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 784 
 WTPA45 PHFO 092128
 TCDCP5
  
 Hurricane Olivia Discussion Number  37...Corrected
 NWS Central Pacific Hurricane Center Honolulu HI   EP172018
 1100 AM HST Sun Sep 09 2018
 
 Correction to 2nd paragraph to include mention of ongoing synoptic
 reconnaissance mission.
 
 There are conflicting signals in the aircraft reconnaissance data
 and the satellite imagery this morning. Over the past few hours, a
 persistent eye feature has redeveloped and deep convection has
 been blowing up around the center. In fact, Dvorak Data-T numbers
 climbed back up to 4.5 from all 3 satellite fix agencies. However,
 the highest flight level wind was only 65 kt, and the SFMR winds
 were even lower. Given Olivia's recent improved presentation on
 satellite and a central dropsonde pressure of 988 mb, I would be
 hard-pressed to lower the intensity below hurricane strength, and
 decided instead to leave the current intensity at 65 kt, but this is
 somewhat uncertain and may be generous. 
 
 The initial motion estimate is 270/12. The forecast philosophy has
 not changed, although the devil is in the details. Olivia is moving
 to the south of a deep layer ridge which is building westward in
 tandem with the tropical cyclone. Stronger ridging is expected to
 develop west of Olivia in about 48 hours, sending the system on a
 slightly more south of due west, or west-southwest track. The
 consensus guidance remains fairly tightly clustered and changed
 little with this advisory. However, there are some plausible
 outliers, like the ECMWF which is on the north side of the guidance
 and has actually shifted a bit northward once again. The GFS remains
 on the southern side of the guidance spread. This uncertainty speaks
 to the need to not focus on the exact forecast track as Olivia
 moves across the islands. The U.S. Air Force Reserve Hurricane
 Hunters are currently flying another synoptic mission to better
 assess the steering flow around Olivia. 
 
 Olivia is slowly moving toward warmer, though still marginal, sea
 surface temperatures and is in an environment of weak shear.
 This is expected to maintain intensity through the next 36 hours,
 perhaps with additional fluctuations. Shear is expected to start
 increasing over the tropical cyclone in 36 to 48 hours as an upper
 level trough north of the main Hawaiian Islands builds south. This
 should start to impart a weakening trend, which will be gradual at
 first, then more rapid in the days 3-5 period. Our intensity
 forecast remains on the higher side of a tightly clustered guidance
 envelope.
 
  
 KEY MESSAGES:
  
 1.  It is important to not focus on the exact forecast track and
 intensity when planning for Olivia. Persons on all the main Hawaiian
 Islands should continue to monitor the progress of Olivia, and use
 this time to prepare for the increasing likelihood of direct impacts
 from this system this week.
  
 2.  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 winds and
 rainfall, even well away from the tropical cyclone center.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  09/2100Z 21.7N 145.1W   65 KT  75 MPH
  12H  10/0600Z 21.7N 146.7W   65 KT  75 MPH
  24H  10/1800Z 21.7N 148.5W   65 KT  75 MPH
  36H  11/0600Z 21.4N 150.5W   65 KT  75 MPH
  48H  11/1800Z 21.1N 152.5W   60 KT  70 MPH
  72H  12/1800Z 20.2N 157.1W   50 KT  60 MPH
  96H  13/1800Z 19.2N 162.3W   40 KT  45 MPH
 120H  14/1800Z 19.6N 167.3W   30 KT  35 MPH
  
 $$
 Forecaster R Ballard
  
 
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