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Tropical Storm Arthur Forecast Discussion Number 8
2020-05-18 16:42:38| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Mon May 18 2020 000 WTNT41 KNHC 181442 TCDAT1 Tropical Storm Arthur Discussion Number 8 NWS National Hurricane Center Miami FL AL012020 1100 AM EDT Mon May 18 2020 Arthur has become a little better organized this morning with an overall increase in convection and banding noted since overnight. The first couple of reconnaissance aircraft passes through the center have shown that the pressure has fallen to around 996 mb. The plane has also reported several believable SFMR winds of 38-43 kt, and the anemometer on buoy 41025 at an elevation of only 4 m has reported a peak 1-minute wind of 37 kt. Based on these data the initial intensity is set at 45 kt. The forward speed of Arthur has continued to increase and the estimated motion is north-northeast at 14 kt. The cyclone should turn northeastward later today and begin moving away from the North Carolina Outer Banks as a mid-latitude trough approaches from the west. By Tuesday, Arthur is forecast to turn eastward within the mid-latitude westerlies. After that time, a deepening trough over the central and western Atlantic is expected to cause the cyclone to turn southeastward as the steering flow turns northwestward. The GFS and ECMWF are now in relatively good agreement on this scenario and the new NHC track forecast lies between those typically reliable models and the multi-model consensus aids. Although the vertical shear is increasing over the storm and it is soon moving over cooler waters, some strengthening due to baroclinic process is predicted over the next 24 hours. The storm should merge with a frontal boundary late tonight or early Tuesday which will complete Arthur's transition to an extratropical cyclone. By Wednesday, the post-tropical cyclone should begin to weaken as the frontal gradients decrease. The post-tropical cyclone should dissipate in about 96 h. Key Messages: 1. A Tropical Storm Warning is in effect for a portion of the North Carolina coast. Tropical-storm-force winds and heavy rains are expected there today. 2. Dangerous coastal surf conditions and rip currents are expected to spread northward along the southeast U.S. coast to the mid-Atlantic states during the next couple of days. See products from your local National Weather Service Forecast Office for more details. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 35.1N 75.2W 45 KT 50 MPH 12H 19/0000Z 36.4N 73.3W 50 KT 60 MPH 24H 19/1200Z 37.2N 70.1W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 20/0000Z 36.8N 67.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 20/1200Z 35.5N 65.8W 50 KT 60 MPH...POST-TROP/EXTRATROP 60H 21/0000Z 34.0N 65.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 21/1200Z 32.0N 64.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 22/1200Z...DISSIPATED $$ Forecaster Brown
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