ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM Tropical Storm Alvin Discussion Number 11 NWS National Hurricane Center Miami FL EP012019 200 AM PDT Fri Jun 28 2019 Alvin's satellite presentation has begun to degrade overnight with the overall cloud pattern becoming elongated from southwest to northeast. Earlier ASCAT data indicated that the center was located within the southwestern portion of the main convective mass, suggesting that southwesterly shear has caused the system to become less symmetric. Subjective Dvorak T-numbers from SAB and TAFB have started to decrease, and a blend of the various satellite intensity estimates yields an initial wind speed of 60 kt for this advisory. Increasing southwesterly shear and cooler waters ahead of the storm are expected to cause rapid weakening during the next 24 to 36 hours. Since Alvin is a small cyclone, it is likely to suffer from the affects of the hostile environment more quickly. As a result, the NHC intensity forecast calls for a faster rate of weakening than indicated by the statistical SHIPS/LGEM models and is closest to the latest Florida State Superensemble. The cyclone is forecast to degenerate into a remnant low on Saturday and it should dissipate shortly thereafter. The initial motion estimate is 305/13 kt. The track forecast philosophy remains the same as the previous advisory. Alvin should continue to move around the western periphery of a subtropical ridge during the next couple of days, with the weakening cyclone turning more westward and decelerating. The latest NHC track forecast is near the various consensus aids and is essentially an update of the previous official forecast. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 18.0N 116.3W 60 KT 70 MPH 12H 28/1800Z 19.2N 118.0W 55 KT 65 MPH 24H 29/0600Z 20.3N 119.8W 40 KT 45 MPH 36H 29/1800Z 20.9N 121.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 30/0600Z 21.3N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 01/0600Z...DISSIPATED $$ Forecaster Brown NNNN
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