A tropical disturbance currently designated as Invest 94L is likely to develop into a tropical cyclone east of the Lesser Antilles. The National Hurricane Center’s probability of formation of a tropical cyclone from this system during the next five days is 70%. At 2:00 p.m. EDT on Monday the center of Invest 94L was located at latitude 8.7°N and longitude 32.7°W which put it about 1830 miles (2950 km) east of the Lesser Antilles. It was moving toward the west at 4 m.p.h. (6 km/h). 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 1011 mb.
Invest 94L consists of a broad area of low pressure, but it has not developed a well organized inner core. The initial area of low pressure consisted of a counterclockwise rotation associated with a tropical wave that moved over the eastern Atlantic Ocean. The initial low slowed down as it was moving westward and a second tropical wave caught up to it. The thunderstorms from the two waves appear to be merging into a single system. An area of showers and thunderstorms on the northern and western sides of the surface low was part of the first tropical wave. Other bands of showers and thunderstorms south and east of the low are associated with the second tropical wave. If the broad low pressure system can collect the rotation from the two tropical waves, it could strengthen the surface low.
Invest 94L will move through an environment that will be favorable for the development of a tropical cyclone. It will move over water where the Sea Surface Temperature (SST) is near 28°C. There are easterly winds blowing at multiple levels in the atmosphere and there is little vertical winds shear. The existence of a surface low pressure system, warm SSTs and little vertical wind shear are the primary ingredients for the development of a tropical cyclone. That is the reason why there is strong probability that Invest 94L will develop into a tropical depression or a tropical storm.
Invest 94L will be steered by the subtropical high pressure system over the Atlantic Ocean. A general westerly or west-northwesterly track is forecast during the next few days. There is still significant uncertainty about the ultimate track and intensity of this system beyond that time frame. It will need to be monitored closely as it moves west.
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.
A tropical disturbance designated as Invest 94L moved out over the southern Bay of Campeche on Saturday morning. At 2:00 p.m. EDT on Saturday the center of Invest 94L was located at latitude 19.0°N and longitude 91.8°W which put it about 20 miles (35 km) northeast of Ciudad del Carmen, Mexico. Invest 94L was moving toward the west-northwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h). The minimum surface pressure was 1010 mb. The National Hurricane Center is putting the probability of development of a tropical cyclone at 50%. A reconnaissance plane has tentatively been tasked to investigate the system on Sunday afternoon, if necessary.
There is a broad area of lower pressure centered over the extreme southern Bay of Campeche. However, there is no well formed core at the center of the circulation. In addition there are only thin fragmented lines of showers and thunderstorms instead of well formed spiral bands. The circulation seems to exist primarily in the lower portion of the atmosphere. An upper level ridge east of Invest 94L is providing some upper level divergence.
The center of Invest 94L has moved over water and the Sea Surface Temperatures in the southern Bay of Campeche are 30°C – 31°C. So there is plenty of energy in the upper ocean to support tropical development. However, the western side of the upper level ridge is causing southerly winds to blow over the top of Invest 94L which is creating vertical wind shear. The southern portion of the circulation is still over land, which is also an inhibiting factor. The combination of positive and negative environmental factors are contributing to the uncertainty over the possible development of Invest 94L.
Invest 94L is being steered toward the west-northwest by a ridge of high pressure to its northeast. On its anticipated track, the center of Invest 94L will remain over water for another 24 to 48 hours. That time period represents the window during which Invest 94L could develop into a tropical depression or a tropical storm. Invest 94L is likely to reach the coast of Mexico in about two days and when it moves inland, the chance for development will end.