The Atlantic hurricane season, which experts have warned is likely to have an above-average number of storms, has gotten off to a quiet start. Not a single tropical storm has formed since the season began on June 1.
That is typical.
The exact date of the first named Atlantic storm varies, and in nearly half of the last 20 years, it has arrived even before June 1. But on average, it forms around June 20; last year, Alberto formed on June 19. In 2009, it wasn’t until Aug. 11 that the first storm, Ana, finally appeared.
But one usually arrives before the end of the month, and Phil Klotzbach, a hurricane expert at Colorado State University, said it was unclear when this year’s first storm would form.
Here’s a look at what’s going on.
A storm gets a name when its sustained winds reach 39 miles per hour, and it becomes a Category 1 hurricane when they reach 74 m.p.h.
A key ingredient for that is warm ocean waters, with temperatures at 80 degrees or above, and Jason Dunion, a meteorologist with the National Oceanic and Atmospheric Administration, said many locations across the Atlantic had not quite reached that threshold.
“The waters are still warming, and they’re actually a little bit cooler than last year, so we’re not seeing some of those record temperatures,” Mr. Dunion said. Sea surface temperatures set records last year, which also made hurricanes more likely to rapidly intensify and become more destructive.
Saharan dust carried from North Africa is another factor. It travels far across the Atlantic Ocean, creating a layer of dry air in the atmosphere that can suppress storm development. Mr. Dunion described the layer as a combination of “superdry air that inhibits clouds, warm air that helps put a lid on clouds and thunderstorm development, and a strong jet of winds that acts to tilt and tear thunderstorms apart.”
This week, a plume of dust spread from the central Atlantic all the way through the Caribbean, for more than 2,500 miles, which is roughly distance between Washington, D.C., and San Francisco.
“It’s huge,” said Mr. Dunion, adding that conditions in large portions of the Atlantic just weren’t favorable for hurricanes right now because of the dust plume.
The season for trans-Atlantic dust begins in June and tapers off in mid-August, just as hurricane activity usually picks up. Mr. Dunion calls mid-August the “switch point.”
Dr. Klotzbach said wind shear had also been thwarting the formation of storms in the Gulf of Mexico, where tropical storms often form at this point in the season. Wind shear is the change of wind speed and direction with height, and it is notorious for shredding apart hurricanes and keeping tropical storms from developing.
Like NOAA, Dr. Klotzbach’s team at Colorado State released a forecast this spring that predicted an above-average number of storms this year. But if the shear remains elevated for several more weeks, he said, he may scale back his forecast “substantially.” On Wednesday, Dr. Klotzbach’s team issued an update saying that, for now, it was standing by its earlier expectation.
In a typical season, there are 14 named storms. NOAA has predicted between 13 and 19 this year; Dr. Klotzbach’s team expects there to be 17.
If the storm shear in the Gulf were to weaken and a storm were to move through the Caribbean or the Gulf, “we certainly have plenty of fuel there to get a robust hurricane,” Dr. Klotzbach said.
In the Eastern Pacific, where hurricane season began on May 15 and where storms typically form before they do in the Atlantic, has been off to a busy start. Three storms have already formed off the west coast of North America: Alvin, Barbara and Cosme. Both seasons run through Nov. 30.
Amy Graff is a Times reporter covering weather, wildfires and earthquakes.
Judson Jones is a meteorologist and reporter for The Times who forecasts and covers extreme weather.
The post Hurricane Season Started Two Weeks Ago. Where Are the Storms? appeared first on New York Times.
