Tropical Cyclone Discussion
099 WTPA42 PHFO 232056 TCDCP2 Tropical Storm Nolo Discussion Number 13 NWS Central Pacific Hurricane Center Honolulu HI EP152026 Issued by NWS National Hurricane Center Miami FL 1100 AM HST Wed Sep 23 2026 The system has continued to become better organized this morning, with tighter curved banding features noted on satellite imagery. The low-level circulation remains on the southeastern side of most of the deep convection. Satellite estimates are rising, and the bulk of the values now show this at or above 35 kt. The initial intensity is set to 35 kt, marking the formation of a tropical storm. Nolo is moving west-northwestward at about 5 kt. There is no change to the synoptic reasoning with a ridge located to the northeast of Hawaii forecast to weaken and push eastward as a mid- latitude trough deepens over the northwestern Hawaiian islands. This pattern is likely to the cause Nolo to slow down tonight and then turn north-northeastward by tomorrow with some increase in forward speed. The trough is forecast to move westward this weekend as the ridge rebuilds north of Hawaii, which should force a sharp leftward turn while the cyclone is close to the Big Island. It really depends on how far northeast Nolo gets before the ridge rebuilds, with the solutions that gain the most latitude in the next few days generally getting closest to Hawaii. Although there has been a small southward shift in the overall guidance on this cycle, there is still a large spread approaching 250 n mi from north-to-south by the weekend. The new forecast is nudged south on this advisory, but it should be considered low confidence. The current disorganized structure would seem to promote only slow strengthening during the next day or so under otherwise favorable environmental conditions. However, the system is likely to develop an inner core on Thursday, which could support rapid intensification given very warm waters, low shear and high mid-level moisture values. Intensity guidance is a little higher than the last cycle, and the NHC forecast is raised slightly from day 3 and beyond, showing a major hurricane near and west of Hawaii. Key Messages: 1. Tropical Storm Nolo is expected to strengthen into a hurricane on Thursday as it moves northward, potentially making its closest approach to the Big Island of Hawaii on Saturday. A Hurricane Watch is now in effect for the Big Island, and residents there should follow advice given by local officials, including evacuating if told to do so. 2. The time to prepare for significant heavy rain and flooding impacts on the Big Island is now, as heavy rain becomes more likely by Thursday and Friday. Periods of heavy rain are likely to continue across the Big Island and Maui through the weekend. Life-threatening, catastrophic flooding and mudslides are possible, especially in areas of steep terrain across the Big Island and Maui. Across the remainder of Hawaii, lesser rainfall totals are expected, with isolated flooding possible. 3. Large and damaging waves are possible along the coast of the Big Island into the weekend. 4. Interests elsewhere in Hawaii should closely monitor the latest forecast updates and ensure that they have their preparedness plan in place. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 14.5N 155.3W 35 KT 40 MPH 12H 24/0600Z 14.7N 155.6W 40 KT 45 MPH 24H 24/1800Z 15.1N 155.6W 50 KT 60 MPH 36H 25/0600Z 15.8N 155.2W 65 KT 75 MPH 48H 25/1800Z 16.7N 154.8W 80 KT 90 MPH 60H 26/0600Z 17.5N 154.8W 90 KT 105 MPH 72H 26/1800Z 17.8N 155.6W 100 KT 115 MPH 96H 27/1800Z 17.6N 158.5W 105 KT 120 MPH 120H 28/1800Z 18.8N 161.8W 100 KT 115 MPH