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Hurricane Miriam Discussion Number  19
NWS Central Pacific Hurricane Center Honolulu HI   EP152018
1100 AM HST Thu Aug 30 2018
 
Miriam's satellite appearance improved early this morning, when a 
banding type eye appeared in traditional satellite imagery shortly 
after a well-developed eye was evident in a 1326Z GPM microwave 
overpass. Cold cloud tops briefly encircled a portion of the eye, 
but the eye is now cloud-filled once again. Subjective Dvorak 
intensity estimates from HFO/SAB/GTW trended up to 4.5/77 kt, and 
the initial intensity estimate for this advisory has been increased 
to 75 kt. The initial motion estimate is 330/7 kt. 

The window for additional strengthening is expected to soon close
as Miriam moves north into an area of very strong vertical wind
shear and decreasing SSTs. Miriam will move nearly due north in the
deep southerly flow between a ridge to the east and a trough to the 
north. This gradient will also increase vertical wind shear to near 
30 kt in 24-36 h. SSTs currently near 28C will drop below 26C after 
48 h, with the cumulative effects leading to a fairly fast rate of 
weakening after tomorrow. The shallow remnant of Miriam is then 
expected to make a turn toward the northwest, primarily steered by 
the low-level trade wind flow, and is expected to be close to 
dissipation by the end of the forecast period. The official track 
forecast is on the left hand side of the guidance envelope, but has 
been nudged to the right at almost all time frames, to be more in 
line with the TVCE and HCCA ensembles. The intensity forecast 
follows trends presented by all reliable guidance.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 15.7N 141.6W   75 KT  85 MPH
 12H  31/0600Z 17.0N 141.7W   80 KT  90 MPH
 24H  31/1800Z 18.7N 141.5W   75 KT  85 MPH
 36H  01/0600Z 20.4N 141.6W   60 KT  70 MPH
 48H  01/1800Z 22.1N 142.5W   45 KT  50 MPH
 72H  02/1800Z 25.0N 145.0W   35 KT  40 MPH
 96H  03/1800Z 28.0N 149.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  04/1800Z 30.0N 154.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Birchard
 
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