[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 290248
TCDAT3

Tropical Storm Rina Discussion Number   3
NWS National Hurricane Center Miami FL       AL182023
1100 PM AST Thu Sep 28 2023

The future for Rina has not become any clearer during the past
several hours. The cyclone is more or less unchanged since the last
advisory, with its center still generally exposed to the northwest
of the associated deep convection. The intensity remains 35 kt based
on recent operational SAB, TAFB, and UW-CIMSS ADT estimates.

During the past day or so, the guidance has flip-flopped over
whether Rina or nearby Tropical Storm Philippe will become dominant.
While Rina appears to be the better organized of the two at the
moment, the latest runs of most models indicate that Philippe is
more likely to become the dominant cyclone by early next week. Until
the forecast becomes more consistent, it appears prudent to make
only very small incremental changes to the official NHC forecast.
Therefore, both the intensity and track forecasts are very similar
to the previous advisory, but confidence in the NHC forecast is
unusually low.

Rina is heading northwestward into an area of stronger expected
vertical wind shear. A combination of the circulation of Philippe
and a ridge centered over the eastern subtropical Atlantic should
keep Rina generally on a west-northwest to northwest heading for at
least a few days. After that, if Rina deepens or at least maintains
its current strength and structure, it could begin to lift
northward. However, if it weakens, Rina or its remnants will likely
turn westward by early next week. The wind shear should prevent Rina
from strengthening much, and could eventually lead to its
dissipation in as soon as 4 or 5 days. The NHC track forecast is
based heavily on a blend of the previous NHC forecast with the ECMWF
and GFS ensemble means, while the intensity forecast is close to the
IVCN consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 18.4N  46.6W   35 KT  40 MPH
 12H  29/1200Z 19.1N  47.3W   40 KT  45 MPH
 24H  30/0000Z 19.6N  48.3W   45 KT  50 MPH
 36H  30/1200Z 19.9N  49.4W   45 KT  50 MPH
 48H  01/0000Z 20.4N  50.7W   40 KT  45 MPH
 60H  01/1200Z 21.0N  52.4W   35 KT  40 MPH
 72H  02/0000Z 22.0N  54.1W   35 KT  40 MPH
 96H  03/0000Z 24.5N  57.0W   30 KT  35 MPH
120H  04/0000Z 27.0N  57.0W   30 KT  35 MPH

$$
Forecaster D. Zelinsky
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