A low pressure system formed over South Texas on Monday evening. The low pressure system was designated as Invest 90L by the U.S. National Weather Service. At 2:00 a.m. EDT on Tuesday the center of a low pressure system was located at latitude 26.9°N and longitude 99.3°W which put the center about 35 miles (55 km) south-southeast of Laredo, Texas. The low pressure system was moving toward the northeast at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 25 m.p.h. (35 km/h) and there were wind gusts to 35 m.p.h. (55 km/h). The minimum surface pressure was 1009 mb.
An upper level low interacting with the northern end of a tropical wave caused a surface low pressure system to form over South Texas on Monday evening. The low pressure system was evident on surface weather maps which showed a weak counterclockwise rotation over southern Texas. Thunderstorms were occurring in bands in the eastern side of the low pressure system. Bands in the western and southern parts of the low pressure system consisted primarily of showers and lower clouds.
The low pressure system will move around the northwestern side of a high pressure system that extends from the western Atlantic Ocean to over the Gulf of Mexico. The high pressure system will steer the low pressure system toward the northeast during the next 24 hours. On its anticipated track, the low pressure system could move over the northwestern Gulf of Mexico.
If the low pressure system moves over the northwestern Gulf of Mexico, it will move into an environment that will be marginally favorable for the development of a tropical storm. The low pressure system will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level trough that is over the eastern U.S. The upper level trough will produce westerly winds that will blow toward the top of the low pressure system. Those winds will cause moderate vertical wind shear. The vertical wind shear will inhibit development, but the wind shear may not be enough to prevent the formation of a tropical depression or a tropical storm.
The U.S. National Hurricane Center is indicating that the probability is 60% that a tropical storm forms over the northwestern Gulf of Mexico. Reconnaissance planes have been tentatively tasked to fly into the the low pressure system on Tuesday night and Wednesday, if necessary.
The low pressure system has already dropped heavy rain over parts of South Texas and northern Mexico.
Flood Watches are in effect for South Texas, southeast Texas, most of Louisiana, and southern Mississippi.