The nation's hurricane forecasters have some good news about this year's projected Atlantic storm season—though they say coastal residents shouldn't drop their guard just yet.
On Thursday, the National Oceanic and Atmospheric Administration downgraded its forecast for the Atlantic hurricane season. Instead of the near- or above-normal season that NOAA projected back in May, they now expect a below-normal year thanks to cool ocean temperatures in parts of the Atlantic and the expected formation of El Niño.
"What's fascinating is if you look at March of last year and you look at March of this year, the Atlantic in both years looked super similar," said Phil Klotzbach, an atmospheric scientist at Colorado State University who studies hurricanes. But whereas the spring of 2017 created the conditions for a vicious—and deadly and costly—storm season, the opposite has happened this year.
"Back in May, the models were predicting that the temperatures would warm up maybe to near average," said Gerry Bell, NOAA's lead seasonal hurricane forecaster. That prediction led to an early forecast that saw a 35 percent chance of an above-normal season, with between 10 and 16 named storms and up to four major hurricanes.
Instead, the critical part of the Atlantic Ocean off Western Africa where major storms form has stayed cooler than usual. And NOAA is also now projecting a 70 percent chance that El Niño conditions will develop during hurricane season. "The climate models are in good agreement that if it develops, it will be strong enough to suppress the later part of the hurricane season," Bell said.
El Niño forms when ocean temperatures in the eastern half of the tropical Pacific Ocean are warmer than average. That alters tropical rainfall patterns, which in turn alters wind patterns in the upper atmosphere, which can suppress Atlantic hurricanes, Bell explained.
It's a different story in the Pacific, though, where there have already been 11 named storms. El Niño conditions can strengthen storms in the eastern and central Pacific.
This might seem like good news along the Atlantic, but Bell cautioned that just because NOAA is downgrading its forecast for the hurricane season doesn't mean there's nothing to worry about. Hurricane Andrew, for example, devastated parts of Florida during an otherwise quiet 1992 season. "There will be more hurricanes—that's just a fact," he said.
So far, this hurricane season has seen four named storms—Alberto, Beryl, Chris and Debby, which is currently losing steam in the north Atlantic. NOAA is calling for 9 to 13 named storms before the season ends in November, with as many as two major hurricanes.
Alberto, a subtropical storm, dumped at least three inches of rain across six Southeast states, causing flooding and landslides in the Carolinas and sweeping away two vehicles in Virginia.
Hurricane Beryl brought heavy rain and damaging wind to the Virgin Islands, Puerto Rico and the Dominican Republic, but did not make landfall.
Last year was among the 10 most active Atlantic hurricane seasons on record. The NOAA animation above shows how sea surface temperatures off the U.S. coast rose though the summer that year ahead of a succession of deadly and destructive hurricanes.
Hurricane Harvey dumped as much as 60 inches of rain on parts of Texas—flooding large swaths of Houston—and tied 2005's Hurricane Katrina for costliest tropical cyclone on record. Hurricane Irma followed, breaking a world record when it held onto its peak intensity of 185 mph for 37 hours, and unleashing catastrophic destruction on the island of Barbuda, which had to be evacuated completely.
Then Hurricane Maria struck Puerto Rico, causing widespread electricity failures and road blockages that lingered for many months after the storm, stranding residents and hobbling emergency services. The territory's government acknowledged in a recent report to Congress that the death toll from the storm was over 1,400 people, far higher than its earlier count of 64.