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Tropical Storm EMA

Tropical Storm Ema Discussion Number   2
NWS Central Pacific Hurricane Center Honolulu HI   CP012019
1100 AM HST Sat Oct 12 2019
A ball of deep convection has persisted over the center of the 
tropical storm through the morning, with several microwave passes 
indicating an improved structure - most notably the 1436Z and 1721Z 
SSMI passes. Subjective Dvorak intensity estimates are wide-ranging,
from 2.0/30 kt to 3.5/55 kt, while ADT from UW-CIMSS is 2.7/39 kt.
With a nod to the microwave passes indicating an eye-like feature,
the initial intensity estimate for this advisory has been increased
to 45 kt. 

The initial motion estimate for this advisory is 350/11 kt. The 
increased vertical depth of the cyclone has allowed the south to 
southwest flow aloft (provided by mid- and upper-level ridges to
the northeast and east, respectively) have greater influence on the
short-term track. There is little change to the forecast philosophy
presented earlier, with Ema moving into an area of increasing
southwesterly wind shear after about 24 hours as it moves north of
these ridges, and a sharp trough aloft deepens to its west. This
will lead to weakening of the cyclone that will result in a turn
toward the northwest as it becomes shallow, and increasingly steered
by a surface high centered well to the northeast. The system is
still expected to dissipate over increasingly cooler waters in 48
hours as the vertical wind shear persists. The updated track
forecast is close to the previous, and closely follows the reliable
dynamical guidance. 

The forecast requires a Tropical Storm Watch for portions of the
Papahanaumokuakea Marine National Monument.
INIT  12/2100Z 21.1N 163.9W   45 KT  50 MPH
 12H  13/0600Z 22.0N 165.2W   40 KT  45 MPH
 24H  13/1800Z 23.3N 167.0W   35 KT  40 MPH
 36H  14/0600Z 25.6N 169.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  14/1800Z...DISSIPATED
Forecaster Birchard