Tropical Depression 18-E which formed earlier today has intensified into Tropical Storm Rachel.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Rachel was located at latitude 15.3°N and longitude 107.4°W which put it about 325 miles southwest of Manzanillo, Mexico and about 550 miles south-southeast of the southern tip of Baja California.  Rachel was moving toward the west at 12 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and the minimum surface pressure was 1004 mb.

A strong upper level ridge over northern Mexico has been producing northeasterly winds and wind shear over the circulation of Rachel.  The wind shear has been the reason why most of the thunderstorms have been located west of the center of circulation.  The northeasterly winds diminished slightly during recent hours and more thunderstorms developed closer to the center.  The improved organization allowed the wind speed at the surface to increase and Rachel became a tropical storm.  The upper level winds could decrease further and some additional intensification is possible.

A ridge in the middle levels is likely to steer Rachel to the west-northwest during the next day or two.  As Rachel moves farther north, it could be affected by a mid-level trough (i.e. a shortwave trough) in the westerly flow in about 72 hours.  If Rachel is strong enough and tall enough, then the mid-level trough could turn Rachel back to the northeast, which could move it toward Baja California.  If Rachel is weaker and the circulation does not extend as high into the atmosphere, then the mid-level trough may not affect the movement of Rachel.  In that case, it would probably continue to move west and dissipate over cooler Sea Surface Temperatures.