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Tropical Storm Flossie Discussion Number 29
NWS Central Pacific Hurricane Center Honolulu HI EP072019
500 AM HST Sun Aug 04 2019
Strong thunderstorms in Flossie's eastern semicircle persisted for
the first half of the night, prevented from moving over the low-
level circulation center (LLCC) by persistent westerly vertical
wind shear near 25 kt. Those thunderstorms began diminishing
shortly after midnight, and while the LLCC remains obscured by mid-
and high-level cloudiness, it appears poised to make an appearance.
Subjective and objective Dvorak intensity estimates indicate that
Flossie is barely hanging on as a tropical storm, and with the LLCC
becoming increasingly exposed, the initial intensity estimate for
this advisory is lowered to 35 kt.
Without any overnight microwave passes to assist with center-
finding, the initial motion estimate is primarily based on tracking
what can be seen of the LLCC, yielding 280/11 kt. A low- to mid-
level ridge north of the cyclone is expected to support a general
motion toward the west over the next 24-36 hours, especially as
Flossie weakens further and is steered by the low-level trade wind
flow. After that, Flossie will round the western portion of the
ridge, interact with a persistent deep-layer trough northwest of
Hawaii, and dissipate. The updated track forecast was changed
little from the previous, which represented a significant westward
shift, and lies close to the EMXI and HCCA. Given average forecast
error, a Tropical Storm Watch may be required for portions of the
Hawaiian Islands later today.
The gradual spin-down of Flossie is expected to continue as it
draws closer to the Hawaiian Islands, despite SSTs gradually warming
to near 27C. The forecast track takes Flossie into an area of even
greater vertical wind shear, leading to steady weakening, soon
followed by dissipation. The intensity forecast has changed little,
and mimics trends indicated by both the statistical and dynamical
guidance.
FORECAST POSITIONS AND MAX WINDS
INIT 04/1500Z 19.3N 147.8W 35 KT 40 MPH
12H 05/0000Z 19.4N 149.7W 35 KT 40 MPH
24H 05/1200Z 19.7N 152.2W 35 KT 40 MPH
36H 06/0000Z 20.4N 154.8W 30 KT 35 MPH
48H 06/1200Z 21.6N 156.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 07/1200Z...DISSIPATED
$$
Forecaster Birchard
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