Possible Tropical Development South of El Salvador

A broad area of low pressure has formed over the Eastern North Pacific Ocean south of El Salvador.  The environment is favorable for the development of a tropical cyclone.  The National Hurricane Center (NHC) has designated the low pressure system as Invest 90E.  NHC is indicating that there is a 50% probability of the formation of a tropical depression during the next 48 hours and an 80% probability of formation during the next five days.

At 2:00 p.m. EDT on Monday the center of Invest 90E was located at latitude 7.9°N and longitude 89.5°W which put it about 370 miles (595 km) south of San Salvador, El Salvador.  Invest 90E was stationary.  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1008 mb.

More thunderstorms formed on Monday around a broad area of low pressure south of El Salvador.  Visible satellite imagery suggested a broad counterclockwise rotation of the area of thunderstorms, but there were no indications of a well developed core of the circulation.  Several smaller centers of rotation were visible within the broad low pressure system, but these may be transient features.  The broad area of thunderstorms was producing upper level divergence.  The divergence is pumping out mass and if that continues, then the surface pressure will decrease.

The area of low pressure is in an environment favorable for tropical development.  It is moving over water where the Sea Surface Temperature is near 30°C.  The low is sitting underneath an upper level ridge and the winds in the upper level are weak.  There is little vertical wind shear and there is nothing to inhibit upper level divergence.  The circulation should continue to organize, which is why the probability of formation of a tropical cyclone is high.

The area of low pressure is in an area where the steering currents are weak and Invest 90E was nearly stationary on Monday.  A high pressure system northeast of the broad area of low pressure system is expected to strengthen.  When that happens, the high is likely to steer the area of low pressure toward the northwest.