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Tropical Depression Fifteen-E Discussion Number  12
NWS Central Pacific Hurricane Center Honolulu HI   EP152026
Issued by NWS National Hurricane Center Miami FL
500 AM HST Wed Sep 23 2026

Satellite imagery shows that the depression is becoming better 
organized.  Banding features are becoming more defined on the 
western and northern sides of the system, with expanding outflow 
noted.  However, the low-level circulation appears to be on the 
southeastern edge of the deep convection and isn't well aligned 
with the deep convective mass.  Satellite intensity estimates have 
a large spread this morning, from about 25-40 kt.  Without 
definitive evidence it has become a tropical storm, the initial wind 
speed will stay 30 kt, which is also consistent with winds from a 
recent OSCAT scatterometer pass.

The depression has slowed since the last advisory and seems to be 
moving west-northwestward at about 5 kt.  A ridge to the northeast 
of Hawaii is forecast to weaken and slide eastward as a mid- 
latitude trough drops over the northwestern Hawaiian islands.  
This evolution is likely to the cause the cyclone to slow down 
later today or tonight and then turn northward or 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 westward turn 
while the cyclone is close to the Big Island.  At this time frame, 
it is impossible to know exactly when that turn will happen and, 
unsurprisingly, there is a large north-south spread in the guidance. 
Our best guidance is on the northern side of the track envelope, 
and new NHC forecast remains essentially the same as the last 
advisory.  Interests in the Hawaiian Islands, especially on the Big 
Island, should closely monitor the system, with life-threatening 
catastrophic flooding possible over the steep terrain on this track.

The depression should intensify slowly at first, given the current 
structure of the low-level center not co-located with the mid-level 
circulation as seen on satellite.  However, after the system 
develops an inner core, the environment seems conducive for 
significant strengthening, with low shear, high mid-level moisture 
and SSTs from 28-29C.  The rapid intensification probabilities are 
increasing, and the best model guidance is showing this as a major 
hurricane in a few days.  Given the environment and the 
best-performing aids (Google DeepMind and HCCA) again showing 
major-hurricane strength, the NHC forecast is raised from the 
previous one and shows the cyclone as a major hurricane when it 
approaches the Big Island of Hawaii by the weekend.
 
Key Messages:
 
1. Tropical Depression Fifteen-E is expected to strengthen into a 
tropical storm later today and a hurricane on Thursday as it turns 
northward, potentially making its closest approach to the Big Island 
of Hawaii on Saturday. There is an increasing risk of wind and wave 
impacts in the Hawaiian Islands, and a Hurricane Watch may be 
required for the Big Island later today.

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. Interests 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  23/1500Z 14.5N 154.4W   30 KT  35 MPH
 12H  24/0000Z 14.7N 155.2W   40 KT  45 MPH
 24H  24/1200Z 15.0N 155.5W   50 KT  60 MPH
 36H  25/0000Z 15.7N 155.2W   65 KT  75 MPH
 48H  25/1200Z 16.7N 154.8W   80 KT  90 MPH
 60H  26/0000Z 17.6N 154.5W   90 KT 105 MPH
 72H  26/1200Z 18.2N 154.7W  100 KT 115 MPH
 96H  27/1200Z 18.1N 157.0W  100 KT 115 MPH
120H  28/1200Z 18.7N 160.2W   95 KT 110 MPH
 
$$
Forecaster Blake
 
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