More thunderstorms developed near the center of a slow moving area of low pressure south of Mexico and the National Hurricane Center classified the system as Tropical Storm Vance.  At 5:00 p.m. EDT the center of Vance was located at latitude 11.0°N and longitude 101.0°W which put it about 415 miles south of Acapulco, Mexico.  Vance was moving toward the west at 5 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and the minimum surface pressure was 1005 mb.  Vance is the 20th named tropical cyclone for form over the Eastern North Pacific during 2014, which is the most since 1992.

Vance is being steered toward the west by an upper level ridge to its north.  Vance is expected to take a long, clockwise path as it moves around the western edge of the ridge.  Some recent guidance from numerical models suggests that Vance could move farther westward than was indicated in previous model forecasts.   Eventually, when Vance moves farther north, it is anticipated that it will be turned northeastward by a large trough off the west coast of North America.  The trough could pull Vance toward the west coast of Mexico sometime next week.

There are southwesterly winds blowing over the top of Vance in the upper levels and the result is that most of the thunderstorms are developing north and east of the center.  The shear is expected to decrease on Friday.  Vance will be moving over Sea Surface Temperatures (SSTs) that are warmer than 29°C.  So, there will be sufficient energy for intensification and some guidance is indicating that Vance could become a hurricane.   When the upper level trough begins to affect Vance, the wind shear will increase and it could be on a weakening trend when it turns toward the coast of Mexico next week.