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Tropical Storm Flossie Discussion Number  30
NWS Central Pacific Hurricane Center Honolulu HI   EP072019
1100 AM HST Sun Aug 04 2019
 
Under southwesterly vertical wind shear in excess 20 kt, deep
convection continues to pulse in the northeast quadrant of Flossie,
leaving the low-level circulation center (LLCC) exposed. Subjective
Dvorak current intensity estimates ranged from 1.5 (25 kt) from SAB
to 2.5 (35 kt) out of JTWC and HFO, while UW-CIMSS suggested an
intensity of 33 kt. Thus, Flossie will be held as a 35 kt tropical
storm.

The first visible satellite images of the day revealed that the LLCC
was a bit farther south than expected, and the initial motion is now
275/10 kt. The westward motion, which will continue into Monday,
is likely due to the increasingly shallow system being steered by
the low- to mid-level ridge to the north. As the ridge weakens
Monday night, Flossie is forecast to turn toward the west-northwest
near the main Hawaiian Islands and remain on that motion until
dissipation. In light of recent trends and expectation that Flossie
will be shallow, the track forecast was nudged southward again near
TVCN and HCCA toward the middle of the guidance envelope.

The gradual spin down of Flossie is expected to continue as the
system nears Hawaii. An upper-level trough northwest of Hawaii will
remain in place through the next several days, maintaining strong
west-southwest winds aloft. As Flossie moves westward under these
strong upper-level winds, vertical wind shear will increase from
around 20 kt now to more than 30 kt tonight, causing Flossie to
weaken. The intensity forecast was altered little from the prior
advisory and takes Flossie down to a tropical depression by Monday
and a remnant low on Tuesday. The forecast is in line with the
dynamical and statistical guidance but keeps Flossie slightly
stronger in the next 12 to 24 hours than nearly all guidance.

Interests in the main Hawaiian Islands should monitor the progress
of Flossie. The updated track forecast calls for the system to be
near or over portions of the state as a tropical depression late
Monday and Tuesday, but given average forecast errors, a Tropical
Storm Watch remains possible for portions of the state later today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 19.0N 148.5W   35 KT  40 MPH
 12H  05/0600Z 19.1N 150.5W   35 KT  40 MPH
 24H  05/1800Z 19.5N 153.2W   30 KT  35 MPH
 36H  06/0600Z 20.5N 155.5W   30 KT  35 MPH
 48H  06/1800Z 21.5N 157.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  07/1800Z...DISSIPATED
 
$$
Forecaster Wroe
 
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