1. Large swells generated by Sam are affecting the Leeward Islands and will spread to portions of the Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda by Thursday or Friday. Significant swells will likely reach the east coast of the United States and Atlantic Canada by the weekend. These swells will likely cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the advice of lifeguards and local officials through the upcoming weekend.

There are no coastal watches or warnings in effect.

Key messages for Sam can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles during the next several days. Swells are expected to reach Bermuda and the Bahamas in a couple of days, and then spread to the United States east coast late this week. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 1100 AM AST (1500 UTC), the eye of Hurricane Sam was located near latitude 17.5 North, longitude 54.3 West. Sam is moving toward the northwest near 8 mph (13 km/h) and this motion with an increase in forward is expected during the next couple of days. A turn toward the north is forecast to occur by Friday. On the forecast track, Sam will pass well to the east of the northern Leeward Islands through Wednesday. Maximum sustained winds remain near 130 mph (215 km/h) with higher gusts. Sam is a category 4 hurricane on the Saffir Simpson Hurricane Wind Scale. Some fluctuations in intensity are expected during the next couple of days, but Sam is forecast to remain a major hurricane through late this week. Hurricane force winds extend outward up to 40 miles (65 km) from the center and tropical storm force winds extend outward up to 140 miles (220 km). The estimated minimum central pressure is 952 mb (28.12 inches).

Satellite images indicate that Sam has been generally steady in strength during the past several hours, and it remains a powerful category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. The storm has a well-defined eye, and the convective pattern surrounding the center is fairly symmetric. A 1043 UTC SSMIS pass showed a closed and symmetric eyewall, with no indication of a concentric eyewall. The latest Dvorak classifications from TAFB and SAB were 5.5/102 kt and the CIMSS automated technique is currently 6.2/120 kt. Based on these satellite estimates and the overnight reconnaissance data, the initial intensity is held at 115 kt. Another Air Force Hurricane Hunter aircraft is scheduled to investigate Sam this afternoon.

The major hurricane is moving slowly northwestward, with the initial motion estimated to be 305/7 kt. A mid-level ridge situated to the north-northeast of Sam is expected to shift eastward as a deep-layer trough digs southeastward over the western Atlantic. This change in the large-scale pattern should cause Sam to speed up and gradually turn toward the north in 2 or 3 days and then to the northeast in 4 to 5 days. The models are in fairly good agreement, and the new forecast track is essentially an update of the previous one. Based on the forecast, Sam should pass well east of the northern Leeward Island through Wednesday and east of Bermuda Friday night and Saturday.

Sam is expected to remain in favorable environmental conditions for it to maintain its intensity, or perhaps strengthen slightly, during the next day or two. However, after that time, a gradual increase in southerly shear should promote a slow weakening trend, and Sam will likely be beginning its transition to an extratropical cyclone toward the end of the forecast period. The NHC intensity forecast is also an update of the previous one and in line with the various consensus aids. Sam is expected to remain a major hurricane during the next several days.

The initial wind radii have been adjusted based on a 1114 UTC ASCAT-A pass.