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Tropical Storm Rina Discussion Number  12
NWS National Hurricane Center Miami FL       AL192017
1100 PM AST Wed Nov 08 2017

A small area of deep convection persists near the center of Rina,
likely supported by very cold temperatures aloft and increasing
upper-level divergence overcoming SSTs less than 20C. The initial
intensity remains 45 kt based largely on continuity from the ASCAT
pass earlier today, as the latest ASCAT passes missed much of Rina's
circulation. Given the maintenance of deep convection, Rina remains
a tropical cyclone, but should not be one for long as vertical
shear is expected to increase above 30 kt and SSTs cool below 15C
along the forecast track in the next 12 hours. The cyclone should
become post-tropical by 12 hours and merge with a frontal zone by 24
hours. Post-tropical Rina should open up into a trough in 36 to 48
hours in the fast westerly flow over the north Atlantic. No change
in strength is forecast prior to dissipation, based on global model
guidance.

Satellite fixes indicate that Rina moved a little to the west of the
previous forecast track in the past few hours, but the cyclone now
appears to be moving north-northeastward or 020/20. The cyclone is
forecast to accelerate northeastward over the next 24 hours as it
becomes embedded in the mid-latitude flow, and an even faster east-
northeastward motion is expected on Friday prior to dissipation. The
new NHC track forecast has been adjusted to the left and is closer
to the ECMWF model in the short range, since that model has best
handled the recent motion of Rina. At 24 to 36 hours, the NHC
forecast lies to the left of the latest multi-model consensus aids.

The track, intensity and structure forecasts of Rina during its
post-tropical phase have been coordinated with the NOAA Ocean
Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 42.5N  48.3W   45 KT  50 MPH
 12H  09/1200Z 45.7N  46.5W   45 KT  50 MPH...POST-TROPICAL
 24H  10/0000Z 51.0N  40.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 36H  10/1200Z 55.0N  26.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  11/0000Z...DISSIPATED

$$
Forecaster Brennan

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