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Hurricane Sam Graphics
2021-09-29 10:40:34| National Hurricane Center (Atlantic)
5-Day Uncertainty Track last updated Wed, 29 Sep 2021 08:40:34 GMT Wind Speed Probabilities last updated Wed, 29 Sep 2021 09:22:48 GMT
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Hurricane Sam Forecast Discussion Number 27
2021-09-29 10:38:37| National Hurricane Center (Atlantic)
Issued at 500 AM AST Wed Sep 29 2021 000 WTNT43 KNHC 290838 TCDAT3 Hurricane Sam Discussion Number 27 NWS National Hurricane Center Miami FL AL182021 500 AM AST Wed Sep 29 2021 The eye of Sam has become cloud filled in infrared satellite imagery overnight, but the ring of deep convection surrounding the eye has cooled. There appears to be a southwest-to-northeast tilt to Sam's circulation as some modest southwesterly shear seems to be impinging on the hurricane. An Air Force Reserve Hurricane Hunter aircraft that has been investigating Sam overnight shows that the hurricane continues to fluctuate in intensity. The aircraft has reported a peak flight-level wind of 124 kt and SFMR winds of 108 kt. Therefore the initial wind speed has been set at 115 kt, which leans toward the higher flight-level-to-surface wind reduction. The aircraft also reported a minimum pressure of 950 mb, which is up a few millibars from the flight yesterday afternoon. The fluctuations in intensity that Sam has experienced over the past couple of days are fairly typical for hurricanes of this strength. As mentioned in the previous advisory, Sam will be moving into a lower vertical wind shear environment, and the expected faster forward speed decreases the potential for upwelling beneath the storm. As a result, some re-intensification is forecast, but difficult-to-predict eyewall replacement cycles could cause additional fluctuations in intensity over the next day or two. After 60 to 72 hours, a more pronounced weakening trend is likely to begin as the storm moves over cooler SSTs and the vertical shear increases. The global models indicate that Sam will begin its transition into a powerful extratropical cyclone late in the period, but that transition will likely not be completed until after 120 h. Sam is moving northwestward at about 8 kt. The track guidance remains in excellent agreement through 96 hours as Sam should move northwestward and then northward around the western portion of the subtropical ridge over the eastern Atlantic during the next few days. By Saturday, Sam is forecast to turn northeastward between the aforementioned ridge and a deep-layer trough over the northeastern U.S. and Nova Scotia. By late in the period, there is an increase in spread in the guidance which is related to how Sam interacts with the deep-layer trough. For now, the NHC track forecast at days 4 and 5 lies between the TVCA multi-model consensus and the HFIP corrected consensus aid. Overall, little change to the previous NHC track forecast was required for this advisory. Key Messages: 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. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 18.9N 56.2W 115 KT 130 MPH 12H 29/1800Z 19.7N 57.3W 120 KT 140 MPH 24H 30/0600Z 21.0N 58.9W 120 KT 140 MPH 36H 30/1800Z 22.8N 60.4W 120 KT 140 MPH 48H 01/0600Z 25.2N 61.5W 115 KT 130 MPH 60H 01/1800Z 27.9N 62.0W 115 KT 130 MPH 72H 02/0600Z 30.8N 61.5W 110 KT 125 MPH 96H 03/0600Z 35.8N 57.5W 95 KT 110 MPH 120H 04/0600Z 40.8N 52.0W 80 KT 90 MPH $$ Forecaster Brown
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Summary for Hurricane Sam (AT3/AL182021)
2021-09-29 10:37:12| National Hurricane Center (Atlantic)
...AIR FORCE HURRICANE HUNTERS FIND SAM FLUCTUATING IN STRENGTH... As of 5:00 AM AST Wed Sep 29 the center of Sam was located near 18.9, -56.2 with movement NW at 9 mph. The minimum central pressure was 950 mb with maximum sustained winds of about 130 mph.
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Hurricane Sam Public Advisory Number 27
2021-09-29 10:37:12| National Hurricane Center (Atlantic)
Issued at 500 AM AST Wed Sep 29 2021 000 WTNT33 KNHC 290837 TCPAT3 BULLETIN Hurricane Sam Advisory Number 27 NWS National Hurricane Center Miami FL AL182021 500 AM AST Wed Sep 29 2021 ...AIR FORCE HURRICANE HUNTERS FIND SAM FLUCTUATING IN STRENGTH... SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...18.9N 56.2W ABOUT 455 MI...730 KM E OF THE NORTHERN LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H PRESENT MOVEMENT...NW OR 310 DEGREES AT 9 MPH...15 KM/H MINIMUM CENTRAL PRESSURE...950 MB...28.06 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 500 AM AST (0900 UTC), the center of Hurricane Sam was located near latitude 18.9 North, longitude 56.2 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 tonight. Data from an Air Force Reserve Hurricane Hunter aircraft indicate that the 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 125 miles (205 km). The latest minimum central pressure estimated from reconnaissance aircraft data is 950 mb (28.06 inches). HAZARDS AFFECTING LAND ---------------------- 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 two, 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. NEXT ADVISORY ------------- Next complete advisory at 1100 AM AST. $$ Forecaster Brown
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Hurricane Sam Wind Speed Probabilities Number 27
2021-09-29 10:37:12| National Hurricane Center (Atlantic)
Issued at 0900 UTC WED SEP 29 2021 000 FONT13 KNHC 290837 PWSAT3 HURRICANE SAM WIND SPEED PROBABILITIES NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182021 0900 UTC WED SEP 29 2021 AT 0900Z THE CENTER OF HURRICANE SAM WAS LOCATED NEAR LATITUDE 18.9 NORTH...LONGITUDE 56.2 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 115 KTS...130 MPH...215 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) ATLANTIC STANDARD TIME (AST)...SUBTRACT 4 HOURS FROM Z TIME EASTERN DAYLIGHT TIME (EDT)...SUBTRACT 4 HOURS FROM Z TIME CENTRAL DAYLIGHT TIME (CDT)...SUBTRACT 5 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 06Z WED AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 06Z WED 18Z WED 06Z THU 18Z THU 06Z FRI 06Z SAT 06Z SUN PERIODS TO TO TO TO TO TO TO 18Z WED 06Z THU 18Z THU 06Z FRI 06Z SAT 06Z SUN 06Z MON FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT HIBERNIA OILFD 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) CAPE RACE NFLD 34 X X( X) X( X) X( X) X( X) X( X) 7( 7) ILE ST PIERRE 34 X X( X) X( X) X( X) X( X) X( X) 4( 4) SABLE ISLAND 34 X X( X) X( X) X( X) X( X) X( X) 3( 3) BERMUDA 34 X X( X) X( X) X( X) 20(20) 9(29) X(29) BERMUDA 50 X X( X) X( X) X( X) 5( 5) 3( 8) X( 8) BERMUDA 64 X X( X) X( X) X( X) 1( 1) 2( 3) X( 3) BARBUDA 34 1 2( 3) 1( 4) X( 4) X( 4) X( 4) X( 4) $$ FORECASTER BROWN
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