ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Tropical Storm Arthur Discussion Number 10 NWS National Hurricane Center Miami FL AL012020 1100 PM EDT Mon May 18 2020 Arthur's cloud shield has shifted to the left or north side of the cyclone's direction of motion since the previous advisory, which is a distinctive sign of a tropical cyclone beginning to lose its tropical characteristics, especially now due to the cyclone moving over 23 deg C sea-surface temperatures. However, there remains enough convection within 45-75 nmi of the center for Arthur to still be classified as a tropical cyclone. The initial intensity has been increased to 50 kt based on a recent 0129 UTC ASCAT-B overpass that indicated several 50-51 kt wind vectors existed in the northwestern quadrant. The initial motion estimate is 070/13 kt. Arthur should move east- northeastward tonight and then turn toward the east by Tuesday morning as the cyclone moves around the northern periphery of a low- to mid-level ridge. On day 2, all of the global models are forecasting the mid- and upper-level circulations to separate from the low-level circulation, with the latter feature dropping southeastward and then southward around the eastern portion of a low-level ridge. The new track forecast is similar to but slightly east of the previous advisory track on days 2 and 3, and closely follows a blend of the consensus models TVCN and GFEX. Only slight strengthening is expected during the next day or so due to baroclinic effects while Arthur undergoes extratropical transition. Data from NOAA Buoy 44014, located west Arthur's center, indicate that a cold front passed over that station around 2300 UTC, which would place the front about 50-75 nmi west of the cyclone at this time. Therefore, a merger with the front is likely during the next 12 hours. The system should begin to steadily weaken shortly after 24 hours when Arthur will be moving over SSTs near 20 deg C, and in conjunction with the aforementioned decoupling of the circulations. Dangerous coastal surf conditions and rip currents are expected to continue along portions of the mid-Atlantic and southeast U.S. coasts 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 19/0300Z 36.4N 72.4W 50 KT 60 MPH 12H 19/1200Z 36.9N 70.1W 55 KT 65 MPH...POST-TROP/EXTRATROP 24H 20/0000Z 36.4N 67.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 20/1200Z 35.2N 65.8W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 21/0000Z 33.7N 64.6W 40 KT 45 MPH...POST-TROP/EXTRATROP 60H 21/1200Z 32.3N 64.4W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 22/0000Z 30.9N 64.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 23/0000Z...DISSIPATED $$ Forecaster Stewart NNNN