Tropical Cyclone Discussion
438 WTPZ43 KNHC 011448 TCDEP3 Hurricane Rachel Discussion Number 18 NWS National Hurricane Center Miami FL EP182026 800 AM MST Thu Oct 01 2026 Satellite images show that Rachel continues to produce deep convection with cold cloud tops near -80 to -85C. GLM lightning data also depicts increased lightning activity in the inner core of the storm. An AMSR3 microwave pass that arrived shortly after the previous advisory indicated that the low-level center was slightly farther east within the deep convection and, while there still was some tilt between the low- and mid-level core, the inner structure is becoming better defined, particularly on the southern side of the circulation. Satellite intensity estimates have increased slightly and vary depending on where the low-level center is placed. The subjective Dvorak satellite intensity estimate was Data-T 5.0/90 kt with a Final-T of 4.5/77 kt, and the last three DMINT estimates using various microwave images over the past several hours ranged between 88-91 kt. Given the improved structure in the microwave data and current satellite trends, the initial intensity is raised to 90 kt for this advisory. The system continues to move west-northwestward, or 295/5 kt, and this motion is expected to continue at a slightly slower forward speed over the next couple of days. As a trough over the western U.S. lifts northeastward, a mid-level ridge will build to the north of Rachel, and a westward motion at an increased forward speed is expected through the end of the forecast period. There are some along-track differences in the guidance this cycle regarding when the westward acceleration begins, with the GDMI and HCCA moving initially slower than the global models. The NHC track forecast has been slowed down slightly in the short term, and trends toward the HCCA and GDMI aids. Environmental conditions remain generally favorable for strengthening, with warm sea surface temperatures and plenty of mid-level moisture. The only inhibiting factor has been the wind shear that has kept Rachel's strengthening rate more gradual to steady. Although the wind shear had been forecast to lessen, it has not done so, and the latest SHIPS forecast now keeps the shear moderate over the next two days or so. Given the current structure, the NHC forecast indicates continued strengthening for the next day or so, which lies above the model guidance. In about 2-3 days, wind shear is forecast to decrease though the hurricane should encounter drier mid-level air while the system moves almost parallel to the 27C isotherm. These factors should cause a weakening trend but how fast that weakening occurs will be highly dependent on the structure of the system. Additionally, with weak shear and the hurricane paralleling the 27C isotherm, the structure can sometimes become annular, moderating the weakening rate. The latest NHC intensity forecast trends back toward the HCCA intensity aid during the latter part of the forecast period with gradual weakening, although there remains uncertainty at that time range. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 19.6N 109.6W 90 KT 105 MPH 12H 02/0000Z 19.7N 110.1W 95 KT 110 MPH 24H 02/1200Z 19.8N 110.8W 100 KT 115 MPH 36H 03/0000Z 20.0N 111.5W 105 KT 120 MPH 48H 03/1200Z 20.1N 112.5W 100 KT 115 MPH 60H 04/0000Z 20.3N 113.6W 95 KT 110 MPH 72H 04/1200Z 20.4N 114.7W 90 KT 105 MPH 96H 05/1200Z 20.5N 117.2W 85 KT 100 MPH 120H 06/1200Z 20.6N 120.3W 80 KT 90 MPH