Two of the most well known hurricane season forecast groups both released their preliminary April outlooks for the 2018 Atlantic hurricane season Thursday. Colorado State University (CSU), led by Dr. Philip J. Klotzbach and Michael M. Bell, as well as Tropical Storm Risk (TSR), led by Professor Mark Saunders and Dr. Adam Lea, released outlooks with very different predictions.  However, both of these groups believe that the upcoming hurricane season, which officially begins in only eight weeks, will be less active than last year.

Colorado State University’s Tropical Meteorology Project released their 2018 Atlantic hurricane season forecast at 9:00 AM CDT Thursday morning at the National Tropical Weather Conference. Their outlook predicts that the upcoming Atlantic hurricane season will see approximately 14 named storms, 7 hurricanes and 3 major hurricanes, with an estimated Accumulated Cyclone Energy (ACE) index of 130 units. This is slightly above the long term average calculated by CSU of 12 named storms, 6.5 hurricanes and 2 major hurricanes, and an ACE index of 92. CSU predicted slightly above average activity for two primary reasons. While they expect the current La Niña event to dissipate this spring, they do not anticipate a significant El Niño to be able to develop this summer or fall. They also based their forecast off warmer than normal sea surface temperatures over the western subtropical Atlantic and cooler than normal sea surface temperatures over the eastern tropical Atlantic and far North Atlantic. CSU also predicts a slightly above-average probability of a major (Category 3 or stronger) hurricane making landfall in the United States: 63%, compared to the long-term average of 52%. CSU also predicts a 52% chance for a major hurricane tracking into the Caribbean Sea, above the long-term average of 42%.

Britain-based Tropical Storm Risk (TSR), in contrast with CSU, predicts that the 2018 Atlantic hurricane season will have slightly below normal activity. TSR forecasts that 12 named storms, 6 hurricanes, and 2 major hurricanes will form over the Atlantic basin in 2018, with an approximate ACE index of 84 units. This is below TSR’s calculated long-term average of 11 named storms, 6 hurricanes, 3 major hurricanes, and an ACE index of 103 units. TSR estimates a 27% probability that the 2018 Atlantic hurricane season will feature above-normal activity (ACE > 119), a 33% probability of near normal activity (ACE 69 to 119), and a 40% probability of below normal activity (ACE < 69). This is lower than TSR’s forecast from December, in which they predicted 15 named storms, 7 hurricanes, 3 major hurricanes and an ACE index of 117. The primary reason for TSR lowering their forecast numbers is that the tropical Atlantic is now expected to have cooler than previously anticipated sea surface temperatures in August and September. They also predict that trade winds over the tropical Atlantic will be slightly stronger than normal, which could suppress activity over the Atlantic Main Development Region (MDR). TSR also predicts that the chance of tropical cyclone landfalls in the United States in 2018 will be slightly below average.

Recall that late last month, Cyclonic Fury released our preliminary 2018 Atlantic hurricane season forecast, in which we predicted 11-16 named storms, 5-9 hurricanes, 2-4 major hurricanes and an ACE of 125 +/- 50 units.

Last season, the April outlooks from both CSU and TSR turned out to be way too low. CSU predicted 11 named storms, 4 hurricanes, 2 major hurricanes and an ACE index of 75, while TSR predicted 11 named storms, 4 hurricanes, 2 major hurricanes and an ACE index of 63. The organizations both expected a weak to moderate El Niño event to develop, which never materialized. It should be stressed that the precision of all April hurricane season outlooks are low, primarily due to the ENSO Spring Predictability Barrier.

I will be back with another post next week discussing the retired and replacement names selected by the World Meteorological Organization (WMO). It is anticipated that the names Harvey, Irma, Maria and possibly Nate will be retired.