Tropical Storm GENEVIEVE

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TROPICAL STORM GENEVIEVE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072014
800 PM PDT FRI JUL 25 2014

Genevieve has a ragged appearance in satellite imagery this
evening.  The central convection has diminished somewhat over the
past few hours, and it is displaced to the east of the low-level
center by 20-25 kt of westerly vertical wind shear.  The initial
intensity of 40 kt is based on earlier scatterometer data, along
with 35 kt satellite intensity estimates from TAFB and SAB.  The
wind radii have been revised based on the scatterometer data.

The initial motion is a possibly generous 270/4, as the center has
not moved much since the last advisory.  A mid/upper-level trough
north of the cyclone has broken the subtropical ridge and left
Genevieve in an area of light steering currents.  The global models
forecast the trough to move northeastward and weaken, allowing the
subtropical ridge to re-develop north of Genevieve.  The track
guidance is showing a little more spread than 6 hours ago, as the
18Z GFS is showing a more northerly motion than its previous run.
However, the center of the guidance envelope is essentially
unchanged from the previous advisory, and the new forecast track is
close to the previous track.  The new track is also near the various
consensus models.

The intensity forecast has become a little more puzzling.  The
global models now forecast the current shear to diminish during the
next 24-36 hours, and by the end of the forecast period Genevieve
could be in an area of light northeasterly shear. However, the SHIPS
and LGEM models do not respond much to the more favorable
environment and generally call for the cyclone to gradually weaken.
The GFDL and HWRF models forecast a stronger storm than the SHIPS
and LGEM, and the new GFS also shows a stronger cyclone than its
previous run. Given the divergent guidance, and the possibility that
the current shear could destroy the storm before it diminishes, the
new intensity forecast will change only slightly from the previous
forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  26/0300Z 12.2N 136.1W   40 KT  45 MPH
 12H  26/1200Z 12.3N 136.9W   40 KT  45 MPH
 24H  27/0000Z 12.5N 138.1W   40 KT  45 MPH
 36H  27/1200Z 12.8N 139.6W   35 KT  40 MPH
 48H  28/0000Z 13.1N 141.1W   35 KT  40 MPH
 72H  29/0000Z 13.5N 145.0W   30 KT  35 MPH
 96H  30/0000Z 14.0N 148.0W   30 KT  35 MPH
120H  31/0000Z 14.0N 151.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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