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 547 
 WTPA45 PHFO 102120
 TCDCP5
  
 Hurricane Olivia Discussion Number  41
 NWS Central Pacific Hurricane Center Honolulu HI   EP172018
 1100 AM HST Mon Sep 10 2018
  
 Olivia still has a very well defined low level circulation center, 
 albeit with a somewhat asymmetric wind field. Air Force Reserve 
 Hurricane Hunters confirmed what the 1623 UTC SSMIS and 1849 UTC
 GMI passes showed, that the system lacks a well-organized
 convective core. Recent visible satellite images are showing new
 convective bands developing on the east side of the circulation
 center, however. The initial intensity was lowered to 65 kt based on
 the reconnaissance data. 
 
 The initial motion is estimated to be 270/8. There is no change to 
 the forecast track philosophy for this package, as Olivia is
 steered toward the west by a deep layer ridge to the west through
 north of the cyclone. This will continue to impart a just south of
 due west motion for the next 72 hours. The consensus models remain
 tightly clustered and have not budged. Our track forecast continues
 to reflect a blend of the consensus models and the ECMWF. It is
 worth noting that the last four runs of the GFS have trended north,
 and is now coming into much better agreement with the guidance
 consensus as well. After 72 hours, an upper level low will approach
 Olivia from the north and begin to pull the tropical cyclone on a
 more west-northwestward motion. Even at 120 hours, the guidance is
 fairly tightly clustered, and our track forecast remains very close
 to TVCN, HMON, HWRF, and FSSE.
 
 Olivia remains over marginal sea surface temperatures of about 
 26.5C, but is approaching the edge of a weak shear environment, 
 according the UW-CIMSS analysis. The SSTs will be warming along the 
 forecast track, but the shear will begin gradually increasing soon. 
 Without a strong eyewall or core, weakening should begin fairly
 soon after the shear increases. The intensity forecast continues to 
 maintain Olivia as a hurricane through 12 hours, followed by slow 
 but steady weakening thereafter. Our forecast is on the higher end 
 of the guidance envelope through the first few days, but it is 
 possible that weakening could occur faster due to shear effects and 
 interaction of the circulation with island terrain.
  
 KEY MESSAGES:
  
 1.  Resist the temptation to make comparisons between Hurricane
 Lane and Hurricane Olivia. Although Lane was a stronger tropical
 cyclone near the islands, it did not bring direct core impacts to
 the state. In some areas, Olivia could bring significantly worse
 impacts than were felt by Lane.
 
 2.  It is important to not focus on the exact forecast track and
 intensity when planning for Olivia. Persons on the main Hawaiian
 Islands east of Kauai should finish their preparations for direct
 impacts from this system starting as early as Tuesday night. Those
 impacts could include intense flooding rainfall, damaging winds, and
 large and dangerous surf.
  
 3.  Regardless of the exact track and intensity that Olivia takes
 as it approaches the islands, significant effects often extend far
 from the center. In particular, the mountainous terrain of Hawaii
 can produce localized areas of strongly enhanced wind gusts and
 rainfall, even well away from the tropical cyclone center.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  10/2100Z 21.7N 148.7W   65 KT  75 MPH
  12H  11/0600Z 21.5N 150.1W   65 KT  75 MPH
  24H  11/1800Z 21.3N 152.2W   60 KT  70 MPH
  36H  12/0600Z 21.0N 154.4W   55 KT  65 MPH
  48H  12/1800Z 20.6N 156.8W   50 KT  60 MPH
  72H  13/1800Z 20.1N 161.8W   40 KT  45 MPH
  96H  14/1800Z 20.3N 167.0W   35 KT  40 MPH
 120H  15/1800Z 21.4N 172.2W   30 KT  35 MPH
  
 $$
 Forecaster R Ballard
  
 
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