[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 021433
TCDAT4

Tropical Storm Katia Discussion Number   5
NWS National Hurricane Center Miami FL       AL122023
200 PM CVT Sat Sep 02 2023

Satellite images indicate the center of Katia is on the southern
side of a large central dense overcast.  Scatterometer data from
this morning indicated maximum winds were at least 40-45 kt, and
the latest TAFB Dvorak estimate was 45 kt.  The initial wind speed
is raised to 45 kt from the last full advisory, similar to the
morning update statement.

Katia continues moving north-northwestward, or 330/10 kt.  The
motion should gradually bend toward the northwest today due to the
storm moving between a large middle- to upper-level low to the west
and a narrow mid-latitude ridge over the eastern Atlantic.  The
northwestward motion is likely to continue until about Monday, when
the system becomes weaker and Katia gets stuck in the low-level
subtropical ridge.  The only notable change to the track forecast is
that it has been adjusted to the east in the short-term due to the
initial position and is very close to the previous one at the end.

The storm is probably near its peak intensity with all models
showing an increase in dry mid-level air near the center later
today.  Combined with moderate southerly shear, this should be
enough to choke off deep convection in Katia's core and cause
gradual weakening.  In about 2 days, the environment becomes quite
dry, which should finish off any remaining thunderstorm activity,
and Katia is forecast to degenerate into a remnant low at that time.
The NHC intensity forecast is raised early on to reflect the higher
initial wind speed and is blended back with the guidance by the end
of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 23.9N  29.7W   45 KT  50 MPH
 12H  03/0000Z 25.1N  30.8W   45 KT  50 MPH
 24H  03/1200Z 26.2N  32.1W   40 KT  45 MPH
 36H  04/0000Z 27.0N  33.5W   35 KT  40 MPH
 48H  04/1200Z 27.6N  34.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  05/0000Z 28.5N  35.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  05/1200Z 29.1N  36.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  06/1200Z...DISSIPATED

$$
Forecaster Blake
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