000
WTNT42 KNHC 062041
TCDAT2

TROPICAL STORM GRACE DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072015
500 PM AST SUN SEP 06 2015

Grace is a fairly well-organized, compact tropical cyclone with
banding features and well-defined upper-level outflow to the north
and south of the system.  Deep convection has been rather limited
today, but recent imagery shows some cold cloud tops developing near
the center. The current intensity is set to 45 kt in agreement with
a subjective Dvorak estimate from TAFB. Since the vertical wind
shear is expected to remain modest for the next 24 hours or so,
there is window of opportunity for short-term strengthening.  Within
36 hours, the dynamical guidance shows the shear increasing to over
20 kt, and this should cause a weakening trend beginning around that
time.  The official intensity forecast is a little above the model
consensus for the first half of the period and close to, or a little
below, the consensus thereafter. It is worth noting that the GFS
shows significant weakening of the cyclone in 4 to 5 days, with the
ECMWF showing dissipation by that time.

The storm has accelerated a bit and is now moving at about 280/13.
For the next several days, Grace should continue to move within a
moderate low- to mid-level easterly flow on the south side of the
subtropical ridge.  The track guidance models are noticeably faster
than they were on the previous cycle, so the official forecast is
adjusted accordingly.  The NHC track is not far from the latest
dynamical model consensus, TVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 13.2N  31.2W   45 KT  50 MPH
 12H  07/0600Z 13.3N  33.3W   50 KT  60 MPH
 24H  07/1800Z 13.6N  36.2W   55 KT  65 MPH
 36H  08/0600Z 13.9N  39.1W   55 KT  65 MPH
 48H  08/1800Z 14.3N  42.1W   50 KT  60 MPH
 72H  09/1800Z 15.0N  48.5W   45 KT  50 MPH
 96H  10/1800Z 16.0N  55.0W   40 KT  45 MPH
120H  11/1800Z 17.0N  61.0W   30 KT  35 MPH

$$
Forecaster Pasch