Tropical Cyclone Discussion
139 WTPA44 PHFO 100232 TCDCP4 Tropical Storm Lowell Discussion Number 56 NWS Central Pacific Hurricane Center Honolulu HI EP122026 Issued by NWS National Hurricane Center Miami FL 500 PM HST Wed Sep 09 2026 Lowell's convective structure on satellite imagery is not very impressive, consisting of a well-defined low-level swirl with some colder cloud tops attempting to form on the northeast side of the circulation. The storm is clearly being negatively impacted by moderate westerly shear importing nearby dry air and marginally warm sea-surface temperatures. Scatterometer data received after the prior advisory indicated a robust surface wind field remains, with peak wind-retrievals in the 45 to 50 kt range. However, subjective and objective satellite estimates continue to decrease, and assuming the low-level circulation continues to spin down without much deep convection, the initial intensity is set to 45 kt for this advisory. The tropical cyclone has turned westward, with the estimated motion now 280 degrees at 12 kt. Lowell is now being steered primarily by a low- to mid-level ridge located north of the tropical storm, and this should maintain a general westward motion over the next 24-36 h. After that time, a mid- to upper-level trough located northwest of Lowell is anticipated to cutoff and interact with the cyclone, with the track guidance coming into better agreement that this will lead to a sharp turn to the northwest or north in 60-72 h. By the end of the forecast period, the upper-level cutoff low moves east of Lowell, leaving behind a shallow low-level circulation sandwiched between two low-level ridges. The track guidance responds to this change by indicating a slow southward drift as the cyclone becomes a remnant low. The NHC track forecast is very similar to the prior one for the first 2-3 days, but shows a sharper turn southward by the end of the forecast. This track is closest to the Google DeepMind (GDMI) and HFIP Corrected Consensus Approach (HCCA) aids. Moderate westerly vertical wind shear, abundant dry air, and only marginally warm sea-surface temperatures are likely to lead to further weakening over the next 36 h. In fact, Lowell could struggle to produce enough convection to be considered a tropical cyclone during this period. Nonetheless, the aforementioned trough interaction in the 2-3 day time frame will likely reinvigorate some convection on the storm's down-shear side via baroclinic processes, which could help intensify Lowell's wind field. Most of the intensity guidance shows at least some intensification during this period of interaction, and the NHC intensity forecast was adjusted somewhat to reflect this solution, though it remains below the HAFS-A/B hurricane models. After 72 h, the upper-level low interacting with Lowell will pass it to the east, leaving the storm in an area of enhanced subsidence that will likely diminish the remaining convection when the storm will be over sub-26 C SSTs. Thus, the latest NHC forecast still shows Lowell becoming a post-tropical low in 96 h. There is still a healthy amount of track uncertainty towards the end of the forecast, though the guidance is coming into better agreement on Lowell losing its tropical characteristics by this time. KEY MESSAGES: 1. Post-storm safety: Follow advice of local officials and avoid areas of downed power lines and flooding. Ensure generators are properly ventilated and placed outside at least 20 feet away from dwellings and garages to avoid carbon monoxide poisoning. During clean up, be careful when using chainsaws and power tools. Drink plenty of water to avoid heat exhaustion. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 29.2N 165.1W 45 KT 50 MPH 12H 10/1200Z 29.3N 167.1W 40 KT 45 MPH 24H 11/0000Z 29.2N 169.5W 35 KT 40 MPH 36H 11/1200Z 29.4N 171.2W 35 KT 40 MPH 48H 12/0000Z 30.6N 172.0W 40 KT 45 MPH 60H 12/1200Z 32.2N 172.4W 45 KT 50 MPH 72H 13/0000Z 33.3N 173.4W 40 KT 45 MPH 96H 14/0000Z 32.8N 175.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 15/0000Z 31.6N 175.4W 25 KT 30 MPH...POST-TROP/REMNT LOW