533 
 WTPA42 PHFO 220856
 TCDCP2
  
 Hurricane Lane Discussion Number  31
 NWS Central Pacific Hurricane Center Honolulu HI   EP142018
 1100 PM HST Tue Aug 21 2018
  
 Lane remains an impressive hurricane this evening, with a well-
 developed warm eye completely surrounded by persistent cold cloud 
 tops. Outflow remains best to the north through east and is
 slightly restricted elsewhere. Hurricane Hunter aircraft from the
 53rd Weather Reconnaissance Squadron flew through Lane once again
 this evening, shortly after the last forecast package, and found
 winds within the northeast eyewall of 146 kt. Based on this
 observation, a special forecast package was issued strengthening
 Lane to a catagory 5 hurricane. Subjective Dvorak current intensity
 estimates range from 6.5/127 kt (JTWC and SAB) to 7.0/140 kt (PHFO).
 ADT from UW-CIMSS was 132 kt. Based on a blend of aircraft-observed
 central pressures and wind speeds, we will set Lane's initial
 intensity to 140 kt for this package. 
 
 Initial motion for this advisory is 285/8 kt. Lane has been moving 
 generally westward along the southern flank of a mid-level ridge 
 during the past several days. However, this cyclone will soon begin 
 to round the western periphery of this ridge and move into an area
 of relatively light steering flow. This will allow Lane to gain
 latitude as its forward speed diminishes. Lane is forecast to
 continue moving west-northwest tonight, then turn to the northwest
 on Wednesday, and to the north-northwest on Thursday, as it moves
 between the mid-level ridge to the east and a developing upper-level
 trough to the northwest of Hawaii. The track and intensity forecasts
 become increasingly uncertain after this point as most track
 guidance brings Lane very close to the islands, with potential
 interaction between Lane and the mountainous terrain of the islands.
 UW-CIMMS derives 13 kt of vertical shear now and this is forecast to
 increase to 20 to 30 kt at 48 hours, according to ECMWF SHIPS. The
 combination of land interaction and increasing vertical shear leads
 to a weakened Lane being steered to the west by the low-level trade
 wind flow during the later forecast periods.  The new track forecast
 closely follows the previous one and lies between GFS and ECMWF
 along FSSE.
 
 Water temperatures along the forecast track will be 27 to 28
 degrees C, warm enough to support a major hurricane. Any
 significant weakening as Lane draws closer to the Hawaiian
 Islands will likely be due to increasing wind shear. Through the
 next 36 to 48 hours, shear is expected to remain in the 10 to 20 kt
 range, and we expect only slow weakening initially. At 48 hours and
 beyond, the forecast incorporates an expected sharp increase in
 shear as Lane moves closer to the large upper trough to the
 northwest of the main Hawaiian Islands. The new intensity forecast
 is very similar to the previous forecast, situated firmly between
 the EMXI and IVCN ensemble guidance.
 
 
 KEY MESSAGES: 
 
 1. Lane is forecast to move dangerously close to the main Hawaiian 
 Islands as a hurricane Thursday through Saturday, potentially 
 bringing damaging winds and life-threatening flash flooding from 
 heavy rainfall. As Lane is expected to be slow-moving as it nears 
 the islands, it will produce large and damaging surf.
  
 2. As Lane approaches the islands from the southeast, initial 
 impacts will be felt on the Big Island, where a Hurricane Warning
 is in effect. Preparations should be rushed to completion as
 tropical-storm force winds are forecast to arrive by late Wednesday
 or early Thursday. A Hurricane Watch remains in effect for Maui
 County and the island of Oahu, with tropical-storm force winds
 possibly beginning Thursday or Thursday night. 
 
 3. Do not focus on the exact forecast track for Lane, as life- 
 threatening weather conditions extend well away from the center of 
 the hurricane, and impacts could be felt on any of the islands. 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  22/0900Z 14.7N 154.5W  140 KT 160 MPH
  12H  22/1800Z 15.4N 155.6W  135 KT 155 MPH
  24H  23/0600Z 16.6N 156.3W  125 KT 145 MPH
  36H  23/1800Z 17.8N 157.0W  110 KT 125 MPH
  48H  24/0600Z 19.1N 157.6W   95 KT 110 MPH
  72H  25/0600Z 21.0N 159.4W   70 KT  80 MPH
  96H  26/0600Z 21.2N 162.2W   50 KT  60 MPH
 120H  27/0600Z 20.8N 165.3W   40 KT  45 MPH
  
 $$
 Forecaster Powell