Tropical Storm Katia Forecast Discussion Number 7

By | September 3, 2023

WTNT44 KNHC 030236

Tropical Storm Katia Discussion Number   7
NWS National Hurricane Center Miami FL       AL122023
300 AM GMT Sun Sep 03 2023

Katia has noticeably weakened since the previous advisory.  Remnants
of convection appear to be separating from the low-level circulation
and no new bursts have formed in the past few hours.  Geostationary
satellite imagery suggests dry air likely has made its way into the
core of the storm.  Final T-numbers from TAFB and SAB were T3.0/45
and T1.5/25 .  The initial intensity has therefore been lowered to
40 kt.  Scatterometer data missed the center of the storm, but
measured the winds on the eastern half, revealing the radii of
tropical-storm-force winds had decreased.

Katia is once again moving north-northwestward at about 14 kt.  The
storm should turn back to the northwest shortly as it moves between
an upper-level low to the west and a narrow mid-latitude ridge over
the eastern Atlantic.  Model guidance suggests it should maintain
this heading at a decreased forward speed during the next couple of
days.  However, the cyclone has been moving to the east of the track
guidance envelope for the past several advisory cycles.  Beyond day
2, there is still considerable uncertainty in the motion, and
therefore location, of Katia or its remnants.  The latest NHC track
forecast has been shifted northward, largely due to the initial
storm position.

Model guidance still suggests Katia may have another burst of 
convection later today or Monday.  Environmental conditions are 
expected to become increasingly unfavorable, with strong-to-moderate 
vertical wind shear and dry mid-level humidities.  The official 
intensity forecast still shows gradual weakening through the 
forecast period and shows Katia becoming a remnant low in a couple 
of days, though this may occur sooner.


INIT  03/0300Z 26.5N  31.0W   40 KT  45 MPH
 12H  03/1200Z 27.5N  32.0W   35 KT  40 MPH
 24H  04/0000Z 28.3N  33.1W   30 KT  35 MPH
 36H  04/1200Z 28.9N  34.1W   30 KT  35 MPH
 48H  05/0000Z 29.4N  34.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  05/1200Z 29.8N  35.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  06/0000Z 30.2N  35.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  07/0000Z...DISSIPATED

Forecaster Bucci

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