ZCZC HFOTCDCP3 ALL
TTAA00 PHFO DDHHMM
 
Tropical Storm Miriam Discussion Number  28
NWS Central Pacific Hurricane Center Honolulu HI   EP152018
500 PM HST Sat Sep 01 2018
 
The satellite presentation of Miriam continues to steadily
deteriorate under the effects of 45 to 55 kt of southwesterly
vertical wind shear. The center has been completely exposed during
daylight hours, and a diminishing cluster of deep convection in the
north quadrant has been pushed off to more than 100 n mi from the
center. Subjective Dvorak current intensity estimates range from
2.5/35 kt from JTWC and SAB to 3.0/45 kt from HFO. Final T numbers
from all agencies are lower, and CIMSS ADT yielded an estimate of 32
kt. Given these inputs and an 1844Z ASCAT-A pass that showed wind
retrievals near 45 kt, the initial intensity is lowered to 40 kt.
The ASCAT-A pass was also used to adjust the wind radii.

The initial motion is north-northwest (330 degrees) at 11 kt. A mid
to upper level trough to the northwest of Miriam will continue to
produce very strong vertical wind shear during the next couple of
days. As Miriam becomes increasingly shallow under the effects of
the shear, the system will be steered toward the northwest under a
greater influence of a deep ridge located far to the northeast. Once
the turn is made tonight, the general northwestward motion will
persist through dissipation on Monday. The forecast track was nudged
to the left of the prior advisory and lies near the middle of the
guidance envelope near TVCE and HCCA. Under the hostile vertical
wind shear and decreasing SSTs, Miriam is expected to weaken to a
post-tropical remnant low on Sunday. The official forecast weakens
Miriam rather quickly, though at a slightly slower rate than almost
all guidance, and is closest to AVNI.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0300Z 24.2N 142.3W   40 KT  45 MPH
 12H  02/1200Z 25.6N 143.6W   35 KT  40 MPH
 24H  03/0000Z 27.0N 145.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  03/1200Z 28.2N 147.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  04/0000Z...DISSIPATED
 
$$
Forecaster Wroe
 
NNNN