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#900112 (Received by flhurricane at: 4:53 PM 27.Aug.2017) TCDAT5 Potential Tropical Cyclone Ten Discussion Number 1 NWS National Hurricane Center Miami FL AL102017 500 PM EDT Sun Aug 27 2017 Convection associated with the broad area of low pressure located east of the Georgia coast has increased markedly today. Visibile satellite imagery shows multiple low-level swirls rotating around a mean center, but ASCAT data earlier today showed that the circulation was not yet well-defined. The ASCAT data and buoy observations indicate that the initial intensity is 30 kt, and buoy data suggest the central pressure is around 1007 mb. While the system is expected to remain sheared, it has a high chance of becoming a tropical depression or tropical storm before it becomes baroclinic in about 48 hours. Given that, and the potential for this system to bring tropical storm conditions to the coast from northern South Carolina through North Carolina, advisories are being initiated on this system as a Potential Tropical Cyclone. The system is currently moving little in a region of weak steering, but should begin to move slowly northward and then quickly accelerate northeastward ahead of a mid-latitude trough moving into the mid-Atlantic states. The NHC forecast follows the trend of the global models keeping the low center near the coast, but as usual there is more uncertainty than usual in the track forecast for a weak/developing system. After the system moves into the western Atlantic, it should continue accelerating east-northeastward ahead of the upper trough through the end of the period. Despite the sheared envirionment, the system should be able to intensify a little via diabatic processes before it intensifies further as it undergoes a more substantial baroclinic intensification at 48 hours and beyond. The NHC intensity forecast follows the intensity consensus through 36 hours and then follows the trend of the global model guidance and guidance from the NOAA Ocean Prediction Center. Although the potential impacts are within 36 hours, given the uncertainty in whether tropical storm force winds will occur on land in northeastern South Caroilna and southeastern North Carolina, south, a tropical storm watch has been issued for these areas. Note that north of Duck, North Carolina, hazards from this system will be handled with non-tropical products issued by local National Weather Service offices. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 31.2N 80.0W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 28/0600Z 31.6N 80.1W 35 KT 40 MPH...TROPICAL CYCLONE 24H 28/1800Z 32.4N 80.0W 35 KT 40 MPH 36H 29/0600Z 34.1N 78.0W 35 KT 40 MPH...INLAND 48H 29/1800Z 36.6N 75.0W 45 KT 50 MPH...POST-TROPICAL 72H 30/1800Z 40.0N 66.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 31/1800Z 43.0N 55.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 01/1800Z 47.0N 43.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Brennan |