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Hurricane Lane Discussion Number  38
NWS Central Pacific Hurricane Center Honolulu HI   EP142018
500 PM HST Thu Aug 23 2018
 
The weakening trend is underway. Over the past several hours, the 
CDO of Lane has become elliptical as strong shear, 25 to 35 kt in 
the UW-CIMSS shear analysis, begins to impinge on the core of the
hurricane. Outflow has become very restricted in the southwest The
eye, while still clearly evident on radar, is becoming indistinct in
the visible and infrared satellite imagery. The satellite intensity
estimates from HFO, JTWC, TAFB and SAB were a unanimous 5.5, and the
CIMSS FT number was 5.6 with the CI being held up by constraints.
Based the current intensity of 105 kt on these estimates.

The initial motion estimate is 330/5. There is no change to the 
forecast philosophy with this package. Lane continues to be steered 
toward the north on the western side of a mid-level ridge which is 
located to the east of Hawaii. The consensus guidance continues to 
show a northward motion, or even a motion toward just east of due 
north, as the ridge builds south and possibly southwest of the
cyclone. The official forecast is similar to the previous track, and
remains a bit left of the consensus tracks. As the inner core
continues to deteriorate, Lane will come increasingly under the
influence of the low level easterlies and begin tracking westward.
However, the exact time when this will occur is still rather
uncertain, and only a small delay in this decoupling could bring
Lane farther north, with considerably worse conditions over the
islands. Even if Lane remains along the forecast track, some
significant impacts are expected. 

Our intensity forecast shows weakening, but continues to trend on
the high side of the intensity guidance through 72 hours owing to
how organized Lane's core has been in recent days. During the later
periods of the forecast, it is possible that Lane will not survive
the shear and may become a remnant low even sooner than forecast. 
 
 
KEY MESSAGES:
 
1. It is vital that you do not focus on the exact forecast track or
intensity of Lane, and remain prepared for adjustments to the
forecast. Although the official forecast does not explicitly
indicate Lane's center making landfall over any of the islands, this
remains a very real possibility. Even if the center of Lane remains
offshore, severe impacts could still be realized as they extend well
away from the center.
 
2. Lane will pass dangerously close to the main Hawaiian Islands as
a hurricane on Friday, and is expected to bring damaging winds.
Terrain effects can cause strong localized acceleration of the wind
through gaps and where winds blow downslope. These acceleration
areas will shift with time as Lane passes near or over the islands.
Winds will also be stronger at the upper floors of high rise
buildings.
 
3. The slow movement of Lane also greatly increases the threat for
prolonged heavy rainfall and extreme rainfall totals. This is
expected to lead to major, life-threatening flash flooding and
landslides over all Hawaiian Islands.
 
4. Large and damaging surf can be expected along exposed
shorelines, especially along south and west facing coasts, with
localized storm surge exacerbating the impacts of a prolonged period
of damaging surf. This could lead to severe beach erosion.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0300Z 17.8N 157.9W  105 KT 120 MPH
 12H  24/1200Z 18.7N 157.9W   95 KT 110 MPH
 24H  25/0000Z 19.6N 158.1W   85 KT 100 MPH
 36H  25/1200Z 20.1N 158.6W   75 KT  85 MPH
 48H  26/0000Z 20.3N 159.6W   65 KT  75 MPH
 72H  27/0000Z 20.2N 162.4W   55 KT  65 MPH
 96H  28/0000Z 20.8N 165.1W   35 KT  40 MPH
120H  29/0000Z 23.2N 167.3W   30 KT  35 MPH
 
$$
Forecaster R Ballard
 
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