WTPZ42 KNHC 260233
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