WeatherTiger’s August update to our 2018 hurricane season presents only minor changes from our initial forecast issued in late May for overall activity of between two-thirds and three-quarters of an average year. Cooler than average waters in key regions of the Atlantic, a developing El Niño in the Pacific, and much stronger than average trade winds in the Caribbean this summer confirm these signals.
Articles by Ryan Truchelut
The equatorial Pacific remains in a neutral-positive state. While atmospheric measures of ENSO state are slowly but steadily shifting towards Niño-like teleconnections, SST anomalies themselves cooled slightly over the past 6 weeks. This favors the slower development of a Central Pacific +ENSO event this fall.
The equatorial Pacific remains in a neutral state at present. However, atmospheric measures of ENSO state are beginning to tilt heavily towards Niño-like patterns. This trend is likely to intensify over the next six weeks as the Pacific flirts with weak El Niño territory in August.
The equatorial Pacific is in a neutral state, with atmospheric measures of ENSO divided between Niña and Niño-like patterns. WeatherTiger’s proprietary ENSO Whisperer is a little quicker to move the Pacific towards a weak El Niño, with the development of a weak or moderate +ENSO over the fall and winter of 2018 continues to be our preferred forecast solution.
A look ahead to the 2018 hurricane season reveals a below normal year in terms of total activity and U.S. landfall risk is the most likely outcome. Uncertainty remains elevated at this lead time due to lingering questions on how rapidly cooling Atlantic SSTs will evolve over the summer.
A favored pattern for the summer (May-July) period based on historical analogs and our proprietary modeling is a volatile pattern with a tendency for ridging over the Southern Plains. All else equal, this means a warmer and drier summer than average in the Plains and western corn belt, with more normal but still tilting warm conditions further east.
Observations and model data support at most a neutral-positive ENSO state through the summer. WeatherTiger’s proprietary ENSO Whisperer model has shifted cooler in the medium-range to reflect increased chances of continued neutral conditions as the North American planting and growing seasons approach.
A weak La Niña event continues in the equatorial Pacific, reduced in intensity since last month but still not having weakened back into ENSO neutral conditions. WeatherTiger’s March modeling continues to suggest that any transition to an El Nino will not be rapid, and neutral conditions are favored through much of the summer. This indicates that ENSO is less likely to be a major factor this U.S. growing season.
WeatherTiger’s January modeling is little changed from our previous several runs, continuing to suggest that La Niña peaks in January and begins to moderate in February, with neutral-negative conditions in March and April and true neutral conditions in May and June.
Winter 2017-18 is unlikely to be a historically cold winter on average, but there are signals that it is likely to be a somewhat active one nonetheless from a snow/ice perspective, particularly the further north and west you go.