FLORIDA
STORMS
Hurricane Sam
LOCATED
850 MI ESE OF THE NORTHERN LEEWARD ISLANDS
WINDS
145 MPH
PRESSURE
943 MB
MOVING
NW AT 7 MPH
From the National Hurricane Center at 1100 PM AST Sun Sep 26 2021
Hurricane hunter aircraft finds Sam has peaked in intensity.
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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 1100 PM AST (0300 UTC), the center of Hurricane Sam was located by a NOAA Hurricane Hunter aircraft near latitude 14.7 North, longitude 50.8 West. Sam is moving toward the northwest near 7 mph (11 km/h), and this motion is expected to continue for the next few days, along with a gradual increase in forward speed beginning around midweek. Data from the reconnaissance aircraft indicate that 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, slow weakening is forecast. However, Sam is still expected to remain a major hurricane through midweek. Sam remains a small tropical cyclone. 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 based on recent reports from the aircraft is 943 mb (27.85 inches).

At 1100 PM AST (0300 UTC), the center of Hurricane Sam was located by a NOAA Hurricane Hunter aircraft near latitude 14.7 North, longitude 50.8 West. Sam is moving toward the northwest near 7 mph (11 km/h), and this motion is expected to continue for the next few days, along with a gradual increase in forward speed beginning around midweek. Data from the reconnaissance aircraft indicate that 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, slow weakening is forecast. However, Sam is still expected to remain a major hurricane through midweek. Sam remains a small tropical cyclone. 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 based on recent reports from the aircraft is 943 mb (27.85 inches).

A NOAA Hurricane Hunter aircraft investigating Sam this afternoon and evening found that the major hurricane likely peaked in intensity at around 135 kt with a central pressure of about 929 mb between 1900-2200 UTC when the eye contracted down to about 7 nmi in diameter. Since that time, however, wind and radar data from the aircraft reveal that Sam has been undergoing an eyewall replacement cycle (ERC), including significant erosion of the eyewall convection in the eastern semicircle, which has resulted in the central pressure increasing by at least 14 mb in only a few hours. The eye diameter has also doubled in size now. The ERC is also confirmed by the ragged inner-core convection and cloud-filled eye that have developed in satellite imagery. The advisory intensity of 125 kt is based on a blend of the available reliable SFMR surface wind data and flight-level wind data, and also using the pressure-wind relationship for a 943-mb central pressure.

The initial motion estimate is now 315/06 kt. A strong subtropical ridge to the north and northeast of Sam is forecast by the global and regional models to remain entrenched across the central and eastern Atlantic for the next several days, resulting in the hurricane moving northwestward for the 72 hours. Thereafter, a mid- to upper-level trough is forecast to dig southward just off the U.S. east coast, creating a deep southerly flow regime that will act to accelerate Sam northward on days 4 and 5. The new NHC track forecast is similar the previous advisory, and lies close to the tightly packed consensus models through 72 hours. In the 96-120 hour period, the models diverge significantly on when and where Sam will begin moving out toward the north, and the NHC track forecast favors the more eastward GFS solution since that model has been performing quite well with Sam thus far.

Now that Sam is undergoing an ERC, fluctuations in intensity could occur for the next day or two while the vertical wind shear remains low at least than 10 kt. Thereafter, a slow weakening trend is expected due to a modest increase in the wind shear from the southwest and occasional intrusions of drier mid-level air. The NHC intensity forecast is a little lower than the previous advisory, mainly due to the lower initial intensity, and closely follows the HCCA and IVCN consensus model intensity forecasts.

A NOAA Hurricane Hunter aircraft investigating Sam this afternoon and evening found that the major hurricane likely peaked in intensity at around 135 kt with a central pressure of about 929 mb between 1900-2200 UTC when the eye contracted down to about 7 nmi in diameter. Since that time, however, wind and radar data from the aircraft reveal that Sam has been undergoing an eyewall replacement cycle (ERC), including significant erosion of the eyewall convection in the eastern semicircle, which has resulted in the central pressure increasing by at least 14 mb in only a few hours. The eye diameter has also doubled in size now. The ERC is also confirmed by the ragged inner-core convection and cloud-filled eye that have developed in satellite imagery. The advisory intensity of 125 kt is based on a blend of the available reliable SFMR surface wind data and flight-level wind data, and also using the pressure-wind relationship for a 943-mb central pressure.

The initial motion estimate is now 315/06 kt. A strong subtropical ridge to the north and northeast of Sam is forecast by the global and regional models to remain entrenched across the central and eastern Atlantic for the next several days, resulting in the hurricane moving northwestward for the 72 hours. Thereafter, a mid- to upper-level trough is forecast to dig southward just off the U.S. east coast, creating a deep southerly flow regime that will act to accelerate Sam northward on days 4 and 5. The new NHC track forecast is similar the previous advisory, and lies close to the tightly packed consensus models through 72 hours. In the 96-120 hour period, the models diverge significantly on when and where Sam will begin moving out toward the north, and the NHC track forecast favors the more eastward GFS solution since that model has been performing quite well with Sam thus far.

Now that Sam is undergoing an ERC, fluctuations in intensity could occur for the next day or two while the vertical wind shear remains low at least than 10 kt. Thereafter, a slow weakening trend is expected due to a modest increase in the wind shear from the southwest and occasional intrusions of drier mid-level air. The NHC intensity forecast is a little lower than the previous advisory, mainly due to the lower initial intensity, and closely follows the HCCA and IVCN consensus model intensity forecasts.

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