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Tropical Storm Akoni Discussion Number   9
NWS Central Pacific Hurricane Center Honolulu HI   EP122019
1100 PM HST Thu Sep 05 2019
 
Disorganized and sporadic showers and thunderstorms continue to 
pulse near Akoni's elongated low-level circulation center (LLCC) 
this evening, but the system does not look like a tropical cyclone 
in latest satellite images. In fact, the preponderance of evidence 
over the past 24-48 hours would lead one to the conclusion that a 
tropical cyclone does not exist, or at the very best, that Akoni is 
a poorly-organized depression. Having said that, subjective Dvorak 
current intensity estimates are 2.5/35 kt from PHFO/SAB/PGTW, and 
the current intensity has been maintained at what is likely a 
conservative 40 kt for this advisory. This is primarily based on an 
ASCAT-C pass earlier today that detected winds to 40 kt in an area 
of thunderstorms east of the assumed center. 

The initial motion estimate is a somewhat uncertain 260/10 kt, with 
increasing doubt as to the actual existence of a LLCC. A low- to 
mid-level ridge will strengthen far north of the system over the 
next couple of days, and track guidance remains fairly tightly 
clustered, especially given the uncertainty surrounding the current 
location, speed of movement and level of organization. If Akoni is 
able to organize, a general track toward the west to west-northwest 
is expected, with increasing forward speed on days 2 and 3 before 
slowing toward the end of the forecast period. The updated track 
forecast is a little south of the previous, indicates a slightly 
faster forward motion, and is close to the TVCN consensus. 

The intensity forecast remains challenging and fairly uncertain,
and for now assumes that the cyclone will be able to break away from
the inter-tropical convergence zone (ITCZ) in which it is embedded.
If Akoni can separate from the ITCZ, conditions seem at least 
marginally favorable for modest strengthening in the short term, 
with warm SSTs and light to moderate shear along the forecast
track. Shear will increase after 72 hours, with the updated
forecast indicating a more rapid rate of weakening at the end of the
forecast period, similar to the IVCN intensity consensus. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/0900Z 11.6N 146.8W   40 KT  45 MPH
 12H  06/1800Z 11.5N 148.3W   40 KT  45 MPH
 24H  07/0600Z 11.5N 150.2W   45 KT  50 MPH
 36H  07/1800Z 11.8N 152.3W   45 KT  50 MPH
 48H  08/0600Z 12.5N 155.1W   45 KT  50 MPH
 72H  09/0600Z 14.4N 161.8W   50 KT  60 MPH
 96H  10/0600Z 16.8N 168.7W   45 KT  50 MPH
120H  11/0600Z 18.0N 174.0W   40 KT  45 MPH
 
$$
Forecaster Birchard
 
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