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Tropical Storm Hilary Discussion Number  30
NWS National Hurricane Center Miami FL       EP092017
200 PM PDT Fri Jul 28 2017
 
The satellite presentation of Hilary has improved this afternoon.
In experimental GOES-16 1-minute imagery, hints of a dimple near
the center of the convection even appeared at one point this
afternoon.  That said, current intensity estimates from TAFB and
SAB are now 55 kt, so the initial intensity has been held at that
value.  No change has been made to the intensity forecast, and
gradual weakening is still expected while Hilary moves over
progressively cooler water and into a more stable environment.
 
The main forecast problem is the track, marked by very little
run-to-run consistency among the models.  Conceptually, the
thinking hasn't changed since Hilary should be steered generally
northwestward for a day or two by the subtropical ridge before
interacting with Irwin. The details of that interaction vary greatly
from model-to-model and even run-to-run of a given model.  The final
tracker position of Hilary in the ECMWF and UKMET has shifted
approximately 200 and 400 n mi, respectively, since the last cycle.
On the other hand, the GFS depicts Hilary merging with Irwin in
about 72 h, over 500 nm south of the its previous 5-day point.
Despite the shifts in the models, the simple and corrected consensus
aids haven't shifted significantly.  The new official forecast has
been shifted about a degree to the northeast.  This is closer to,
but still southwest, of TVCN and HCCA, and is close to a average of
the GFS, ECMWF, and UKMET models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/2100Z 19.7N 119.2W   55 KT  65 MPH
 12H  29/0600Z 20.4N 120.4W   50 KT  60 MPH
 24H  29/1800Z 21.5N 122.2W   45 KT  50 MPH
 36H  30/0600Z 22.7N 124.2W   40 KT  45 MPH
 48H  30/1800Z 24.1N 126.5W   35 KT  40 MPH
 72H  31/1800Z 25.5N 130.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  01/1800Z 26.4N 132.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  02/1800Z 27.5N 134.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Zelinsky
 
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