The 2018 hurricane season: people need to be prepared
For the 2018 hurricane season in the North Atlantic basin, the number of hurricanes is expected to be close to the long-term average of 6.3, and therefore lower than the actual number of hurricanes in the previous year, according to the latest forecasts from various institutes. However, anyone hoping for a respite after last year’s devastating storms should note: even a single severe cyclone can cause extreme losses if it hits a heavily populated conurbation with full force.
A variety of climatic conditions influence hurricane activity
The year 2017 illustrated just how difficult it is to make accurate seasonal hurricane forecasts during the spring. Last year, leading forecast experts were anticipating a hurricane season that would be slightly below average due to the expected development of weak El Niño conditions later in the year. El Niño conditions are associated with increased vertical wind shear, i.e. the difference in wind speed and direction aloft and at the ocean’s surface, particularly over the Gulf of Mexico and Caribbean Sea. Since increased shear hinders hurricane formation and development, the expectation of El Niño conditions later in the year reduced the seasonal forecast. But as the summer of 2017 progressed, climatic conditions and the associated forecasts changed, and El Niño conditions ultimately did not develop during the peak hurricane months of August to October. As a consequence, hurricane formation during the peak hurricane season was not suppressed by this climate mode.
Anomalously high sea surface temperatures were also an important factor in the development of 17 named storms and 10 hurricanes in 2017 (average since 1950: 11.6 and 6.3 respectively).
Major hurricanes Harvey, Irma and Maria drove overall losses from the 2017 hurricane season to a record US$ 220bn, with US$ 90bn in insured losses.
Sea surface temperatures in the North Atlantic expected to be lower in 2018
While El Niño conditions normally reduce hurricane activity in the North Atlantic, the neutral conditions expected for 2018 mean that there are no specific effects that either reduce or promote the development of storms. This makes the forecast in neutral years especially difficult because the range of variation is high. For example, the very active and devastating seasons of 2005 and 2017 occurred under neutral-to- weak La Niña conditions.
What does all this mean for the 2018 hurricane season? For US states and the other countries bordering the northwestern Atlantic, Gulf of Mexico and the Caribbean Sea, the current background conditions send the following message: these regions should prepare for a normal tropical storm season with the possibility of a hurricane or even a major hurricane hit in their territory – just as they always should given that it only takes one storm to wreak major destruction.