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Tropical Storm Arthur Forecast Discussion Number 3
2020-05-17 10:48:37| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Sun May 17 2020 000 WTNT41 KNHC 170848 TCDAT1 Tropical Storm Arthur Discussion Number 3 NWS National Hurricane Center Miami FL AL012020 500 AM EDT Sun May 17 2020 Arthur has not changed much in organization overnight. The storm features a large curved convective band over the eastern semicircle of the circulation, and the low-level center appears to be exposed to the west of that band. The intensity is held at 35 kt in agreement with a subjective Dvorak estimate from TAFB and ADT estimates from UW-CIMSS. An Air Force Hurricane Hunter aircraft is scheduled to investigate the cyclone around 12Z which should provide a good estimate of Arthur's intensity. Although Arthur will be crossing back over the Gulf Stream tonight and Monday, vertical shear is forecast to steadily increase during that time. With these counteracting influences on intensity change, only slight strengthening is anticipated during the next 24-36 hours. The official forecast is close to the model consensus and is similar to the previous one. In 2-3 days, some strengthening due to baroclinic processes is possible, since the global models depict extratropical transition around that time. Later in the forecast period, the dynamical guidance shows weakening as the frontal gradients decrease. The storm has been moving a little to the left of the previous estimates and the motion is now around 015/8 kt. An approaching mid-level trough over the eastern U.S. should cause the cyclone to accelerate northeastward during the next 48 hours or so. Later in the forecast period, Arthur or its post-tropical remnants should turn eastward within a general westerly flow field. There has been a bit of a westward shift in much of the track guidance for the next 1-2 days, which has necessitated a leftward adjustment of the official forecast track. Since the new NHC forecast is now closer to the North Carolina Outer Banks, the Tropical Storm Watch has been changed to a Tropical Storm Warning for that area. Key Messages: 1. A Tropical Storm Warning is now in effect for a portion of the North Carolina coast. Tropical-storm-force winds and heavy rains are expected there on Monday. 2. Dangerous coastal surf conditions and rip currents are expected to spread northward from Florida to the mid-Atlantic states during the next few days. See products from your local National Weather Service Forecast Office for more details. FORECAST POSITIONS AND MAX WINDS INIT 17/0900Z 30.0N 77.6W 35 KT 40 MPH 12H 17/1800Z 31.2N 77.2W 40 KT 45 MPH 24H 18/0600Z 33.2N 76.4W 45 KT 50 MPH 36H 18/1800Z 35.5N 74.7W 45 KT 50 MPH 48H 19/0600Z 36.9N 72.0W 50 KT 60 MPH 60H 19/1800Z 37.3N 69.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 20/0600Z 37.0N 67.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 21/0600Z 36.0N 66.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 22/0600Z...DISSIPATED $$ Forecaster Pasch
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