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| #909540 (Received by flhurricane at: 3:53 AM 08.Nov.2017) TCDAT4 Tropical Storm Rina Discussion Number 9 NWS National Hurricane Center Miami FL AL192017 500 AM AST Wed Nov 08 2017 Satellite imagery over the past 6 hours indicates that Rina has taken on a tight comma-cloud appearance, more indicative of a sub-tropical cyclone than a tropical system. Although an eye-like feature has recently developed, it appears to be tilted about 20-30 nmi to the north of the low-level center. Dvorak satellite intensity estimates were ST3.0/45-50 kt from TAFB and T3.5 from SAB. Data from a late-arriving, partial ASCAT-B scatterometer pass at 0029Z indicated 46-kt surface winds well east of the center, and the cloud pattern has improved since that time. Based these data, the intensity of Rina has been increased to 50 kt. Rina is moving northward or 010/17 kt. Rina is located just north of the axis of a deep-layer ridge, which is located to the east of the cyclone. As a result, a northward to north-northeastward motion is expected for the next 12-24 h. Thereafter, a shortwave trough situated to the southwest of Rina should induce acceleration toward the northeast on Thursday, followed by a more rapid motion of 30-35 kt by Thursday night and Friday as westerly flow on the east side of a deep-layer trough captures the system. The latest NHC model guidance has shifted to the west some, but the official forecast track has only been nudged slightly in that direction due to a distinct westward bias noted in the model guidance during the past 48 hours. Although some sight strengthening could occur during the next 6-12 hours, the overall intensity trend is forecast to change little during the period due to the combination of cold SSTs of less than 20 deg C by 18 h and increasing vertical wind shear of more than 35 kt by 36 hours. By 24 h, Rina should become a post-tropical cyclone over the cold waters of the far north Atlantic and become extratropical and merge with a front by 48-72 h. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 37.1N 48.4W 50 KT 60 MPH 12H 08/1800Z 39.7N 47.7W 50 KT 60 MPH 24H 09/0600Z 43.6N 45.7W 50 KT 60 MPH...POST-TROPICAL 36H 09/1800Z 48.7N 40.6W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 10/0600Z 53.3N 32.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 11/0600Z...DISSIPATED $$ Forecaster Stewart |
