An Air Force Reserve Hurricane Hunter aircraft investigated an area of low pressure over the Bay of Campeche on Sunday afternoon and found that there was sufficient organization for the National Hurricane Center to designate the system Tropical Depression 4.  At 11:00 p.m. EDT on Sunday the center of Tropical Depression 4 (TD4) was located at latitude 20.1°N and longitude 95.4°W which put it about 145 miles (230 km) east-southeast of Tuxpan, Mexico.  TD4 was moving toward the west at 7 m.p.h. (11 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. (70 km/h).  The minimum surface pressure was 1009 mb.  The government of Mexico has issued a Tropical Storm Warning for the portion of the coast from Laguna Verde to Rio Panuco.

Although the reconnaissance aircraft found that the circulation was better organized than it was on Saturday, it still is not well organized.  There is a distinct center of circulation, but the thunderstorms near the center have been developing and then weakening.  The circulation appears to be somewhat elongated and stretches from the southeast toward the northwest.  A persistent rain band is east and north of the center of circulation and some of the stronger winds are occurring in the rainband.  A new cluster of thunderstorms appears to be developing near the center, and it could represent an improvement in the organization of the depression.

The environment is marginally favorable for intensification.  Tropical Depression 4 is over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is producing some vertical wind shear, but the upper level ridge is also enhancing upper level divergence to the east of the depression.  The depression is close to tropical storm intensity and it has another 12-18 hours to intensify before it makes landfall in Mexico.

A ridge of high pressure that extends from the Atlantic Ocean over the Gulf of Mexico is steering the depression toward the west and that general steering motion is expected to continue.  On its anticipated track, Tropical Depression 4 will make landfall in Mexico on Monday.  The depression could produce locally heavy rainfall and flash flooding will be the primary risk when it makes landfall.