The 2019 Atlantic Hurricane Season is expected to deliver very slightly below long-term average levels of tropical storm activity, according to industry supported researcher Tropical Storm Risk (TSR).
TSR, the insurance and reinsurance industry supported tropical weather researchers from London, had already given an early forecast of long-range activity levels for the 2019 Atlantic hurricane season in which they opted for 8 to 16 tropical storms, 2 to 8 of which would become hurricanes and 0 to 4 intense hurricanes of Category 3 strength or greater.
Now, the TSR team has published their April forecast update, in which they maintain their forecast for 12 tropical storms, 5 hurricanes and 2 major hurricanes, so the mid-point of the previous extended range forecast figures.
“Based on current and projected climate signals, Atlantic basin tropical cyclone activity is forecast to be about 20% below the 1950-2018 long-term norm and about 30% below the recent 2009-2018 10-year norm,” the researchers explained.
Continuing, “TSR’s main predictor is the forecast July-September trade wind speed over the Caribbean Sea and tropical North Atlantic. This parameter influences cyclonic vorticity (the spinning up of storms) and vertical wind shear in the main hurricane track region. At present TSR anticipates that the July-September trade wind speed in 2019 will be slightly stronger than normal – due mainly to a continuance of weak-to-moderate El Niño conditions – and that this will have a suppressing effect on North Atlantic hurricane activity in 2019.”
El Nino has featured in every forecast seen to-date, with meteorologists now expecting that at least a weak El Nino will persist well into the hurricane season, perhaps into the most active period of the year.
However, TSR’s forecasters note that forecast uncertainties remain large for the 2019 hurricane season, in particular the forecasts for the El Niño Southern Oscillation and the North Atlantic Oscillation, key climate factors that influence levels of tropical storm activity.
TSR’s forecasters give a 43% chance that the 2019 hurricane seasons accumulated cyclone energy (ACE) will be below normal, which is telling as its own forecast for the number of storms and hurricanes points to an ACE of around 81.
TSR also forecasts that as many as 2 tropical storms will make landfall in the United States this season, as well as 1 hurricane.
However, the team note the lack of skill in these forecasts and it’s also important to stress that this is a prediction based on the amount of ACE U.S. landfalling storms may generate.
Overall, it is the anticipated suppression of July to September trade winds in the Atlantic, due to El Nino, that causes the below average forecast but also creates high levels of uncertainty, as forecasting the duration of the suppressing effect is extremely difficult.
TSR’s forecast of 2019 Atlantic hurricane activity joins others that all point to around normal to slightly below levels of storm formation during the season ahead.
Our Artemis average forecast for the 2019 Atlantic hurricane season remains for 13 named storms, 5 hurricanes and 2 major hurricanes, across the forecasting teams we track.
Keep track of the season as it develops over on our dedicated 2019 Atlantic Hurricane Season page.
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