ZCZC HFOTCDCP3 ALL
TTAA00 PHFO DDHHMM
 
Hurricane Miriam Discussion Number  20
NWS Central Pacific Hurricane Center Honolulu HI   EP152018
500 PM HST Thu Aug 30 2018
 
Deep convection has been pulsing and producing bursts of lightning 
near the center of Miriam today, but after a brief sighting this 
morning, an eye has not reappeared in traditional satellite
imagery. Dvorak current intensity estimates from HFO/SAB/GTW remain
4.5/77 kt, and with little overall change in the satellite
presentation from earlier today, the initial intensity will remain
75 kt for this advisory. 

The initial motion estimate is 350/07 kt. A motion toward the north 
will continue over the next 36 to 48 h, as Miriam is carried by the 
gradient between a deep-layer ridge to the east and a deep-layer 
trough to the north. Decreasing SSTs and increasingly strong 
southwesterly vertical wind shear lie along the forecast path, and 
Miriam's time as a tropical cyclone is limited. Gradual weakening
in the short term is expected to be followed by a more rapid rate
of decay between 24 h and 72 h, and Miriam is expected to become a
post-tropical remnant low on day 3, dissipating by day 5. As Miriam 
weakens, it is expected to turn toward the northwest as it becomes 
shallow and steered by the low-level trade flow. Track model 
guidance is in better agreement as compared to 24 h ago, with the 
GFS shifting markedly poleward over the past several runs, closer
to the other reliable dynamical aids. The CPHC track forecast was 
shifted to the right of the previous and very closely mimics TVCE 
and HCCA. The intensity forecast follows trends presented by all 
reliable guidance. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 16.5N 141.6W   75 KT  85 MPH
 12H  31/1200Z 17.9N 141.4W   70 KT  80 MPH
 24H  01/0000Z 19.7N 141.5W   65 KT  75 MPH
 36H  01/1200Z 21.5N 141.9W   50 KT  60 MPH
 48H  02/0000Z 23.2N 143.0W   40 KT  45 MPH
 72H  03/0000Z 26.6N 146.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  04/0000Z 30.0N 150.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  05/0000Z...DISSIPATED
 
$$
Forecaster Birchard
 
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