The Atlantic hurricane season officially began on June 1, 2018, and ends on November 30, 2018. Ahead of and during the season, several national meteorological services and scientific agencies forecast how many named storms, hurricanes, and major hurricanes (Category 3 or higher on the Saffir-Simpson scale) will form during the season and/or how many tropical cyclones will affect a particular country. These agencies include the Tropical Storm Risk (TSR) Consortium of University College London, the National Oceanic and Atmospheric Administration (NOAA), and Colorado State University (CSU).
Some of these forecasts take into consideration what happened in previous seasons and an ongoing La Niña event that had recently formed in November 2017, although the cooler waters of the eastern equatorial Pacific Ocean, the oceanic signal for La Niña, are continuing to fade and the Climate Prediction Center expects neutral conditions — neither La Niña nor El Niño — by this summer.
An important factor to keep in mind is the Atlantic Ocean Temperature Pattern. Indeed, during the April/May month, a pattern of cooler-than-average water temperatures has developed in the eastern Atlantic and, to a lesser extent, in the central northern Atlantic. Temperatures in the space between the Lesser Antilles and Africa are supportive for tropical growth nearly year-round, but the warmer the water in that region, the more likely a tropical cyclone is to develop there, all other factors (wind shear, atmospheric moisture, forward speed, etc.) held constant. Should this pattern of cooler-than-average ocean temperatures continue into the heart of hurricane season (August, September, and October), we can expect less tropical activity west of Africa.
Another important factor is the increasing North Atlantic Oscillation (NAO), which is defined as a pattern of pressure gradients over the northern Atlantic Ocean. The NAO was expected to trend slightly positive through much of the spring. Both the Azores-Bermuda high-pressure system and the Greenland low-pressure system are strengthened in the positive phase of the NAO. This creates a stronger pressure gradient and increased wind between the two systems. This also creates more wind around the Azores-Bermuda high. In the winter, this means a quicker storm track for winter storms crossing the northern Atlantic, but in the hurricane season it may bring a few less-than-favorable conditions for hurricanes:
• Gustier winds across much of the subtropics and North Atlantic.
• Cooler water temperatures.
• A slightly faster tropical wave track across the Atlantic.
• The positive phase of the NAO decreases the chances of an active year.
On April 5, 2018, Colorado State University released its forecast, predicting a slightly above-average season with 14 named storms, seven hurricanes, and three major hurricanes. On the same day, Tropical Storm Risk (TSR) Consortium of University College London released a forecast predicting a slightly-below average hurricane season, with 12 named storms, six hurricanes, and two major hurricanes, reducing in both the number and size of storms compared to its first forecast due to recent anomalous cooling in the far northern and tropical Atlantic. Several days later, on April 16, North Carolina State University released its predictions, forecasting an above-average season, with 14–18 named storms, 7–11 hurricanes, and 3–5 major hurricanes. On April 19, The Weather Company released its first forecasts, predicting 2018 to be a near-average season, with a total of 13 named storms, seven hurricanes, and two major hurricanes.