Colorado State University(CSU) hurricane researchers are predicting a slightly above-average Atlantic hurricane season in 2018, citing the relatively low likelihood of a significant El Niño as a primary factor.
Dr. Philip Klotzbach of Colorado State University (CSU) has issued his April forecast for the 2018 Atlantic Hurricane Season. The forecast calls for 14 named storms, 7 hurricanes and 3 major (Category 3+) hurricanes between the months of June and November.
With the release of the forecast, Dr. Klotzbach is predicting slightly above average tropical cyclone activity in the Atlantic Basin during the upcoming 2018 season. The report cites several factors as to why slightly increased activity is being forecast.
One such main factor regards the eventual transition of ENSO (El Niño-Southern Oscillation) from current La Niña conditions to ENSO-neutral. Sea surface temperatures over the tropical Pacific have been warming since November 2017 and upper-ocean heat content is currently above normal.
The statistical and dynamical forecast models continue to show a wide range of outcomes regarding the state of ENSO by the peak development months (August, September, October).
Roughly one-third of the models are calling for ENSO-neutral conditions by late summer/fall, with the rest of the model suite forecasting a weak El Niño. CSU’s best guess estimate at this time is that ENSO-neutral conditions will be present by the peak of the Atlantic hurricane season.
A second factor revolves around current sea surface temperatures across the North Atlantic Ocean. At present, there are cold anomalies in the far North Atlantic, near-normal temperatures in the eastern tropical Atlantic, and warm anomalies off the east coast of the United States.
Dr. Klotzbach says that this type of pattern is a mixture of signals typically seen in both a positive (warm) and negative (cool) phase of the Atlantic Multidecadal Oscillation (AMO). Much of the cooling can be attributed to a strong positive phase of the North Atlantic Oscillation (NAO) that allowed strong trade winds to cause increased mixing, upwelling, and evaporation. However, the pattern changed around March 1, and slight warming has since commenced as the NAO shifted negative.
Tropical Storm Risk (TSR) Atlantic Hurricane Season Forecast
Tropical Storm Risk (TSR), which is part of Aon Benfield Research’s academic and industry collaboration, has issued its April forecast for the 2018 Atlantic Hurricane Season. TSR’s Professor Mark Saunders and Dr. Adam Lea are forecasting 12 named storms, 6 hurricanes and 2 major (Category 3+) hurricanes between the months of June and November. This is a reduction from TSR’s initial projection of tropical activity released in December 2017.
The projected activity is expected to be 15 percent below both the long-range norm since 1950 and the recent 2008-2017 norm. The report specifies two primary factors as to why a slightly below normal hurricane season is now being forecast. The main reason is that TSR now expects ENSO-neutral conditions to be present by the summer and/or autumn of 2018.
This is in line with current consensus ENSO outlooks by both the dynamical and statistical models. Due to this expectation, TSR notes that this will have an increasing effect of stronger trade winds over the Caribbean Sea and tropical North Atlantic from the July to September time period.