The Hurricane Genesis & Outlook (HUGO) Project at Coastal Carolina University anticipates a “slightly below normal” hurricane season in 2017, according to its extended range forecast for the North Atlantic released at the end of June.
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Scenarios for the 2017 hurricane season are dependent on a number of factors, according to Len Pietrafesa, research professor in CCU’s Burroughs & Chapin Center for Marine and Wetland Studies (BCCMWS) and leader of the HUGO team.
“A main climate factor, the El Nino Southern Oscillation (ENSO), is between cold (La Nina) and warm (El Nino) phases in the equatorial Pacific Ocean and has confused the issue to date as shown by a recent National Oceanic & Atmospheric Administration forecast of ‘above normal’ and a Colorado State University forecast of ‘below normal,’ ” says Pietrafesa.
Based on climate factors available in early June, the HUGO outlook (detailed in the table below) predicts that there will be a range of 8 to 14 named tropical storms (with 11 most likely and 12 being the long-term average), with from 3 to 8 (with 5 most likely and 6 being the long-term average) becoming hurricanes and 1 to 3 (with 2 most likely and 3 being the long-term average) becoming major hurricanes during the 2017 season (June 1 to Nov. 30).
For both the U.S. East Coast and the U.S. Gulf Coast, the HUGO study predicts a landfall probability range of zero to 2 for both coastlines. The most probable scenario calls for at least 1 hurricane landfall on the East Coast and at least 1 hurricane landfall on the Gulf Coast during the 2017 season. The second most likely scenario is that no hurricanes will make landfall on either coast. The third most likely possibility is that 2 hurricanes will make landfall on the U.S. Atlantic East Coast and for 2 hurricanes to make landfall on the U.S. Gulf Coast.
key issues at this point in time are (1) how the El Nino will be developing in the Equatorial Pacific Ocean and (2) how warm the upper ocean of the North Atlantic Ocean will become,” says Pietrafesa.
The above scenario is highly dependent on the variations of climate factors in June and July, primarily ENSO and the Atlantic Multi-decadal Oscillation (AMO), which is the ocean surface temperature of the North Atlantic Ocean. An updated outlook will be released in late July as more observational climate data become available.
Past HUGO outlook forecasts have proved to be highly accurate. The 2016 and 2015 outlooks were correct in nearly every category (number of tropical storms, number of major hurricanes, landfalls on both the East Coast and Gulf Coast). The 2015 outlook correctly forecast a most likely scenario that no hurricanes would make landfall on either the East or Gulf coasts and also accurately forecast the number of hurricanes at 4. The 2016 forecasts for all numbers were spot on, including 1 landfall on the Gulf Coast (Hermine) and 1 on the East Coast (Matthew).