ZCZC HFOTCDCP1 ALL TTAA00 PHFO DDHHMM Tropical Storm Calvin Discussion Number 24 NWS Central Pacific Hurricane Center Honolulu HI EP032023 500 AM HST Mon Jul 17 2023 Conventional infrared satellite imagery shows that Tropical Storm Calvin's low-level circulation center (LLCC) appears to be partially exposed early this morning. Therefore, the system has crossed longitude 140W into the Central Pacific Hurricane Center (CPHC's) area of responsibility. Scatterometer passes from last evening showed a large swath of winds of 40-45 kt north of the LLCC. The subjective Dvorak satellite classification from PHFO is 55 kt, SAB and JTWC are 35 kt, and TAFB's final fix is 45 kt. Based on these observations, we are maintaining the current intensity at 45 kt for this advisory. Calvin continues to move over cool SSTs of around 24 degrees C, and in a dry and stable environment. In the next 18-24 hours, the SSTs are expected to start gradually increasing as the cyclone begins to move closer to the main Hawaiian Islands. Southerly vertical wind shear will likely increase as Calvin nears the Big Island of Hawaii. This shear combined with entertainment of drier air into the system is expected to cause Calvin to weaken. This scenario would likely result in most of the deep convection (assuming it redevelops in the next day or two) being displaced to the north of the LLCC. The intensity forecast lies near the model consensus, and is similar to the previous official forecast we inherited from the National Hurricane Center (NHC) in Miami, Florida. Note that based on the recent scatterometer passes, we have expanded the wind radii in the northern semicircle. The mid-level ridge to the north of Calvin will likely maintain a relatively rapid westward motion during the next few days. On this track, Calvin will likely move near or over the Big Island of Hawaii Tuesday night and Wednesday. It should then continue moving westward until it dissipates. The official forecast is near the previous NHC forecast, and lies close to the model consensus guidance. KEY MESSAGES: 1. Calvin is forecast to pass very close to the Big Island Tuesday night and Wednesday, bringing a period of heavy rain, high surf and locally strong winds. Calvin is expected to weaken as it moves westward to the south of the other Hawaiian Islands Wednesday and Wednesday night, bringing the potential for some peripheral impacts. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 16.8N 141.4W 45 KT 50 MPH 12H 18/0000Z 17.1N 144.1W 40 KT 45 MPH 24H 18/1200Z 17.4N 147.7W 40 KT 45 MPH 36H 19/0000Z 17.8N 151.4W 40 KT 45 MPH 48H 19/1200Z 18.4N 155.1W 35 KT 40 MPH 60H 20/0000Z 19.0N 158.5W 30 KT 35 MPH 72H 20/1200Z 19.7N 162.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 21/1200Z...DISSIPATED $$ Forecaster Houston NNNN
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Page last modified: Monday, 18-Dec-2023 12:09:58 UTC