The eastern half of the U.S. and the Caribbean lucked out last year with a below-average Atlantic hurricane season.
This year, we’re back to “average,” say forecasters. That means a total of 12 named storms, five hurricanes and two major hurricanes. But it’s not that simple. Weather Underground called the forecast “uncertain,” and here’s why:
The “El Niño” weather pattern kept hurricanes at bay in 2015, but it is expected to die out sometime in the spring or early summer.
“La Niña” often, but not always, follows El Niño.
Computer models are forecasting the development of a strong La Niña, which could ring in a higher number of hurricanes.
Hurricanes in Yucatán, when they happen, often come in from the Caribbean, then head north along the Atlantic coast of the U.S.
So yesterday, NOAA issued a “La Niña Watch” for late summer or early fall. If it does materialize, it would mean the Atlantic would have weaker wind shear and give hurricanes an easier time forming.
The nerdy details from NOAA:
During La Niña, the area of tropical convection and its Hadley circulation is retracted westward to the western Pacific and Indonesia, and the equatorial Walker circulation is enhanced. Convection is typically absent across the eastern half of the equatorial Pacific.
In the upper atmosphere, these conditions produce an amplified trough over the subtropical Pacific in the area north of the suppressed convection, and a downstream ridge over the Caribbean Sea and western tropical Atlantic. Over the central and eastern subtropical Pacific, the enhanced trough is associated with stronger upper-level winds and stronger vertical wind shear, which suppress hurricane activity. Over the Atlantic basin, the anomalous upper-level ridge is associated with weaker upper- and lower- level winds, both of which reduce the vertical wind shear and increased hurricane activity. La Niña also favors increased Atlantic hurricane activity by decreasing the amount of sinking motion and decreasing the atmospheric stability.
The Atlantic hurricane season officially starts on June 1 and last through Nov. 30, although one hurricane already formed in January. That’s when Hurricane Alex became one of the earliest hurricanes ever recorded in the Atlantic and made landfall as a tropical storm on the Azores islands near Portugal.
Last year, forecasters correctly predicted a light hurricane season for 2015.