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 099 
 WTPA45 PHFO 120855
 TCDCP5
  
 Tropical Storm Olivia Discussion Number  47
 NWS Central Pacific Hurricane Center Honolulu HI   EP172018
 1100 PM HST Tue Sep 11 2018
  
 Olivia's low level circulation center (LLCC) continues to be 
 exposed, with deep convection primarily located in the eastern 
 semicircle due to strong westerly vertical wind shear. Subjective 
 Dvorak current intensity estimates from PHFO/SAB/PGTW ranged from 
 2.0/30 kt to 3.0/45 kt. A blend of this data and an earlier ASCAT 
 pass support lowering the initial intensity to 40 kt for this 
 advisory. 
 
 The motion has been very erratic over the past 12 to 18 hours, and 
 although unclear as to why, it appears to have been modulated by 
 pulses in deep convection. When Olivia accelerated westward this 
 morning, associated deep convection had dissipated, allowing the 
 LLCC to be steered by the low-level trade winds. When deep 
 convection redeveloped this afternoon, the forward motion slowed 
 markedly, allowing a deeper-layer flow to lead to a slower forward 
 speed. The motion estimate for this advisory is 250/7 kt. 
 
 Erratic motion is likely to continue overnight as Olivia encounters 
 terrain, but a general west-southwest motion is expected, with an 
 increase in forward speed. If Olivia's LLCC survives the passage 
 near the island terrain, the center is expected to continue moving 
 toward the west-southwest through 48 hours. A more westward motion 
 is expected to begin by 72 hours and beyond as the deep layer ridge 
 west of Olivia weakens and an mid-level low digs southwest toward 
 the cyclone.
 
 Our intensity forecast operates under the assumption that the LLCC 
 will be intact after emerging to the southwest of Maui and the Big 
 Island. If this occurs, gradual weakening is expected to continue
 in line with all the guidance, which shows moderate to strong shear 
 continuing through the forecast period. Olivia is still expected to 
 become a remnant low within 72 hours, with dissipation expected by 
 day 5, but there is a decent chance this will happen even sooner. 
 
 Key Messages: 
 
 1. Although Olivia is weakening, flooding rainfall, high surf, 
 and damaging winds are expected in the warning area. Significant 
 impacts can occur well away from the center, especially when 
 considering that the mountainous terrain of Hawaii can produce 
 localized areas of strongly enhanced wind gusts and rainfall. 
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  12/0900Z 20.8N 154.6W   40 KT  45 MPH
  12H  12/1800Z 20.2N 156.7W   40 KT  45 MPH
  24H  13/0600Z 19.8N 159.3W   35 KT  40 MPH
  36H  13/1800Z 19.3N 161.8W   30 KT  35 MPH
  48H  14/0600Z 19.0N 164.4W   30 KT  35 MPH
  72H  15/0600Z 19.5N 170.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
  96H  16/0600Z 21.0N 174.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 120H  17/0600Z...DISSIPATED
  
 $$
 Forecaster Birchard
  
 
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