678 
 WTPA42 PHFO 231502
 TCDCP2
  
 Hurricane Lane Discussion Number  36
 NWS Central Pacific Hurricane Center Honolulu HI   EP142018
 500 AM HST Thu Aug 23 2018
 
 
 Lane's satellite appearance has degraded somewhat since the previous
 advisory as southwesterly shear impacts the vertical integrity of
 the cyclone. However, the eye is still evident in traditional
 infrared imagery and remains surrounded by a solid ring of cold
 cloud tops. Water vapor imagery shows Lane's circulation
 becoming elongated, with outflow severely restricted in the
 southwest semicircle. The subjective Dvorak current intensity
 estimates from GTW/TAFB/HFO/SAB ranged from 6.0/115 kt to 6.5/127 kt
 for this advisory, while data-T numbers were as low as 5.5/105 kt.
 Using a blend, the initial intensity for this advisory is set at 115
 kt. 
 
 Lane is currently moving toward the northwest into an increasingly 
 hostile environment between a deep-layer ridge to the east, and a 
 trough aloft to the northwest. The initial motion for this advisory 
 is 320/6 kt, with southwesterly shear estimated to be around
 25 kt by UW-CIMSS. 
 
 The track and intensity forecast are extremely dependent on one 
 another in the current forecast scenario, with Lane expected to
 move generally toward the north while it remains a hurricane, and 
 generally toward the west once it weakens. Confidence in the 
 forecast is reduced because it is uncertain how Lane's core will be 
 impacted by its potential interaction with island terrain, and the 
 subsequent rate of weakening. Regardless of whether Lane's center 
 moves over one of the Hawaiian Islands, an increasing amount of 
 southwesterly shear along the forecast track will lead to 
 significant weakening. If Lane's core were to move over one of the 
 islands as has been consistently depicted by GFS/HWRF, then the 
 cyclone would weaken even more rapidly. EMX2 is on the left side of 
 the guidance and indicates less interaction with island terrain,
 and therefore a slightly slower rate of weakening. 
 
 Based on a preponderance of evidence presented by the guidance, the 
 updated forecast indicates a faster rate of weakening than
 indicated earlier, especially on days 2 and 3. The expectation is
 that Lane will weaken due to the combined and cumulative effects of 
 debilitating shear and the interruption of the circulation due to 
 proximity to the high mountains of Maui and the Big Island. The 
 official intensity forecast now closely follows IVCN, SHIPS and the 
 ECMWF-based SHIPS. The track forecast anticipates this weakening, 
 with Lane turning sharply toward the west on day 3. Until then, the 
 forecast track is shifted slightly to the right of the previous 
 forecast through Friday, bringing Lane northward and very close to
 the Big Island and Maui County. This is similar to the multi-model
 consensus HCCA, which includes GFS and HWRF as weighted members. A
 slow forward speed is expected as this occurs, with Lane then moving
 more quickly toward west as it becomes shallow and carried by the
 low-level trade wind flow. 
 
 NOAA Buoy 51002 to the southwest of the islands is in the path of
 Lane, and recently reported a wind gust to 56 kt and significant
 wave heights near 23 ft. Associated data were used to refine wind
 and seas radii in the northwest quadrant. 
 
 
 KEY MESSAGES: 
 
 1. Lane will pass dangerously close to the main Hawaiian Islands as 
 a hurricane today and Friday, and is expected to bring damaging 
 winds. These winds can be accelerated over and downslope from
 elevated terrain, and will be higher in high rise buildings.
 
 2. The slow movement of Lane also greatly increases the threat for 
 prolonged heavy rainfall and extreme rainfall totals. This is 
 expected to lead to life-threatening flash flooding and landslides 
 over all Hawaiian Islands. 
 
 3. Large and damaging surf can be expected along exposed
 shorelines, especially along south and west facing coasts, with
 localized storm surge exacerbating the impacts of a prolonged period
 of damaging surf.
  
 4. Do not focus on the exact forecast track or intensity of Lane, 
 and be prepared for adjustments to the forecast. Although the 
 official forecast does not explicitly indicate Lane's center making 
 landfall over any of the islands, this could still occur. Even if 
 the center of Lane remains offshore, severe impacts could still be 
 realized as they extend well away from the center.  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  23/1500Z 16.9N 157.4W  115 KT 130 MPH
  12H  24/0000Z 17.9N 157.5W  105 KT 120 MPH
  24H  24/1200Z 19.1N 157.6W   95 KT 110 MPH
  36H  25/0000Z 20.0N 157.8W   75 KT  85 MPH
  48H  25/1200Z 20.3N 158.6W   60 KT  70 MPH
  72H  26/1200Z 20.0N 161.3W   45 KT  50 MPH
  96H  27/1200Z 20.0N 164.0W   40 KT  45 MPH
 120H  28/1200Z 21.5N 166.0W   40 KT  45 MPH
  
 $$
 Forecaster Birchard