Tropical Cyclone Discussion
346 WTPA44 PHFO 072048 TCDCP4 Hurricane Lowell Discussion Number 47 NWS Central Pacific Hurricane Center Honolulu HI EP122026 Issued by NWS National Hurricane Center Miami FL 1100 AM HST Mon Sep 07 2026 The satellite presentation of Lowell has slightly degraded during the past several hours, with the Air Force Hurricane Hunter showing slowly rising central pressures. There is also a tilt on recent microwave imagery due to increasing southwesterly shear, and the low-level center is a bit west of the ragged eye in conventional satellite data. Although the peak flight-level winds at 700 mb were 113 kt, the plane also reported the loss of an eyewall, which suggests the standard 90 percent rule will be too high for a surface wind reduction. Thus, the initial wind speed is set to 95 kt, which also is close to the most recent JTWC and HFO classifications. The initial motion is north-northeastward or 030/15 kt. Lowell's motion should gradually bend leftward due to the steering from a mid- to upper-level low north of Hawaii and a building ridge to the northeast. The latest guidance is almost the same as before, moving the center just west of Niihau tonight, and the new NHC track in the short-term is only nudged slightly eastward. After passing the main Hawaiian Islands, Lowell will likely get wrapped around the aforementioned upper-level low and take a westward turn after 48 hours. At long range, the system could turn northwestward due to a new trough interaction, but hopefully it won't survive due to its weakened state. The new forecast is very similar to the previous one, and south of the latest GFS/ECMWF models. Lowell should slowly weaken today due to increasing shear and decreasing SSTs. A more rapid weakening should occur after it passes Hawaii overnight as shear gets quite high, and it moves over even cooler waters. Model guidance is showing a much weaker system by midweek, and the new NHC forecast follows that trend. Beyond Wednesday, only a gradual loss of strength is forecast due to shear lessening while the system is over marginally warm waters. Lowell could be transitioning to a post-tropical cyclone at day 5, but the possible trough interaction is leading to a wide range of solutions from re-strengthening to a quick dissipation. For now, the forecast will follow the guidance mean, and it should be mentioned this is a low-confidence long-range prediction. KEY MESSAGES: 1. Kauai County: The core of Lowell is forecast to pass near Niihau tonight and early Tuesday, and damaging hurricane conditions are expected during that time, with the highest winds atop mountains and on windward and leeward slopes. Large damaging waves will impact exposed portions of the coastline, producing dangerous coastal flooding and inundation of low-lying areas through early Tuesday. 2. Periods of heavy rainfall will increase in coverage over the Hawaiian Islands today and continue through Wednesday. This may produce significant flash flooding and mudslides, especially across Kauai County and portions of the Big Island. 3. Oahu: Tropical storm conditions are expected to begin tonight. Strong, damaging wind gusts could cause tree damage and power outages, especially in areas of higher terrain. 4. Large swells will produce life-threatening surf and rip current conditions during the next several days across portions of the Hawaiian Islands. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 18.7N 161.8W 95 KT 110 MPH 12H 08/0600Z 20.9N 161.1W 85 KT 100 MPH 24H 08/1800Z 23.8N 160.8W 65 KT 75 MPH 36H 09/0600Z 25.9N 161.1W 55 KT 65 MPH 48H 09/1800Z 27.5N 162.4W 50 KT 60 MPH 60H 10/0600Z 27.9N 164.8W 45 KT 50 MPH 72H 10/1800Z 27.6N 167.4W 40 KT 45 MPH 96H 11/1800Z 27.6N 171.0W 40 KT 45 MPH 120H 12/1800Z 30.0N 172.0W 35 KT 40 MPH