ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM Tropical Storm Calvin Discussion Number 22 NWS National Hurricane Center Miami FL EP032023 500 PM HST Sun Jul 16 2023 Calvin is slowly weakening, with diminishing deep convection mainly over the eastern portion of the circulation. Convective banding features have become ill-defined. The current intensity estimate is reduced to 50 kt, based on a blend of subjective Dvorak estimates from SAB and TAFB along with objective SATCON estimates from UW-CIMSS. Calvin is traversing SSTs of around 24 deg C, and although water temperatures should increase slightly while the cyclone approaches Hawaii, drier mid-level air as well as increasingly strong vertical shear should cause gradual weakening over the next couple of days. Nonetheless, the dynamical guidance, such as the HAFS and GFS models, suggests that Calvin will still be producing winds near tropical-storm-force, at least over its northern semicircle, when it nears the Hawaiian Islands. The official intensity forecast is similar to the previous one and is close to the model consensus. The official track forecast and its reasoning are basically unchanged from the previous advisory. A mid-level ridge to the north of the tropical cyclone should maintain a generally westward motion for the next few days. On this track, Calvin should enter the central Pacific basin soon, and move near or over the Big Island of Hawaii early Wednesday. It should then continue westward, becoming post-tropical on Thursday before dissipating. The official forecast remains close to the latest NOAA corrected consensus guidance. While the exact storm track near Hawaii is still uncertain, there is potential for portions of the state to experience some heavy rainfall, dangerous surf and rip current conditions, along with minor wind impacts from Calvin. A Tropical Storm Watch may be required for portions of the main Hawaiian Islands tonight. KEY MESSAGES: 1. Calvin is forecast to approach the Hawaiian Islands during the next couple of days or so, bringing the potential for heavy rainfall and dangerous surf and rip current conditions. A Tropical Storm Watch could be issued for portions of the main Hawaiian Islands tonight. FORECAST POSITIONS AND MAX WINDS INIT 17/0300Z 16.4N 137.9W 50 KT 60 MPH 12H 17/1200Z 16.8N 140.4W 45 KT 50 MPH 24H 18/0000Z 17.3N 144.0W 40 KT 45 MPH 36H 18/1200Z 17.7N 147.7W 40 KT 45 MPH 48H 19/0000Z 18.3N 151.5W 35 KT 40 MPH 60H 19/1200Z 18.8N 155.0W 35 KT 40 MPH 72H 20/0000Z 19.4N 158.6W 30 KT 35 MPH 96H 21/0000Z 20.0N 165.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 22/0000Z...DISSIPATED $$ Forecaster Pasch NNNN