Heavy rainfall is likely for southern and coastal Texas and parts of coastal Louisiana through at least mid-week. A tropical wave and upper-level low will work in tandem to aid in tropical moisture streaming into the region as well as provide the lift to generate convection. At this hour, convection is moving into coastal Texas and coastal Louisiana from the Gulf of Mexico. This will continue throughout the day and coverage should increase once the convective temperature is met. At the same time, rainfall rates will increase and may exceed 1″ per hour. As the upper-level low moves closer to the Texas coast by mid-week, convection will convection will continue to move into the region from the Gulf as energy rotates around the low, and convection will move further inland into Texas.
Widespread rain totals of 3-5″ will occur cross coastal Texas with areas receiving 5-10″ from Corpus Christi to Beaumont–this includes Houston (isolated areas may see 10-15″ of rainfall). Western coastal Louisiana will see 2-4″. These rainfall amounts will lead to areas of flooding. This is especially true where training occurs since these tropical rainbands will produce 1-2″ per hour rainfall rates at times. At this time, there are no Flash Flood Watches in place, but with the heaviest rainfall expected on Tuesday and Wednesday, it is possible Flash Flood Watches will be issued later today. If you live in this area, please remain alert.
Remember: turn around don’t drown! Here is the latest precipitation map from the National Weather Service.
Tropical moisture is still expected to cause heavy rainfall across much of southern Texas and western Louisiana this weekend through early next week. The increase in moisture is due to a tropical wave in the southern Gulf of Mexico. This wave is being monitored by the National Hurricane Center (NHC) and has a 10% chance of development over the next few days (see Fig. 1). The reasoning behind there only being a 10% chance of development into a tropical cyclone is because environmental conditions are not particularly favorable for cyclogenesis and low support from numerical guidance. Wind shear has been high in the Caribbean and dry air flowing down from Mexico have hindered development. With that said, the wave is moving into an environment that is slightly more favorable for development. Environmental wind shear is more relaxed in the Gulf (see Fig. 2) and there is increased surface convergence (see Fig. 3). This has led to a flareup of convection (see Fig. 4) associated with the wave this morning. It is possible that development percentages will be slightly increased this afternoon by the NHC.
Fig. 1: NHC Forecast Graphic
Fig. 2: University of Wisconsin Wind Shear Map
Fig. 3: University of Wisconsin Surface Convergence Map
Fig. 4: Morning IR Imagery
Regardless of development into a tropical cyclone, this wave will slowly move towards the Texas Coast over the next 48 hours, increasing moisture. Isolated to scattered convection will begin to impact coastal areas of the western Gulf today with more widespread and heavier rainfall impacting this region Sunday through Tuesday. Widespread rainfall totals of 1-3″ are likely across southern Texas and southern Louisiana with 3-6″+ amounts possible for coastal Texas and southwestern Louisiana (see Fig 5). Cities that will likely see impacts from heavy rainfall are: Galveston, TX; Houston, TX; Austin, TX; San Antonio, TX; Brownsville, TX; Lake Charles, LA and Lafayette, LA.
Fig. 5: WPC Precipitation Forecast Through 7-Days
Other impacts in this region are gusty winds with thunderstorms, cloud-to-ground lightning, and coastal flooding from prolonged on-shore flow. The moisture associated with this system may move eastward by mid-week towards parts of the Mid-West potentially increasing rain chances for this region and areas east of the Mississippi beyond this timeframe. There is also the possibility this wave may stall in southern Texas/northern Mexico. These details will be ironed out with time.
Please remember to turn around don’t drown!
Gulf Coast Tropical Moisture
Tropical moisture is expected to move into Texas and Louisiana this weekend and next week. A large area of thunderstorms is located across the western Caribbean. This area of thunderstorms will move over the Yucatan Peninsula into the southern Gulf over the next 24 hours. At this hour, the National Hurricane Center (NHC) is keeping a close eye on this tropical wave and currently is giving it a 20% of tropical cyclone development over the next 5 days (see Fig. 1). The main hinderance are the strong upper-level winds.
Fig. 1: NHC Area Being Monitored For Tropical Development
Even if the area of thunderstorms does not develop further, heavy rainfall is likely for parts of Texas and Louisiana from Saturday through Monday. This includes some major cities, which include: Houston, San Antonio, Austin, and New Orleans. Widespread 2-4″ is possible across the northwestern Gulf States with isolated amounts greatly exceeding this (see Fig. 2).
Fig. 2: WPC Precipitation Forecast Through 7 Days
Southwest Tropical Moisture
The Southwest can expect tropical moisture, too, but from a different system. Tropical Storm Bud is moving northward off of the coast of Mexico at this hour. Bud is weakening as it moves northward but is expected to bring heavy rainfall to parts of western Mexico, eastern parts of the Baja of California, and Southwest parts of the United States as it moves into the Gulf of California and eventually into northern Mexico (see Fig. 3). This rainfall moving into the Southwest (Arizona, New Mexico, and southern Colorado) will likely create flash flooding in localized areas. Rain chances increase by Thursday with the best chances Friday night into Saturday. Widespread 0.75-1.50″ are likely with isolated 2-4″ amounts (see Fig. 4). Dangerous flash flooding looks likely in areas that have terrain in southern Colorado, eastern Arizona, and central and western New Mexico.
Along with flash flooding, cloud-to-ground lighting is possible, along with the potential for microbursts during the afternoon hours where strong heating occurs. High temperatures will be well below normal over the weekend (see Fig. 5). A trough will dig into the West, which should move the remnants of Bud eastward by early next week but isolated rain chances look to continue in this region due to the trough.
Fig. 3: NHC Bud Forecast Track
Fig. 4: WPC Precipitation Forecast Through 7 Days
Fig. 5: Saturday and Sunday High Temperature Anomalies