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Tropical Storm Flossie Discussion Number  18
NWS National Hurricane Center Miami FL       EP072019
1100 AM HST Thu Aug 01 2019

Again there has been little change in the structure of Flossie
during the past several hours.  There are ongoing bursts of
convection near the low-level center, and the overall cloud pattern
has a very asymmetric look due to the impact of 15-20 kt of
northwesterly vertical wind shear.  A recent ASCAT overpass showed
several 45-50 kt wind vectors near the center, and based on a
combination of these data and other satellite intensity estimates
the initial intensity will remain 55 kt.

The storm has turned a little to the right with the initial motion
now 290/16.  Other than that, there is little change to the track
forecast philosophy.  The subtropical tropical ridge to the north
should keep Flossie moving generally west-northwestward for the
next 72 h as indicated by the tightly clustered track guidance.  The
guidance spread increases after that, with the regional models
(HWRF, HMON, COAMPS-TC) continuing to take Flossie more westward
toward Hawaii and the global models remaining in good agreement on
Flossie turning northward to the northeast of Hawaii ahead of a mid-
to upper-level trough.  The new NHC track forecast continues to
follow the global model scenario, and the new forecast lies a little
north of the previous forecast due mainly to the initial position
and motion.

Flossie is expected to experience moderate shear during the first 72
h of the forecast period, and the shear is likely to increase after
that time.  The intensity guidance responds to this by showing a
gradual weakening, and the new NHC forecast, which is an update of
the previous forecast, follows the overall trend of the guidance.

It is worth noting that the confidence in the 5-day forecast
position of Flossie is still low, and the average error of track and
intensity forecasts at that range is 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  01/2100Z 16.0N 133.2W   55 KT  65 MPH
 12H  02/0600Z 16.6N 135.6W   55 KT  65 MPH
 24H  02/1800Z 17.2N 138.5W   55 KT  65 MPH
 36H  03/0600Z 17.9N 141.4W   50 KT  60 MPH
 48H  03/1800Z 18.5N 144.1W   50 KT  60 MPH
 72H  04/1800Z 19.3N 149.0W   40 KT  45 MPH
 96H  05/1800Z 21.0N 153.5W   35 KT  40 MPH
120H  06/1800Z 25.0N 155.5W   35 KT  40 MPH

$$
Forecaster Beven

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