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Tropical Storm Flossie Discussion Number  16
NWS National Hurricane Center Miami FL       EP072019
1100 PM HST Wed Jul 31 2019

An ASCAT-B overpass from 0527 UTC was helpful in locating Flossie's
center and diagnosing the still-asymmetric wind field.  At the
time, the center was located beneath very cold cloud tops of -76
degrees Celsius, but that convection has since faded away due to
the result of ongoing north-northwesterly shear.  Dvorak Current
Intensity numbers, SATCON, and the scatterometer data all support
maintaining the 55-kt initial intensity.

Restrengthening of Flossie is no longer expected.  For the next 3
days, mid-level shear below the outflow layer is likely to continue
disrupting the vortex, and sea surface temperatures will be
gradually falling by about a degree.  This probably means the
cyclone will continue producing bursts of deep convection that favor
the eastern side of the circulation.  Just about every intensity
model either holds a steady intensity or shows slow weakening
during the next few days, with the Florida State Superensemble the
only model really showing any re-intensification (and it's only 5
kt, at that).  The new NHC intensity forecast therefore holds
Flossie's 55-kt intensity through 72 hours, which still ends up
being higher than the model consensus.  On days 4 and 5,
Flossie runs into the teeth of deeper-layer westerly shear near the
Hawaiian Islands, which is likely to cause weakening, if it hasn't
started already.

Flossie has taken on a more west-northwestward trajectory, with an
initial motion of 285/14 kt.  Mid-level ridging to the north of the
cyclone is expected to be stationary but weaken, which should cause
this heading to persist for the next 4 days with some reduction in
speed.  By the end of the forecast period, a deep-layer trough
north of the Hawaiian Islands will influence the steering flow,
causing Flossie to turn northwestward on day 5.  The overall
guidance envelope has shifted slightly northward, thus the new NHC
track forecast is a little north of the previous forecast, most in
line with the HCCA guidance and the TVCX model consensus.

Although models have trended toward a track just north of the
Hawaiian Islands, we want to remind users that 5-day forecast
positions and intensities have average errors of about 200 miles and
20 mph, respectively.  In addition, hazards associated with tropical
storms extend well away from the center of circulation.  Users
should therefore consult local forecasts from the National Weather
Service Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo
for information specific to the Hawaiian Islands.


FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 14.7N 130.2W   55 KT  65 MPH
 12H  01/1800Z 15.3N 132.5W   55 KT  65 MPH
 24H  02/0600Z 16.0N 135.5W   55 KT  65 MPH
 36H  02/1800Z 16.7N 138.5W   55 KT  65 MPH
 48H  03/0600Z 17.4N 141.3W   55 KT  65 MPH
 72H  04/0600Z 18.5N 146.3W   55 KT  65 MPH
 96H  05/0600Z 19.5N 151.0W   50 KT  60 MPH
120H  06/0600Z 22.0N 155.0W   40 KT  45 MPH

$$
Forecaster Berg

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