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Post-Tropical Cyclone Helene Forecast Discussion Number 18
2024-09-27 22:35:58| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Fri Sep 27 2024 367 WTNT44 KNHC 272035 TCDAT4 Post-Tropical Cyclone Helene Discussion Number 18 NWS National Hurricane Center Miami FL AL092024 400 PM CDT Fri Sep 27 2024 Helene has been producing catastrophic flooding over portions of the southeast U.S. and southern Appalachians, and the associated heavy rains are shifting westward into the Ohio and Tennessee Valleys. Satellite images and surface observations indicate that Helene has completed extratropical transition, and the initial intensity is set at 30 kt. The cyclone is moving to the north-northwest at 15 kt. A slowdown is expected tonight, and the cyclone is forecast to stall over the Tennessee Valley this weekend, likely resulting in continued and prolonged rainfall. This is the last tropical cyclone discussion issued by the National Hurricane Center on Helene. Future information on this system can be found in discussions issued by the Weather Prediction Center beginning at 1000 PM CDT, under AWIPS header TCDAT4, WMO header WTNT44 KWNH, and on the web at www.hurricanes.gov. Rainfall forecasts for the United States can always be found at https://www.wpc.ncep.noaa.gov/qpf/qpf2.shtml and outlooks of flash flood risks can be found at https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php . KEY MESSAGES: 1. Historic, catastrophic and life-threatening flash and urban flooding, including numerous major landslides, will continue across portions of the southern Appalachians through this evening, followed by gradual improvement tonight and into Saturday. Widespread serious river flooding is ongoing, some of which will be major to record breaking. 2. There is a possibility of long-duration power outages in portions of the southeast U.S. If you use a generator, be sure it is placed outside at least 20 feet away from doors, windows, and garages to avoid deadly carbon monoxide poisoning. 3. Use caution after the system passes as deadly hazards remain including downed power lines and flooded areas. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 37.5N 85.5W 30 KT 35 MPH...POST-TROPICAL 12H 28/0600Z 37.9N 87.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 24H 28/1800Z 37.7N 87.2W 20 KT 25 MPH...POST-TROP/EXTRATROP 36H 29/0600Z 37.5N 87.3W 20 KT 25 MPH...POST-TROP/EXTRATROP 48H 29/1800Z 37.3N 87.0W 20 KT 25 MPH...POST-TROP/EXTRATROP 60H 30/0600Z...DISSIPATED $$ Forecaster Cangialosi
Category:Transportation and Logistics
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Post-Tropical Cyclone Helene Wind Speed Probabilities Number 18
2024-09-27 22:35:32| National Hurricane Center (Atlantic)
Issued at 2100 UTC FRI SEP 27 2024 000 FONT14 KNHC 272035 PWSAT4 POST-TROPICAL CYCLONE HELENE WIND SPEED PROBABILITIES NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092024 2100 UTC FRI SEP 27 2024 AT 2100Z THE CENTER OF POST-TROPICAL CYCLONE HELENE WAS LOCATED NEAR LATITUDE 37.5 NORTH...LONGITUDE 85.5 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 30 KTS...35 MPH...55 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 18Z FRI 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 18Z FRI 06Z SAT 18Z SAT 06Z SUN 18Z SUN 18Z MON 18Z TUE PERIODS TO TO TO TO TO TO TO 06Z SAT 18Z SAT 06Z SUN 18Z SUN 18Z MON 18Z TUE 18Z WED FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT $$ FORECASTER CANGIALOSI
Category: Transportation and Logistics
Summary for Tropical Storm Joyce (AT1/AL112024)
2024-09-27 22:35:28| National Hurricane Center (Atlantic)
...JOYCE BECOMES BETTER ORGANIZED AND STRENGTHENS... As of 5:00 PM AST Fri Sep 27 the center of Joyce was located near 18.6, -44.0 with movement NW at 13 mph. The minimum central pressure was 1001 mb with maximum sustained winds of about 50 mph.
Category: Transportation and Logistics