Why the Atlantic Hurricane Season Is So Different Right Now Compared to a Year Ago

In mid-August last year, we were in the beginning stages of a period that would yield 10 consecutive hurricanes in the Atlantic basin and last until mid-October. Fast-forward a year later and the Atlantic is mostly quiet, devoid of any major areas of stormy weather.

Here are three ways the Atlantic looks different than it did a year ago.

(MORE: Hurricane Central)

Satellite Image Comparison

We can assess the difference in the Atlantic between mid-August 2017 and 2018 by looking at one of the most basic tools meteorologists use: satellite imagery.

A year ago Thursday, Aug. 16, Hurricane Gert was well off the U.S. East Coast and several other tropical disturbances were lined up across the Atlantic. One of those disturbances would become Hurricane Harvey several days later.

In its tropical weather outlook issued on the afternoon of Aug. 16, 2017, the National Hurricane Center was tracking Gert and was monitoring three other systems for development.

This year, the tropical Atlantic couldn't look much quieter on satellite imagery.

There are some seeds for tropical storm development called tropical waves in the Atlantic now, but they are poorly organized and not producing much shower and thunderstorm activity.

A moist atmosphere is needed for tropical waves to have concentrated shower and thunderstorm activity, which helps them perk up and become organized tropical storms or hurricanes.

Cooler Sea-Surface Temperatures 

Sea-surface temperatures (SSTs) in the tropical Atlantic are colder now compared to a year ago.

In early August 2017, the SSTs in the Atlantic were solidly above average, providing a boost for tropical disturbances to grow into tropical storms and hurricanes.

This year, water temperatures in the tropical Atlantic are cooler overall, with some areas running a bit below average for the first part of August. Cooler waters can deter the development of tropical storms and hurricanes.

The animation below compares widespread above-average water temperatures in the Atlantic Aug. 10, 2017, to near or even below-average water temperatures Aug. 9, 2018.

As of Monday, SSTs as a whole are running just below average in the main development region (MDR) of the Atlantic, according to analysis from tropicaltidbits.com. The MDR is a swath of the tropical Atlantic Ocean that stretches from Africa's western coast into the Caribbean.

Stronger Wind Shear

When wind shear is strong, it can keep tropical storms from forming and can rip apart existing storms. Strong wind shear means winds strongly change with height, either in speed and/or direction.

In the first 10 days of August 2017, wind shear was below average in a swath from the western Gulf of Mexico through the Caribbean and into parts of the tropical Atlantic. The lower wind shear helped aid in the active 2017 hurricane season.

In the first 10 days of August this year, there's been a greater than average amount of wind shear from the Gulf of Mexico to the Caribbean and the tropical Atlantic. Stronger wind shear in combination with dry air can be detrimental to the formation of tropical storms.

Of course, all of this does not mean we are off the hook for an impactful tropical storm or hurricane in the Caribbean or the United States in the peak of the season. It takes only one storm to produce major impacts and a memorable hurricane season.

Residents of coastal locations should have a hurricane preparedness plan in place every year no matter how active a season is projected to be.