Issued at 200 AM PDT Sun Oct 26 2025
000 WTPZ43 KNHC 260848 TCDEP3 Tropical Storm Sonia Discussion Number 7 NWS National Hurricane Center Miami FL EP182025 200 AM PDT Sun Oct 26 2025 After experiencing a late afternoon diurnal minimum in convection on Saturday during which the structure of Sonia was rather disorganized and the intensification of the tropical storm halted, deep convection has returned over the center overnight, with a large area of cloud tops colder than -70C. Light to moderate southerly shear appears to be affecting the storm just a bit, with the low-level center situated in the southern half of the convective area. The latest subjective intensity estimates are T3.0/45 kt from TAFB and T3.5/55 kt from SAB. The objective UW-CIMSS numbers have been running in the 40-45 kt range, and the highest ASCAT vector on a recent ASCAT pass was 41 kt. The initial intensity is held at 45 kt based on the above data. Sonia is experiencing about 10-15 kt of southerly vertical wind shear while over sea-surface temperatures (SSTs) of about 27C. The shear and SSTs should remain about the same for the next 12-24 h, but southerly shear is forecast to increase further after that time while SSTs begin to gradually decrease. By 60 hours, shear should be stronger than 20 kt while SSTs fall below 26C. Melissa will also reach a drier airmass after 60 h. The NHC forecast will show slight strengthening over the next 24 h while Sonia remains over lukewarm SSTs and moderate shear. Thereafter, gradual weakening is expected, and Melissa should lose its convection and become a remnant low by day 3. The intensity forecast is at the high end of the guidance suite through the first 36 hours of the forecast, but shows a slightly lower peak intensity compared to the previous NHC forecast. The GFS and ECMWF simulated satellite products show the cyclone losing its convection between 60-72 h, so the NHC forecast will call for Sonia to become a remnant low by hour 72, and gradually dissipate thereafter. Sonia has been moving slightly south of due west (265 degrees) at a slow forward speed of 4 kt. A weakness in a narrow subtropical ridge to the north should cause Sonia to turn toward the west-northwest later today, but still at a very slow forward speed, because the steering currents overall are weak. By Tuesday, as the cyclone weakens, a turn back toward the west with an increase in forward speed is expected as Sonia is steered primarily by the low- level flow. The latest NHC forecast is a tad slower than the previous prediction and lies generally between the latest HFIP Corrected Consensus Approach (HCCA) and Google Deep Mind Ensemble Mean (GDMI). FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 13.4N 119.5W 45 KT 50 MPH 12H 26/1800Z 13.5N 119.9W 50 KT 60 MPH 24H 27/0600Z 13.9N 120.6W 55 KT 65 MPH 36H 27/1800Z 14.3N 121.6W 55 KT 65 MPH 48H 28/0600Z 14.7N 122.8W 45 KT 50 MPH 60H 28/1800Z 14.8N 124.3W 35 KT 40 MPH 72H 29/0600Z 14.9N 126.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 30/0600Z 14.5N 129.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 31/0600Z...DISSIPATED $$ Forecaster Hagen
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