At a Glance

El Niño conditions are beginning to weaken and this trend is expected to continue.ENSO-neutral conditions are most likely this fall and winter.A lack of El Niño conditions could lead to a busier Atlantic hurricane season.

El Niño conditions appear to be weakening and this trend is expected to continue, which could result in a busier Atlantic hurricane season.

An remains in effect, according to the latest discussion from NOAA's Climate Prediction Center, but a transition to neutral conditions is expected in the next month or two and neutral conditions are most likely to persist through fall and winter.

Weak El Niño conditions have persisted the last few months and although above-average sea-surface temperatures were present in the central equatorial Pacific Ocean, water temperature anomalies decreased in the eastern equatorial Pacific in June, indicating a weakening El Niño.

Sea-surface temperature anomalies over the eastern equatorial Pacific as of early July.

El Niño conditions occur when average sea-surface temperatures in a are at least 0.5 degrees Celsius warmer than average than the previous month and last, or are expected to last, for three consecutive months.

ENSO-neutral conditions occur when neither El Niño or La Niña conditions are present. ENSO refers to the El Niño/Southern Oscillation, which is a climate pattern that looks at the sea-surface temperatures in the central and eastern Pacific and its interaction with the atmosphere.

The probability of El Niño (red bars) decreases and neutral conditions (gray bars) increases this fall and winter.

(NOAA)

What Does This Mean For Atlantic Hurricane Season?

ENSO conditions can impact tropical activity in the Atlantic and eastern Pacific due to its interactions with the atmosphere.

In general, wind shear, the change in wind direction and/or speed with height, is stronger in the Atlantic Basin in El Niño hurricane seasons. Wind shear tends to reduce the number of named storms and hurricanes. In addition, there is often more sinking air in portions of the Atlantic Basin in El Niño years. Sinking air is hostile to tropical cyclone development.

Conversely, when La Niña is observed, wind shear is stronger in the eastern Pacific, limiting the number of named storms and hurricanes. In addition, wind shear and instability tend to be more favorable for tropical development in parts of the Atlantic and Caribbean.

Water temperature and atmospheric changes over the eastern equatorial Pacific can influence the amount of wind shear, which is hostile to tropical development, in both the eastern Pacific and Atlantic.

Interestingly, in ENSO-neutral years, the number of named storms and hurricanes is similar to La Niña years, based on data from 1995 through 2016 from NOAA.

(MORE: Hurricane Season in July)

Tropical activity in La Nina and ENSO-neutral years tends to be above average, while El Niño hurricane seasons usually see a below-average number of named storms and hurricanes. The 30-year average is 12 named storms, 6 hurricanes and 3 major hurricanes ( or higher).

La Niña and ENSO-neutral years have generally seen more named storms and hurricanes in the Atlantic, based on data from 1995-2016.

(Data from NOAA/CPC)

Current forecasts for the Atlantic hurricane season suggest a near or slightly-above average season. Most forecasts expected weak El Niño conditions to remain in place at the peak of hurricane season, in late August and September.

If ENSO-neutral conditions have developed by late August, it could increase the chance for a busier Atlantic hurricane season and a quieter-than-average eastern Pacific hurricane season.

However, factors other than wind shear influence hurricane activity. These include water temperatures, the number of tropical waves off Africa and how much dry air comes into the Atlantic from the Sahara.