Bill Makes Landfall in Texas; Greatest Impact Still to Come

Less than 12 hours after it was named, Tropical Storm Bill pushed ashore near Matagorda Bay, Texas, at 11:45 am CDT Tuesday. Peak winds at landfall were 60 mph, with a gust to 53 mph reported at both Palacios and Port O’Connor, Texas. Some minor coastal flooding was observed, with the water level at Port Lavaca about 3 feet above normal, but on the whole Bill caused relatively little trouble along the Texas shore. That may not be the case inland over the next couple of days, as Bill churns slowly north and its showers and thunderstorms continue to organize.


Figure 1. GOES satellite image of Tropical Storm Bill as it neared the Texas coast. Image credit: NASA/GOES Project Science.


Figure 2. Bill’s thunderstorm activity continued to organize on Tuesday evening even with the center now inland. This NWS radar image from the WU Storm app is from 7:20 pm Tuesday, June 16.


At 7:00 pm CDT Tuesday, Bill was located about 10 miles northeast of Victoria, TX, with a central pressure of 999 mb and peak sustained winds of 45 mph. Bill wobbled westward this afternoon, but it was moving north-northwest at 9 mph as of 7 pm Tuesday. An observer in northwest Houston reported 0.92” of rain in just 15 minutes on Tuesday afternoon. Even as the storm weakens to a depression by Wednesday morning, Bill should maintain its identity as a distinct surface low. Multiple models are suggesting that Bill could even reorganize somewhat over northeast Texas or southeast Oklahoma late Wednesday or early Thursday. This uncommon occurrence is being made possible by extremely wet soils over much of Texas and Oklahoma, which just saw the wettest month in their history. As discussed in our post Monday, there’s an increasing amount of research on the process by which a tropical cyclone can re-intensify well inland if soils are sufficiently moist--what’s been called the “brown ocean effect.”


Figure 3. Projected three-day precipitation totals from the NOAA Weather Prediction Center, for the period from 0000 GMT June 17 to June 20, show the expected track of Bill around the high-pressure center in the southeast U.S. Image credit: NWS/WPC.

Heavy rain threat still on tap
Bill’s track inland was just far enough west of Houston that the metro area was largely spared from heavy rain on Tuesday afternoon. Convection may organize somewhat tonight, as the surface layer decouples from the rest of Bill, and there is likely to be a core of intense rainfall somewhere near the I-35 and I-45 corridors of central Texas on Wednesday. The Dallas-Fort Worth area will be in Bill’s crosshairs by Wednesday afternoon and evening, with the local NWS office warning of a risk of widespread 3 - 6” rains and local amounts of 6” - 12” near Bill’s center and where persistent banding occurs. Tornadoes are also quite possible tonight and Tuesday, especially northeast of Bill’s center; a long-lived tornado watch is in effect for much of southeast Texas through midnight CDT Tuesday night. With soils saturated, the risk of flash flooding is serious, particularly over north-central and northeast Texas late Wednesday and over roughly the southeast half of Oklahoma from late Wednesday into Thursday. Rivers and reservoirs still engorged from Texas and Oklahoma east to Arkansas and Louisiana will not be able to handle much additional rain from Bill, so flooding may be a continued headache for days to come. Shreveport, LA, has already seen extensive damage from some of the highest levels since 1945 along the Red River.

As Bill moves north, its moisture will intersect a weak surface front that arcs from central Oklahoma into the Ohio Valley, and bands of heavy rain may develop well north of the actual circulation. Flash flood watches were in effect on Tuesday night all the way from south Texas to central Illinois.


Figure 4. Rainfall in Mexico from Hurricane Carlos and Tropical Storm Bill for the 24 hours ending at 8 am Tuesday June 16, 2015. The maximum rainfall amount was 4.15" (105.5 mm) at Pajaritos; just under 4" fell near Puerto Vallarta. Image credit: CONAGUA.

Hurricane Carlos proving difficult to predict
An Air Force hurricane hunter aircraft found that Hurricane Carlos was stronger than expected on Tuesday afternoon, with top winds near 90 mph. Maximum sustained winds were reported at 85 mph in the 7:00 pm CDT advisory. Carlos continues its slow northwest motion at 5 mph, almost parallel to and about 80 miles offshore from the coast. Fortunately, Carlos is a very small storm, with tropical storm-force winds that only extend outwards about 45 miles. So far its heavy rains have mostly stayed offshore, though a few mountainous areas to its north received about 4" of rain in the 24 hour period ending at 8 am Tuesday. Satellite loops showed an intermittent eye today, with the hurricane's heavy thunderstorms remaining just offshore from the coast near Manzanillo, Mexico. Dry air and a more stable atmosphere should lead to weakening on Wednesday, but this forecast is low-confidence. The storm's small size has made it difficult to predict for the computer models, and Carlos may be able to maintain hurricane strength longer than expected. Carlos will likely bring heavy rains of 3 - 6 inches to portions of the Southwest Mexican coast through Thursday, which will cause flash flooding and mudslides.


We’ll be back with an update on Wednesday morning.

Bob Henson (Bill), Jeff Masters (Carlos)