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 741 
 WTPA45 PHFO 090302
 TCDCP5
  
 Hurricane Olivia Discussion Number  34
 NWS Central Pacific Hurricane Center Honolulu HI   EP172018
 500 PM HST Sat Sep 08 2018
  
 Olivia lost its well-defined center feature in conventional 
 satellite imagery late this afternoon and now appears as a rather 
 messy asymmetric blob of deep convection. However, SSMI and GMI 
 overpasses at 2349 and 2336 UTC, respectively, showed an eyewall 
 remained, except for a break on the west side, along with a very
 well organized low level circulation. The satellite intensity
 estimates showed some spread, with 4.5 from PHFO and UW-CIMSS ADT,
 4.0 from TAFB and SAB, 3.5 from JTWC. The current intensity was
 lowered to 70 kt based on a blend of these estimates, and
 considering the degradation seen in the satellite imagery over the
 last few hours.
 
 The initial motion estimate is 280/14. Olivia is moving just north 
 of due west, to the south of strong deep layer ridging to the west 
 through north of the tropical cyclone. Little change is
 anticipitated for the first 48 hours or so as this ridging builds 
 westward in tandem with Olivia. After 48 hours, the portion of the 
 ridge to the west of Olivia is forecast to strengthen, shunting the 
 tropical cyclone on a more west-southwest motion. The track
 guidance remains fairly tightly clustered, and this forecast is very
 similar to the previous forecast track, which brings the center of
 Olivia over the main Hawaiian Islands between 72 and 96 hours. A
 more westward motion is expected to resume after Olivia's passage
 through the islands, as the upper ridge retreats westward and the
 circulation center becomes increasingly steered by the lower level
 trades.
 
 Olivia is in a very weak shear environment, but moving over
 marginal sea surface temperatures of 25.5C. The hurricane has
 already traversed the coolest water it was going to encounter, but
 SSTs stay sub-27C until Olivia gets close to the islands. This
 should allow Olivia to only very slowly weaken or maintain intensity
 through the next 24 to 48 hours. Shear should begin to gradually
 increase over Olivia after 48 hours, leading to a slow weakening
 trend, but likely not soon enough to prevent some significant
 impacts to the main Hawaiian Islands.
 
 
 KEY MESSAGES:
 
 1.  It is important to recognize that errors in both forecast track 
 and intensity, particularly at longer time ranges, can be large. 
 While it is too soon to determine the location and magnitude of the 
 worst impacts, all interests in Hawaii should continue to monitor
 the progress of Olivia, and use this time to prepare for the
 increasing liklihood of direct impacts from this system. 
 
 2.  Regardless of the exact track and intensity that Olivia takes
 as it approaches the islands, significant effects often do extend
 far from the center. In particular, the mountainous terrain of
 Hawaii can produce localized areas of strongly enhanced winds and
 rainfall, even well away from the tropical cyclone center.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  09/0300Z 21.8N 140.8W   70 KT  80 MPH
  12H  09/1200Z 22.0N 142.9W   70 KT  80 MPH
  24H  10/0000Z 22.1N 145.3W   70 KT  80 MPH
  36H  10/1200Z 22.1N 147.5W   65 KT  75 MPH
  48H  11/0000Z 22.0N 149.4W   65 KT  75 MPH
  72H  12/0000Z 21.2N 153.5W   55 KT  65 MPH
  96H  13/0000Z 20.1N 158.4W   50 KT  60 MPH
 120H  14/0000Z 19.5N 163.5W   40 KT  45 MPH
  
 $$
 Forecaster R Ballard
  
 
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