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Tropical Storm Flossie Discussion Number   9
NWS National Hurricane Center Miami FL       EP072019
500 AM HST Tue Jul 30 2019

Convection associated with Flossie increased overnight, and the
cyclone's cloud-top pattern has become more symmetric. However, AMSR
data from about 6 hours ago indicated that most of the deep
convection was limited to the southern semicircle of the cyclone,
indicative of northerly shear, and an SSMIS pass at 1213 appeared to
confirm that this is still the case. The latest Dvorak intensity
estimates from TAFB and SAB are 55 kt and 65 kt, respectively, so
the initial intensity of Flossie has been increased to 60 kt, as a
compromise of those two assessments.

Overall, there is little change in the track or intensity forecast
reasoning. Flossie is moving westward on the south side of a broad
mid-level ridge that extends across most of the eastern Pacific.
All of the guidance indicates that Flossie will move generally
west-northwestward for the next 5 days, and the model spread is low.
 Very little changes were made to the NHC track forecast which is
near the various multi-model consensus aids, and confidence in the
track forecast is high.

Conversely, there is low confidence in the intensity forecast.
Flossie appears to have about 36 to 48 hours in a marginally
conducive environment to intensify, and the HWRF even explicitly
forecasts that rapid intensification could occur. An increase in
northerly shear in about 48 h could then inhibit further
intensification, however the GFS and ECMWF suggest that the shear
could decrease again by the end of the forecast period. The spread
in the intensity guidance is very high, particularly beyond 48 h,
with the dynamical models generally higher than the statistical
guidance. No major changes were made to the intensity forecast,
which is near HCCA and FSSE at all forecast hours, however larger
changes could be required in future advisories given the high
uncertainty in the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 12.2N 120.5W   60 KT  70 MPH
 12H  31/0000Z 12.5N 122.5W   70 KT  80 MPH
 24H  31/1200Z 13.1N 125.0W   85 KT 100 MPH
 36H  01/0000Z 13.8N 127.6W   90 KT 105 MPH
 48H  01/1200Z 14.6N 130.3W   95 KT 110 MPH
 72H  02/1200Z 16.1N 136.0W   90 KT 105 MPH
 96H  03/1200Z 17.3N 141.7W   90 KT 105 MPH
120H  04/1200Z 18.5N 147.0W   80 KT  90 MPH

$$
Forecaster Zelinsky

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