Hurricane Sam
LOCATED
940 MI ESE OF THE NORTHERN LEEWARD ISLANDS
WINDS
145 MPH
PRESSURE
943 MB
MOVING
WNW AT 8 MPH
From the National Hurricane Center at 500 AM AST Sun Sep 26 2021
Sam remains a category four hurricane.
TAP LINKS BELOW TO FOCUS
Alerts
hazards
summary
DISCUSSION

There are no coastal watches or warnings in effect.

There are no coastal watches or warnings in effect.

SURF: Swells generated by Sam are forecast to reach the Lesser Antilles early this week. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

SURF: Swells generated by Sam are forecast to reach the Lesser Antilles early this week. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 500 AM AST (0900 UTC), the center of Hurricane Sam was located near latitude 13.8 North, longitude 49.7 West. Sam is moving toward the west northwest near 8 mph (13 km/h). This general motion is expected to continue today, followed by a turn toward the northwest on Monday. Then, a northwestward motion is forecast to continue through midweek. Maximum sustained winds are near 145 mph (230 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 day or so. Thereafter, some slow weakening is forecast. Sam is a small hurricane. Hurricane force winds extend outward up to 30 miles (45 km) from the center and tropical storm force winds extend outward up to 90 miles (150 km). The estimated minimum central pressure is 943 mb (27.85 inches).

At 500 AM AST (0900 UTC), the center of Hurricane Sam was located near latitude 13.8 North, longitude 49.7 West. Sam is moving toward the west northwest near 8 mph (13 km/h). This general motion is expected to continue today, followed by a turn toward the northwest on Monday. Then, a northwestward motion is forecast to continue through midweek. Maximum sustained winds are near 145 mph (230 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 day or so. Thereafter, some slow weakening is forecast. Sam is a small hurricane. Hurricane force winds extend outward up to 30 miles (45 km) from the center and tropical storm force winds extend outward up to 90 miles (150 km). The estimated minimum central pressure is 943 mb (27.85 inches).

Sam remains a small but intense hurricane this morning, with a well-defined 10 n mi-wide eye. A 0500 UTC AMSR-2 microwave pass reveals Sam has a compact inner core of deep convection surrounding its eye, with curved convective bands primarily extending around the northern and eastern portions of the circulation. Infrared cloud top temperatures briefly warmed overnight in portions of Sam's central dense overcast, perhaps due to some intrusions of drier mid-level air. The 06z objective and subjective satellite estimates ranged from 113-127 kt, but Sam's satellite presentation has improved in recent infrared imagery as cloud top temperatures are cooling around the eye. Thus, the initial intensity is held at 125 kt for this advisory. NOAA aircraft are scheduled to investigate Sam later this afternoon, which should provide helpful information about the structure and intensity of the hurricane.

Sam is moving toward the west-northwest, or 295/7 kt. A deep-layer subtropical ridge to the north and northeast of Sam should generally steer the hurricane west-northwestward to northwestward for the next several days. By midweek, an amplifying upper-level trough will move off the east coast of the U.S. and dig southward over the western Atlantic, which will erode the western extent of the steering ridge. The deep-layer southerly flow ahead of the trough should cause Sam to begin recurving, with a somewhat faster north-northwestward motion forecast by day 5. The latest NHC track forecast is very similar to the previous one and generally lies between the HFIP corrected consensus approach (HCCA) and TVCA aids. At days 4-5, there is more spread in the track guidance, with the ECMWF on the far left side of the guidance envelope and the GFS on the far right. The NHC forecast track has been nudged just slightly to the left at 96 and 120 h, but it still lies to the right of HCCA.

The hurricane will likely experience some fluctuations in intensity during the next day or two. On the one hand, Sam remains over warm sea-surface temperatures of around 28.5 deg C, with vertical wind shear less than 10 kt as diagnosed from the SHIPS guidance. However, GOES-16 water vapor imagery shows some drier mid-level air in the surrounding environment that may periodically entrain into the inner core of Sam. Additionally, the onset of an eyewall replacement cycle remains a distinct possibility at this stage of Sam's life cycle, although the latest microwave data does not suggest one is imminent. The official NHC intensity forecast lies on the high end of the guidance for the first 36-48 h of the forecast period. Thereafter, the NHC forecast trends closer to the HCCA and IVCN consensus aids. Some gradual weakening is forecast later in the period as the southwesterly vertical wind shear begins to increase, but Sam is still forecast to remain a major hurricane through the 5-day period.

Sam remains a small but intense hurricane this morning, with a well-defined 10 n mi-wide eye. A 0500 UTC AMSR-2 microwave pass reveals Sam has a compact inner core of deep convection surrounding its eye, with curved convective bands primarily extending around the northern and eastern portions of the circulation. Infrared cloud top temperatures briefly warmed overnight in portions of Sam's central dense overcast, perhaps due to some intrusions of drier mid-level air. The 06z objective and subjective satellite estimates ranged from 113-127 kt, but Sam's satellite presentation has improved in recent infrared imagery as cloud top temperatures are cooling around the eye. Thus, the initial intensity is held at 125 kt for this advisory. NOAA aircraft are scheduled to investigate Sam later this afternoon, which should provide helpful information about the structure and intensity of the hurricane.

Sam is moving toward the west-northwest, or 295/7 kt. A deep-layer subtropical ridge to the north and northeast of Sam should generally steer the hurricane west-northwestward to northwestward for the next several days. By midweek, an amplifying upper-level trough will move off the east coast of the U.S. and dig southward over the western Atlantic, which will erode the western extent of the steering ridge. The deep-layer southerly flow ahead of the trough should cause Sam to begin recurving, with a somewhat faster north-northwestward motion forecast by day 5. The latest NHC track forecast is very similar to the previous one and generally lies between the HFIP corrected consensus approach (HCCA) and TVCA aids. At days 4-5, there is more spread in the track guidance, with the ECMWF on the far left side of the guidance envelope and the GFS on the far right. The NHC forecast track has been nudged just slightly to the left at 96 and 120 h, but it still lies to the right of HCCA.

The hurricane will likely experience some fluctuations in intensity during the next day or two. On the one hand, Sam remains over warm sea-surface temperatures of around 28.5 deg C, with vertical wind shear less than 10 kt as diagnosed from the SHIPS guidance. However, GOES-16 water vapor imagery shows some drier mid-level air in the surrounding environment that may periodically entrain into the inner core of Sam. Additionally, the onset of an eyewall replacement cycle remains a distinct possibility at this stage of Sam's life cycle, although the latest microwave data does not suggest one is imminent. The official NHC intensity forecast lies on the high end of the guidance for the first 36-48 h of the forecast period. Thereafter, the NHC forecast trends closer to the HCCA and IVCN consensus aids. Some gradual weakening is forecast later in the period as the southwesterly vertical wind shear begins to increase, but Sam is still forecast to remain a major hurricane through the 5-day period.

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