1. 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 day or so, and then spread to the United States east coast by this weekend. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

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 day or so, and then spread to the United States east coast by this weekend. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 500 PM AST (2100 UTC), the center of Hurricane Sam was located near latitude 20.2 North, longitude 57.6 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 continue to pass well to the east northeast of the northern Leeward Islands through tonight. Maximum sustained winds are 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). An Air Force Reserve Unit Hurricane Hunter aircraft reported a minimum central pressure of 945 mb (27.91 inches).

Sam continues to exhibit a well-organized cloud pattern on satellite imagery, although there is some asymmetry of the coldest-topped convection around the center. The hurricane is also maintaining numerous banding features with well-defined upper-level anticyclonic outflow. Observations from an Air Force Hurricane Hunter plane showed peak 700 mb fight-level winds of 130 kt in the northeast quadrant which, using the standard reduction, corresponds to maximum surface winds of 117 kt. However, the maximum SFMR-observed surface winds were 103 kt. Based on these data, with more emphasis on the flight-level winds, the current intensity estimate is held at 115 kt. The aircraft also measured a minimum central pressure of 945 mb by dropsonde.

Since the hurricane is forecast to remain in an environment of low vertical shear and to remain over warm waters through 48 hours, Sam could restrengthen a little more during the next day or so. Since the Hurricane Hunters reported a concentric eyewall, short-term strengthening may be curtailed until the eyewall replacement cycle completes. Later in the forecast period, gradual weakening is likely due to cooler SSTs and increasing shear. The official intensity forecast is in very good agreement with the latest corrected consensus prediction. Sam will likely be close to extratropical transition around day 5.

The initial motion is still northwestward, or 310/8 kt. During the next few days, Sam is likely to move northwestward and then northward around the western periphery of a large subtropical high pressure system centered over the eastern Atlantic. A turn to the north-northeast and northeast is expected later in the forecast period as Sam begins to encounter the flow on the southern side of a large mid-tropospheric trough moving through Atlantic Canada. The track guidance models remain in excellent agreement through 72 hours, including the time that Sam passes by Bermuda. At days 4-5 there is some divergence of the model guidance, apparently due to how Sam may interact with the trough. Most notably the ECMWF is a lot slower than the other global models suggesting that the trough will at least partially bypass it in that case. Not much change has been made to the previous official forecast, however, and the NHC track remains very close to the TVCN dynamical model consensus.