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Tropical Storm Flossie Discussion Number   4
NWS National Hurricane Center Miami FL       EP072019
1100 PM HST Sun Jul 28 2019

Over the past several hours, deep convection has developed near the
center of circulation with a large curved band composed of
cloud tops as cold as -80 C enveloping the western semicircle of the
cyclone. A recent ASCAT-C scatterometer pass partially captured the
northeastern quadrant of the system and measured winds of 30 kt
over 75 n mi from the center and it is likely that higher winds were
occurring at that time in the unsampled area closer to the center.
In addition, the mean of the subjective Dvorak satellite intensity
estimates have increased to tropical storm force and therefore the
depression has been upgraded to Tropical Storm Flossie with an
initial intensity of 35 kt.

The initial motion is 275/17 kt. Ridging will persist north of the
cyclone throughout the next several days which will continue to
steer it west to west-northwestward with some decrease in
forward speed by later today as the ridge weakens slightly. The
track guidance is in very good agreement and the official NHC
forecast track is similar to the previous forecast which is very
near the center of the consensus aids.

The environment around Flossie is favorable for strengthening over
the next 72 hours or so, and if the current deep convection can
persist near the center today during the diurnal minimum, then the
inner core of the cyclone will likely become well established over
the next 24 hours. This would allow for steady strengthening to
occur, with Flossie becoming a hurricane sometime on Tuesday.
Although not implicitly shown in the forecast, it is possible that
Flossie could undergo rapid intensification during the next 72 hours
which could result in intensities higher than currently forecast at
those time frames. By day 4, the cyclone is forecast to move
over marginal sea surface temperatures and into a drier, more
stable environment while undergoing increasing northwesterly shear.
This should result in a weakening trend beginning around hour 96
of the forecast period. The official NHC intensity forecast was
changed little from the previous forecast, and remains on the
higher end of the intensity guidance.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 12.5N 113.0W   35 KT  40 MPH
 12H  29/1800Z 12.7N 115.6W   45 KT  50 MPH
 24H  30/0600Z 12.6N 118.5W   55 KT  65 MPH
 36H  30/1800Z 12.8N 121.1W   65 KT  75 MPH
 48H  31/0600Z 13.3N 123.7W   75 KT  85 MPH
 72H  01/0600Z 14.5N 128.9W   95 KT 110 MPH
 96H  02/0600Z 15.8N 134.5W   95 KT 110 MPH
120H  03/0600Z 17.5N 140.5W   90 KT 105 MPH

$$
Forecaster Latto/Pasch

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