ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Genevieve Discussion Number 3 NWS National Hurricane Center Miami FL EP122020 1000 PM CDT Sun Aug 16 2020 Infrared (IR) and passive microwave (MW) satellite imagery indicate that Genevieve has continued to rapidly intensify while becoming better organized. A 17/0121Z SSMI/S MW image showed that the cyclone had already developed a 15-nmi-diameter, ragged mid-level eye, while both IR and MW data indicate tight banding features spiraling into a compact inner-core convective region. The initial intensity of 50 kt is based on unanimous T3.0/45 kt satellite classifications from TAFB and SAB, with the aforementioned eye feature nudging upward the final intensity assessment. The initial motion estimate remains west-northwestward or 290/16 kt. The track forecast and reasoning remain unchanged and fairly straightforward. Genevieve is expected to move generally west-northwestward around the southwestern periphery of a sprawling deep-layer ridge located over the western United States and northern and central Mexico throughout the forecast period. The new NHC track forecast is very similar to the previous advisory track, and lies near the middle of the tightly packed consensus track model forecasts. Now that Genevieve has developed a tight inner-core wind field and an eye feature, it isn't a question of will the cyclone rapidly strengthen, but rather how quickly and how much will the strengthening be! The deep-layer and mid-level vertical wind shear parameters are forecast to be weak at less than 5 kt through 72 hours, while the upper-level outflow pattern is expected to steadily improve during that time, including the development of dual outflow channels to the north and south. These very favorable atmospheric conditions will coincide with a very moist mid-level regime and sea-surface temperatures (SST) of at least 30 deg C. As a result, the intensity forecast has been nudged upward, with rapid intensification (RI) of about 30 kt expected during next 24 h, followed by a slightly faster rate of RI in the 24-48 hour time frame when the dual outflow channels will be present. By 60-72 hours, Genevieve is expected to be moving over shallower warm water, which should result in significant cold upwelling and the onset weakening. More rapid weakening is forecast thereafter due to the cyclone moving over 23-25 deg C SSTs. The official intensity is near the upper end of the guidance envelope, but remains below the ECMWF-based SHIPS model forecast which brings Genevieve to near 130 kt in 48-60 hours. Although the tropical cyclone is forecast to remain well offshore of the southern coast of Mexico, large swells generated by the strengthening system are expected to begin affecting portions of the coast of southern Mexico over the next day or so. FORECAST POSITIONS AND MAX WINDS INIT 17/0300Z 12.4N 100.4W 50 KT 60 MPH 12H 17/1200Z 13.4N 102.7W 60 KT 70 MPH 24H 18/0000Z 14.8N 105.7W 75 KT 85 MPH 36H 18/1200Z 16.3N 108.2W 95 KT 110 MPH 48H 19/0000Z 17.7N 110.1W 115 KT 130 MPH 60H 19/1200Z 19.1N 111.5W 120 KT 140 MPH 72H 20/0000Z 20.4N 112.9W 105 KT 120 MPH 96H 21/0000Z 22.7N 116.0W 80 KT 90 MPH 120H 22/0000Z 24.7N 119.7W 55 KT 65 MPH $$ Forecaster Stewart NNNN