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Tropical Storm Miriam Discussion Number  29
NWS Central Pacific Hurricane Center Honolulu HI   EP152018
1100 PM HST Sat Sep 01 2018

The latest estimates from UW-CIMSS and SHIPS indicate Miriam is
being hammered by 50 to 60 kt of southwesterly vertical wind
shear. As a result, the totally exposed and well defined low-level
circulation center (LLCC) is evident in infrared satellite imagery
this evening. The last hints of deep convection associated with
Miriam are now more than 130 n mi north-northeast of the LLCC.
The latest subjective Dvorak current intensity estimates range from
T2.0/30 kt from JTWC and SAB to T2.5/35 kt from HFO.  Final T
numbers from all agencies are lower, and the CIMSS ADT yielded an
estimate of 26 kt. An ASCAT pass from 0557z showed a large area of
30 kt winds east and northeast of the LLCC. Based on a blend of
these estimates, the initial intensity is lowered to 35 kt for 
this advisory.
 
The initial motion is 330 deg / 11 kt. A broad mid- to upper-level
trough to the northwest of Miriam will maintain the 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 likely be steered more toward the northwest under a
greater influence of a deep ridge located far to the northeast.
Once the turn is made later tonight, the general northwestward
motion will likely persist through Monday. The latest forecast
track is close to the previous advisory, and remains near the 
middle of the guidance envelope and close to the consensus model
guidance, TVCE and HCCA. Under the hostile vertical wind shear and
decreasing SSTs, Miriam will continue weakening. The latest 
intensity forecast weakens Miriam at a slightly slower rate than
almost all of the guidance, and is closest to the GFS model. Note
that Miriam is forecast to be a remnant low by Sunday afternoon or
evening, followed by dissipation on Monday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0900Z 25.3N 142.9W   35 KT  40 MPH
 12H  02/1800Z 26.5N 144.2W   30 KT  35 MPH
 24H  03/0600Z 27.9N 146.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  03/1800Z 29.0N 148.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  04/0600Z...DISSIPATED
 
$$
Forecaster Houston
 
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