Heavy Rainfall and Possible Tropical Development Briefing 12:00 PM CDT Wednesday, September 12, 2018 Prepared by: Barry Goldsmith NWSBrownsville weather.gov/rgv Skinny Brownsville/RGV WEATHER FORECAST OFFICE Visible Satellite, 2 PM June 19 • Atmospheric “river” of deepest moisture (green arrow) remains over western Gulf and Texas coast, close enough to concern Lower RGV communities late Wednesday- Wednesday evening (inset; east of “x”) • Plenty of low level moisture/instability for scattered showers/heavier thunderstorms through Thursday • Tropical disturbance (red circle) became disorganized overnight, but probability still at 70% of becoming a cyclone (depression) on Thursday • Focus remains on additional heavy rainfall • Additional Falcon Reservoir relief is expected from both recent rains as x well as the future moisture from the disturbance over the weekend and beyond 9/12/2018 2:00 PM weather.gov/rgv Story So Far Brownsville/RGV WEATHER FORECAST OFFICE Rainfall Since Sept. 8th (overnight) through Sept. 12th (AM) 4-8 3-6 inches inches 6-12 inches 6-12 Houston inches Houston Corpus Corpus 6-10 Brownsville1-3+ Brownsville inches inches 4-7 5-7 inches inches 9/12/2018 2:00 PM weather.gov/rgv Brownsville/RGV WEATHER FORECAST OFFICE Brooks/Hidalgo: Organized bands not expected, but any additional rains a potential flood threat due to oversaturated soil Locally 2-3” in stronger cells along/east of US 77 late afternoon-late evening 9/12/2018 2:00 PM weather.gov/rgv Tropical Outlook Brownsville/RGV WEATHER FORECAST OFFICE As of 1 PM September 11, 2018 • Order of Concerns: – Heavy Rainfall/Flooding – Rip Currents and Tidal Run Up to Dunes – Gusty Winds (in squalls but nothing out of ordinary for region) • Timing of Impacts: Thursday Night through Friday Night (through Saturday for Flooding) • Development could mean just a depression; wind shear from recent storms playing a role in slow growth • “Lean” for heaviest rainfall to favor the coastal bend through South Texas Brush Country/RG Plains 9/12/2018 2:00 PM weather.gov/rgv Forecast Rainfall Thru 7 PM Sep. 15 Brownsville/RGV WEATHER FORECAST OFFICE These are averages. Higher amounts likely in organized bands Note: Locally Higher Amounts possible, up to 5+ inches, in organized cells or bands 9/12/2018 2:00 PM weather.gov/rgv Rio Grande and Streams Rising Brownsville/RGV WEATHER FORECAST OFFICE From 6-12+ inches in central Hidalgo flowing “downhill” . Arroyo Colorado (top left) at Harlingen, Los Olmos Creek (Falfurrias) running high; low water bridges flooded . Rio Grande at San Benito expected to spike and could run higher than forecast if more heavy rain falls over Hidalgo/Cameron . Additional flood “waves” possible over weekend north of Laredo, could create wider river and threaten USBP equipment north of Falcon Reservoir 9/12/2018 2:00 PM weather.gov/rgv Falcon Reservoir Relief Brownsville/RGV WEATHER FORECAST OFFICE Pool Level rises continue…more coming Note: Falcon pool capacity is likely to rise above 50% Texas Share in one to two weeks 9/12/2018 2:00 PM weather.gov/rgv Coastal Hazards Brownsville/RGV WEATHER FORECAST OFFICE . Tide levels could reach the dune line at high tide Thursday and Friday night . SPI High tides at 757 PM Thursday Sept. 13 and 937 PM Friday Sept. 14 . Surf waves could build to 4 to 5 feet, locally 6 feet Friday and continue Saturday before receding . Dangerous rip currents arrive Thursday and continue through Saturday Photo: September 2013 9/12/2018 2:00 PM weather.gov/rgv Potential Impacts Brownsville/RGV WEATHER FORECAST OFFICE . Flooding (2 to 3 feet water depth) is possible in poor drainage locations of populated lower Valley (Brownsville/Harlingen/Raymondville toward coast) late Wednesday-Wednesday evening . Hidalgo and Brooks Co. are saturated. Localized 2-3” deluges on top of areas that received 6-12+ inches will cause repeat flooding. These rains could happen at any time Thursday afternoon, and Friday- Saturday. Dangerous rip currents will begin Thursday and continue through Saturday. Tides may run up to the dune line or just inside the dunes at high tide Thursday and Friday night. 9/12/2018 2:00 PM weather.gov/rgv.