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 PM AST (0300 UTC), the eye of Hurricane Sam was located near latitude 18.4 North, longitude 55.6 West. Sam is moving toward the northwest near 9 mph (15 km/h), and this general motion with an increase in forward speed is expected during the next couple of days. A turn toward the north is forecast by Friday. On the forecast track, Sam will pass well to the east and northeast of the northern Leeward Islands through Wednesday. Maximum sustained winds are near 140 mph (220 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 944 mb (27.88 inches).

Satellite images suggest that Sam has strengthened. The eyewall of the hurricane has become more intense, with a warmer eye noted during the past several hours since the last reconnaissance aircraft departed. The initial wind speed is nudged upward to 120 kt, a little above what the previous aircraft mission from this afternoon supported. Another Air Force Reserve Hurricane Hunter plane is scheduled to fly through Sam in a few hours for a better look at the intensity.

Sam is forecast to move into an area with somewhat lower wind shear and higher ocean heat content by late Wednesday. In addition, the hurricane will likely be moving a little faster, which decreases the upwelling potential under the storm. These factors lead me to believe Sam isn't quite done intensifying, and could reach another peak sometime late Wednesday or Thursday. The one fly-in-the- ointment to this forecast is another eyewall replacement cycle potentially beginning, although recent microwave data doesn't give that impression. Thus, the new forecast is raised from the last one during the first couple of days, on the higher side of the guidance. A more consistent weakening trend is expected late week, due to cooler SSTs and increasing shear, and no significant changes were made to the official forecast at long range.

The hurricane continues moving northwestward at about 8 kt. Models are locked into this track continuing for the next day or two at a faster pace around the southwestern portion of a strengthening Atlantic subtropical ridge. Thereafter, Sam should turn northward on Friday and northeastward this weekend, likely a fair distance east of Bermuda, due to a large mid-latitude trough moving off of the United States east coast. Model guidance remains in close agreement on almost all of the forecast, and the only significant change from the last advisory is an eastward adjustment on Day 5 due to guidance suggesting that Sam gets shunted more eastward by the trough, rather than captured by it.