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Tropical Depression TWELVE-E

Tropical Depression Twelve-E Discussion Number   5
NWS Central Pacific Hurricane Center Honolulu HI   EP122019
500 AM HST Thu Sep 05 2019
Although showers and thunderstorms have increased in coverage near 
the depression overnight, they haven't been persistent over the 
estimated position of the low-level circulation center (LLCC).
Additionally, the lack of banding features indicates that the system
remains poorly organized. Subjective Dvorak intensity estimates from
PHFO/PGTW/SAB are 1.5/25 kt, and are widely separated in their
position estimates. The entirety of these data support maintaining
the initial intensity at 25 kt for this advisory.

The initial motion estimate of 260/8 kt is based on a blend of 
extrapolation and satellite position estimates, with the LLCC 
estimated to be on the north side of the deep convection. Little 
overall change to the track forecast philosophy means that the 
updated official forecast is very close to the previous, with the 
system generally moving west, then west-northwest. The short term 
steering mechanism will be a relatively weak low-level ridge to the 
north, thereby keeping forward motion on the slower side. A 
significant increase in forward speed is expected after 60 hours or 
so as a deep-layer ridge strengthens far north of the main Hawaiian 
Islands. This feature will keep the system on a westward track well 
south of Hawaii, with even the northernmost GFS supporting this 
notion. The official forecast lies near the middle of the most 
reliable guidance, and is based a blend of the HCCA consensus and 

Assuming the depression is able to sustain deep convection over the 
center, the environment appears conducive for strengthening as it 
tracks over 28-29C SST in a relatively light shear environment. In 
the short-term, dry air impinging on the circulation from the north 
may be an inhibiting factor, as well as the lack of initial 
structure, although this could be in the process of changing. The 
updated intensity forecast is close to the previous, and closely 
follows trends presented by SHIPS and IVCN consensus. Increasing 
vertical wind shear in the later periods may preclude strengthening 
to a hurricane.  
INIT  05/1500Z 11.8N 143.1W   25 KT  30 MPH
 12H  06/0000Z 11.8N 144.1W   30 KT  35 MPH
 24H  06/1200Z 11.7N 145.8W   35 KT  40 MPH
 36H  07/0000Z 11.7N 147.4W   40 KT  45 MPH
 48H  07/1200Z 11.8N 149.1W   45 KT  50 MPH
 72H  08/1200Z 12.9N 154.1W   50 KT  60 MPH
 96H  09/1200Z 14.5N 160.5W   55 KT  65 MPH
120H  10/1200Z 16.0N 167.0W   55 KT  65 MPH
Forecaster Birchard