Highlight: Subtropical system to develop off Southeast U.S. Coast this weekend.
|*TS Risk U.K.
Table 1: Current seasonal activity tropical cyclone forecasts for the North Atlantic basin. *Late May/early June updates ahead.
Seasonal forecast summary: Forecasters agree on the somewhat unique presence of conflicting signals for the upcoming North Atlantic tropical cyclone season. El Nino is likely and the attendant westerly shear in the upper atmosphere across the tropical North Atlantic makes for a difficult environment for tropical cyclone development. During an El Nino season, tropical cyclone activity is usually in the 8-10 storms, 2-4 hurricanes, and 1-2 intense hurricanes range. However, this season promises to bring a much warmer than normal North Atlantic basin including the subtropics and deep tropics. Above normal upper ocean heat favors higher than normal El Nino year activity and stronger storms. CSU, TSR U.K., and CIC will update their seasonal forecasts within the next 2 weeks. The NOAA forecast is near to higher than the CSU/TSR U.K./CIC consensus. As of now, the season is expected near normal but less busy than the active 2016-2022 period.
Today’s discussion: An area of low pressure just south of a frontal boundary off the Southeast U.S. Coast is producing thunderstorm activity east of Florida and into the Bahamas (Fig. 1) while a steady rain is evolving north of the frontal boundary on the Carolina Coast. Water temperatures are sufficiently warm for the area of low pressure to become a subtropical disturbance by tomorrow while drifting north-northeast and then possibly a subtropical depression turning into the upper coast of South Carolina Saturday night. Combined with the frontal system, this feature will cause gale force wind along the Southeast Coast this weekend and heavy rain piling to 2-6 in. near the SC/NC State Line and northwestward this weekend (Fig. 2). Once inland this system will steadily weaken.
Fig. 1: Satellite view of the North Atlantic basin.
Fig. 2: GFS rainfall amount forecast through Monday.