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Pacific Tropical Cyclone Outlook for September 5th, 2019

2 Tropical Cyclones continue to churn in both the Eastern and Central Pacific Basin.


Tropical Depression Twelve-E, with maximum sustained winds of 30 mph, expected to become Tropical Storm named Akoni in the coming day and no impacts from Akoni is expected as it continues to pass to the south of the islands. However, stronger trade winds and an increase in showers is expected to go into this weekend and early next week.


Hurricane Juliette, a category 2 hurricane, is expected to continue to dissipate over the next 5 days and no impacts to the islands are expected.


No watches or warnings are in effect at this time associated with both tropical cyclones.

Discussion on Twelve-E (Akoni) as of 5:00 am Thursday:

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 ECMWF. 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. FORECAST POSITIONS AND MAX WINDS 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


Discussion on Hurricane Juliette as of 5:00 am HST, Thursday:

Hurricane Juliette Discussion Number 18 NWS National Hurricane Center Miami FL EP112019 800 AM PDT Thu Sep 05 2019 There has been little overall change in Juliette's cloud pattern this morning. The hurricane still has a large, ragged eye, but the cloud tops within the surrounding ring of convection have warmed during the past couple of hours. Earlier microwave imagery showed a well-defined low-level eye that is located a little south of the satellite fixes from TAFB and SAB. The various satellite intensity estimates range from 77 to 85 kt, so the initial wind speed of 80 kt is maintained for this advisory. Juliette will be moving over gradually lower sea surface temperatures and into a more stable air mass but the vertical shear is expected to remain fairly low during the next couple days. This will likely result in a somewhat slower rate of weakening than is typical for east Pacific hurricanes moving over cool SSTs. Later in the period, southwesterly shear is expected to increase which should cause the cyclone to degenerate into a remnant low in 3 to 4 days. The NHC intensity foreast is closest to the SHIPS intensity model. The initial motion estimate is 305/8 kt. A general northwestward motion around the southwestern portion of the mid-level ridge over the southwestern United States should continue today. A turn toward the west-northwest, and then the west, is expected over the next couple of days as Juliette gradually weakens and is steered by the easterly low- to mid-level flow. The new NHC track forecast is near the middle of the guidance envelope but is a little faster than the previous advisory to be closer to the multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 20.6N 119.9W 80 KT 90 MPH 12H 06/0000Z 21.5N 121.3W 75 KT 85 MPH 24H 06/1200Z 22.6N 123.3W 65 KT 75 MPH 36H 07/0000Z 23.3N 125.4W 55 KT 65 MPH 48H 07/1200Z 23.6N 127.4W 45 KT 50 MPH 72H 08/1200Z 23.6N 131.2W 35 KT 40 MPH 96H 09/1200Z 23.2N 134.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 10/1200Z 23.0N 137.0W 25 KT 30 MPH...POST-TROP/REMNT LOW

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