic season, is heading for the U.S. Gulf Coast after a season in which a strong El Niño kept every previous named storm below hurricane strength. Colorado State University researcher Phil Klotzbach said El Niño's wind shear and the Gulf of Mexico's unusually warm water are competing over how strong the storm becomes.
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Hurricane Isaias, the ninth named storm of the Atlantic hurricane season, is approaching the U.S. Gulf Coast. PBS NewsHour reported that none of the previous named storms reached hurricane strength, after one of the strongest El Niño years on record kept the first four months of the season quiet. "The season has been completely dead — and we're still going to have an impactful storm hitting the northern Gulf," Colorado State University hurricane expert Phil Klotzbach said. "How impactful it is remains to be seen." [ 1 ]
Reports in The Seattle Times and ABC News described a contest between El Niño's winds and the Gulf of Mexico's warm waters over the storm's future strength. El Niño's wind patterns kept almost any storm from strengthening in the Atlantic this season, Klotzbach said. The effect, called wind shear, pushes the tops and middle of storms around, making them lopsided and keeping them from forming a complete circular eyewall, Klotzbach and Kristen Corbosiero of the University at Albany said. [ 3 , 4 ]
The Gulf of Mexico is about 2.7 degrees Fahrenheit (1.5 degrees Celsius) warmer than normal. Climate scientist Kristina Dahl, vice president of the nonprofit Climate Central, said the 86-degree (30 degrees Celsius) waters are 100 to 500 times more likely to be that hot because of climate change from the burning of coal, oil and gas. Klotzbach told PBS NewsHour the Gulf waters are "super hot" and "rocket fuel for hurricanes", and named the Madden-Julian Oscillation, a seasonal weather pattern, as another contributor. [ 1 , 3 , 4 ]
"But there's a certain point where it's like, I don't care how hot the waters are and how much moisture you have, if shear gets to a certain point, the shear is gonna win," Klotzbach said. Experts said the storm's precursor thunderstorms grew earlier in the week from circular winds over Central America but were often lopsided and could not form an eyewall because of El Niño's high-level winds, before a window of moderation opened for a couple of days. The Associated Press reported that Isaias found a brief window in El Niño to power up in extra warm water. [ 2 , 3 , 4 ]
Klotzbach said El Niño "still is certainly driving the bus" in the storm's formation and could become the strongest one ever recorded. Overall Atlantic hurricane activity, measured by the number, strength and duration of storms, is on track to be the quietest since modern data started around 1950, he said. A normal season has 14 named storms, seven of them hurricanes and three major hurricanes of more than 110 mph (177 kph), PBS NewsHour reported. [ 1 ]
Why it matters
Klotzbach said an impactful storm is still expected to hit the northern Gulf, though how impactful remains to be seen. The coverage also links the storm's fuel to climate change, citing Climate Central's estimate that the Gulf's current water temperatures are 100 to 500 times more likely because of global warming.
Key facts
- Isaias is the ninth named storm of the Atlantic season; none of the previous ones reached hurricane strength. [ 1 ]
- The Gulf of Mexico is about 2.7 degrees Fahrenheit (1.5 degrees Celsius) warmer than normal, with waters around 86 degrees (30 degrees Celsius). [ 3 , 4 ]
- Climate Central's Kristina Dahl said such water temperatures are 100 to 500 times more likely because of climate change from burning coal, oil and gas. [ 3 , 4 ]
- El Niño's wind shear makes storms lopsided and keeps them from forming a complete circular eyewall, Klotzbach and Kristen Corbosiero of the University at Albany said. [ 3 , 4 ]
- Overall Atlantic hurricane activity is on track to be the quietest since modern data started around 1950, Klotzbach said. [ 1 ]
- A normal season has 14 named storms, seven hurricanes and three major hurricanes, PBS NewsHour reported. [ 1 ]
Confirmed by several sources
Still unclear
- How strong Isaias will become before it reaches land. Reports describe an ongoing contest between El Niño's wind shear and the warm Gulf water, with no outcome stated.
- How severe the storm's impact on the northern Gulf will be. Klotzbach said how impactful it is "remains to be seen".
- Where and when Isaias will make landfall. None of the documents gives a landfall location or time.
What local media are saying
Timeline, local time
- October 8: PBS NewsHour reports on El Niño's role in Hurricane Isaias as the storm heads for the U.S. Gulf Coast. [ 1 ]
- October 9: The Associated Press reports that Isaias found a brief window in El Niño to power up in extra warm water. [ 2 ]
- October 9: The Seattle Times reports on El Niño's winds and warm Gulf waters battling over the storm's future strength. [ 3 ]
- October 9: ABC News carries the same account of the contest over Isaias's strength. [ 4 ]