Tropical Storm Rina Forecast Discussion Number 4

By | September 29, 2023

WTNT43 KNHC 290840

Tropical Storm Rina Discussion Number   4
NWS National Hurricane Center Miami FL       AL182023
500 AM AST Fri Sep 29 2023

Rina has become slightly better organized overnight.  Deep,
persistent convection, with cloud top temperatures less than -80
degrees C, has mostly obscured the low-level circulation.  While the
subjective satellite intensity estimates have risen this cycle to
45-55 kt, the objective estimates have generally held steady around
35 kt.  The initial intensity is set to 40 kt to represent a blend
of these estimates.

The intensity forecast is still unusually complex and therefore, 
unclear.  While Rina appears to be gradually strengthening, most 
models agree that Philippe, the tropical storm to its west, will 
become the stronger storm.  As Philippe becomes better organized, 
Rina is expected to be sheared and subsequently weaken.  By days 4 
and 5, as Rina potentially moves away from the influence of 
Philippe, the GFS and ECMWF do not show the environmental conditions 
becoming any more conducive and continue to weaken Rina into a 
remnant low.  Only minor adjustments have been made to the latest 
intensity forecast.

Rina's motion is estimated to be north-northwestward, or 340/4 kt. 
The storm is expected to move generally west-northwestward to 
northwestward through day 3.  This is in part due to a binary 
interaction with Philippe and a mid-level ridge over the eastern 
subtropical Atlantic.  Later in the forecast period, Rina is 
forecast to turn north-northwestward to northward in the flow 
between the subtropical ridge and an upper-level trough over the 
western Atlantic.  There is still a large spread in the model 
solutions and thus, higher uncertainty in the track forecast, for 
the latter part of the forecast period.  The model guidance 
envelope has generally shifted eastward this advisory cycle, and 
the latest NHC track forecast has been nudged in this direction.  
The official track forecast lies between the previous prediction and 
consensus aids, TVCN and HCCA.


INIT  29/0900Z 18.9N  46.6W   40 KT  45 MPH
 12H  29/1800Z 19.3N  47.1W   45 KT  50 MPH
 24H  30/0600Z 19.8N  48.1W   45 KT  50 MPH
 36H  30/1800Z 20.4N  49.6W   45 KT  50 MPH
 48H  01/0600Z 21.1N  51.0W   40 KT  45 MPH
 60H  01/1800Z 22.0N  52.8W   35 KT  40 MPH
 72H  02/0600Z 23.3N  54.3W   35 KT  40 MPH
 96H  03/0600Z 26.0N  56.0W   30 KT  35 MPH
120H  04/0600Z 28.1N  55.6W   30 KT  35 MPH

Forecaster Bucci

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