Tropical Cyclone Discussion
242 WTPA42 PHFO 240252 TCDCP2 Tropical Storm Nolo Discussion Number 14 NWS Central Pacific Hurricane Center Honolulu HI EP152026 Issued by NWS National Hurricane Center Miami FL 500 PM HST Wed Sep 23 2026 Nolo's convective organization has improved slightly during the past several hours, with persistent deep convection within a curved band wrapping into the circulation from the north around the western semicircle. The latest subjective Dvorak intensity estimates from JTWC and HFO are both T2.0/30 kt, while objective intensity estimates range from 30 to 40 kt. Given the improved convective organization and the higher objective estimates, the initial intensity was increased to 40 kt in the 2 PM HST intermediate advisory and is maintained for this advisory. Nolo is moving west-northwestward, with an initial motion of 285/5 kt. A weakening subtropical ridge to the north should allow Nolo to slow down and turn northward tonight into Thursday, followed by a north-northeastward motion as an upper-level trough deepens northwest of the Hawaiian Islands. As the trough moves westward and the subtropical ridge rebuilds north of Hawaii, Nolo is forecast to make a sharp westward turn Friday night into Saturday. The latest GDMI and HCCA guidance has shifted slightly to the left, taking Nolo farther south of the Big Island. The NHC track forecast reflects a blend of the previous forecast and these aids, and shows Nolo passing about 85 n mi south of the Big Island on Saturday, then about 215 n mi south of the smaller Hawaiian Islands during the latter portion of the weekend. However, uncertainty remains regarding exactly when and where the sharp westward turn will occur, with the ECMWF remaining on the right side of the guidance envelope and bringing Nolo closer to the islands. Environmental conditions remain favorable for strengthening, with very warm sea surface temperatures and plenty of mid-level moisture along the forecast track. However, around 10 kt of easterly vertical wind shear may temper the rate of intensification during the next 24 to 36 h. As the shear relaxes and Nolo continues to develop an inner core, a faster rate of intensification is forecast while the cyclone moves northward to north-northeastward during the next couple of days. These conditions could support rapid intensification, and Nolo is forecast to become a hurricane by Thursday night and reach major hurricane strength on Saturday as it passes south of the Big Island. The latest NHC intensity forecast hovers near the upper end of the guidance envelope throughout the forecast period. Key Messages: 1. Tropical Storm Nolo is expected to strengthen into a hurricane by Thursday night as it turns northward, potentially making its closest approach to the Big Island of Hawaii on Saturday. A Hurricane Watch remains 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 plans in place. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 14.7N 155.9W 40 KT 45 MPH 12H 24/1200Z 14.8N 156.0W 50 KT 60 MPH 24H 25/0000Z 15.4N 155.8W 60 KT 70 MPH 36H 25/1200Z 16.2N 155.3W 70 KT 80 MPH 48H 26/0000Z 17.1N 155.0W 80 KT 90 MPH 60H 26/1200Z 17.5N 155.1W 90 KT 105 MPH 72H 27/0000Z 17.4N 156.2W 100 KT 115 MPH 96H 28/0000Z 17.5N 158.6W 105 KT 120 MPH 120H 29/0000Z 18.9N 162.1W 100 KT 115 MPH