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 WTPA45 PHFO 111453
 Tropical Storm Olivia Discussion Number  44
 NWS Central Pacific Hurricane Center Honolulu HI   EP172018
 500 AM HST Tue Sep 11 2018
 Hurricane Hunters from the 53rd Weather Reconnaissance Squadron 
 spent most of the night flying through Olivia, sampling the core as 
 well the periphery. Maximum flight level winds of 78 kt were 
 observed in the northwest quadrant fairly early in the evening, but 
 subsequent observations indicated that Olivia is well below 
 hurricane intensity. The surface pressure was gradually rising, and 
 the system exhibited tilt with height, with the low-level center on 
 the south side of the cold cloud tops seen in satellite. 
 Additionally, the observed wind field was rather asymmetric, with 
 winds fairly weak in the southern semicircle. The initial intensity 
 for this advisory is deemed to be 55 kt, and given current
 satellite trends, this may be slightly generous.
 The aircraft center fixes add confidence to the initial motion 
 estimate of 270/9 kt. Olivia is being steered by a mid-level ridge 
 centered to the distant northeast, but a mid-level ridge building
 to the northwest of Olivia will induce a motion toward the west-
 southwest later today. Once this occurs, this motion is expected to 
 persist as Olivia crosses the Hawaiian Islands. The updated track 
 forecast is very close to the previous, especially over the first
 48 hours. In 48 to 72 hours, a low aloft is expected to develop
 north of Olivia, and this development is expected to impart a
 motion toward the west-northwest on days 4 and 5. The official
 forecast is now near the center of the guidance envelope, and is
 close to the multi-model consensus TVCE and GFEX. The along-track
 differences between the GFS and ECMWF were reduced with the arrival
 of the 06Z GFS, adding confidence to the short term forecast track,
 which indicates a slightly faster speed of motion than the previous 
 Moderate shear is expected to continue over the next 48 hours while 
 SSTs increase to 28C. The shear is expected to induce slow
 weakening as indicated by nearly all intensity guidance, with
 interaction with island terrain potentially contributing to
 weakening as well. After Olivia exits the Hawaiian Islands to the
 west in 48 to 72 hours, a cold core low aloft is expected to develop
 north of Olivia. By 96 hours the cold core low and Olivia become
 vertically stacked, potentially resulting in Olivia becoming
 post-tropical. The official intensity forecast indicates this will
 occur by day 5, and closely follows IVCN through the bulk of the
 Key Messages: 
 1. Although Olivia is expected to move over the islands as a
 tropical storm, it could still bring significantly worse impacts
 than recent Hurricane Lane. Those impacts could include intense
 flooding rainfall, damaging winds, and large and dangerous surf.
 2. It is important to not focus on the exact forecast track 
 and intensity when planning for Olivia. Regardless of the track 
 that Olivia takes as it approaches the islands, significant impacts 
 can be expected away from the center. In particular, the
 mountainous terrain of Hawaii can produce localized areas of
 strongly enhanced wind gusts and rainfall. 
 INIT  11/1500Z 21.9N 151.1W   55 KT  65 MPH
  12H  12/0000Z 21.6N 152.9W   50 KT  60 MPH
  24H  12/1200Z 21.1N 155.3W   45 KT  50 MPH
  36H  13/0000Z 20.3N 157.8W   45 KT  50 MPH
  48H  13/1200Z 19.7N 160.2W   40 KT  45 MPH
  72H  14/1200Z 19.3N 164.7W   40 KT  45 MPH
  96H  15/1200Z 20.5N 169.5W   35 KT  40 MPH
 120H  16/1200Z 21.6N 174.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 Forecaster Birchard
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