Tropical Depression 01E formed southwest of Baja California on Thursday afternoon. A distinct low level center of circulation formed inside a larger area of low pressure that was previously designated as Invest 90E. The National Hurricane Center (NHC) determined that the system possessed sufficient organization and NHC designated it as Tropical Depression 01E. At 5:00 p.m. EDT on Thursday the center of Tropical Depression 01E was located at latitude 12.4°N and longitude 126.5°W which put it about 1310 miles (2105 km) west-southwest of the southern tip of Baja California. Tropical Depression 01E was moving toward the west-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1007 mb.
Tropical Depression 01E formed in a larger area of low pressure that was moving slowly westward over the Eastern North Pacific Ocean. More thunderstorms formed near the center of the low pressure system and a distinct low level center became apparent on visible satellite images. An upper level trough located west of the depression was producing southwesterly winds which are blowing toward the top of the circulation. Those winds were causing moderate vertical wind shear and the shear was limiting the development of thunderstorms in the western half of the depression. Most of the stronger thunderstorms were occurring east of the center of circulation. The bands in the western half of the depression consisted mostly of lower clouds and showers. Storms east of the center were producing some upper level divergence which was pumping mass away to the east of the depression.
Tropical Depression 01E will move through an environment only marginally favorable for intensification. It will move over water where the Sea Surface Temperature is near 27°C. So, there is enough energy in the upper ocean to support intensification. However, the upper level trough will continue to produce moderate vertical wind shear. The upper level winds could be strong enough to prevent further intensification. If the upper level winds slow, then there is a chance the depression could strengthen into a tropical storm during the next day or two.
Tropical Depression 01E is moving south of a subtropical ridge which is steering the depression toward the west-northwest. The subtropical ridge is forecast to steer the depression in a general westerly direction during the next several days. On its anticipated track Tropical Depression 01E poses no immediate threat to any land areas.
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.
May 15 is the official start of the hurricane season for the Eastern North Pacific Ocean. The Sea Surface Temperatures (SSTs) should be cooler than they were in 2015, since the El Niño is dissipating. That could produce a hurricane season in which the activity is nearer to normal. In a normal year we might expect 13-17 named storms, 7-10 hurricanes and 3-4 major hurricanes. Of course, other environmental factors including the location and strength of atmospheric systems will also determine how active the season is.
The National Hurricane Center (NHC) is currently monitoring Invest 90E which is about 950 miles (1530 km) south-southwest of the southern tip of Baja California. There is a well defined low level circulation in Invest 90E, but there are no deep thunderstorms. NHC is giving Invest 90E a 20 percent chance of developing into a tropical cyclone during the next five days.