|Above: Tropical Storm Harvey, with its center inland near the Texas/Louisiana border, as seen by the GOES-16 satellite at 9:15 am CDT Wednesday, August 30, 2017. Image credit: NOAA/RAMMB. GOES-16 data are considered preliminary and non-operational.
After causing severe wind damage near its landfall point in Rockport, Texas on Saturday, followed by an almost unimaginable flood catastrophe Saturday through today in Houston, Harvey has notched yet another extreme rainfall catastrophe this morning, in the Golden Triangle area of Texas, encompassing the cites of Beaumont/Port Arthur/Orange (population 410,000). Harvey made its final landfall in Western Louisiana near the Texas border near 4 am CDT Wednesday, with top winds near 45 mph. Overnight, Harvey dumped a devastating deluge of rain over the region, where catastrophic rains in excess of five inches per hour fell early this morning.
|Figure 1. Lake Charles, Louisiana radar from 8:18 am CDT Wednesday, August 30, 2017, showing rainfall rates of up to 2.1” per hour affecting the Beaumont, Texas region.
At the Beaumont-Port Arthur Airport, 26.03” of rain fell on Tuesday, which is more than double Beaumont's previous calendar-day record of 12.76" on May 19, 1923, in records going back to 1901. Between 10 pm last night and 1 am this morning, 11.86” fell. So far on Wednesday, 4.71” has been reported (as of 11 am CDT), bringing their 5-day storm total rainfall to a staggering 47.98”. The intense rains caused extreme flash flooding that inundated all of Port Arthur, according to Mayor Freeman, who showed a video this morning of the inside of his flooded house on his Facebook page. Port Arthur is the site of the nation’s largest oil refinery, which was forced to shut down due to the floods. The nation’s second-largest refinery, in Baytown, TX, was also forced to shut down yesterday, due to flooding-induced roof damage. In all, at least 12 refineries are currently offline due to Harvey.
PLEASE PLEASE PLEASE send help to— kayla. (@kaykay_dadon) August 30, 2017
820 Smith Rd Port Arthur, Texas 77640. The water is rising and almost at the roof. Anyone ! Help! pic.twitter.com/a67csI7cMJ
The extreme rains turned I-10 near Beaumont, Texas into a wild river with breaking waves this morning, as seen in this remarkable video of a rescue boat plowing through the waters. Several rescue boats capsized in the raging waters, and citizen rescue boats were told to stand down and let only the Coast Guard handle rescues early this morning. The latest Weather.com write-up on the situation in Port Arthur detailed a flooded shelter, house fires, overwhelmed 911 operators, and a plea for rescue boats.
A small shift with big consequences
Multiple forecast models earlier this week had called for a final burst of 15” – 25” in rainfall around the Houston area from Tuesday into Wednesday. Instead, that burst took shape from just east of Houston to the TX/LA border, resulting in the catastrophic overnight flooding in the Golden Triangle. Lance Bosart (University at Albany, SUNY) notes that Harvey’s center “wobbled” during its arc southeastward from Texas into the Gulf and back northeastward to its landfall in Louisiana. In addition, radar data showed a secondary circulation—resembling a mesoscale convective vortex (MCV, or Mesovortex)—moving northeast across the Golden Triangle while the center of Harvey was spinning well offshore (see embedded tweet at the bottom). Although models successfully predicted the intense rain core 1 to 2 days in advance, its small eastward shift (less than 100 miles) had huge consequences for people in both the Houston and Golden Triangle areas.
|Figure 2. The NHC track for Harvey shows a wobble southeast of Houston. Image credit: NHC.
Harvey’s track over the last several days has carved out a loop around far southeast Texas, helping to keep heavy rains pinned in the Golden Triangle region on Tuesday night and into Wednesday morning. The Lake Charles, Louisiana radar showed that intense bands of rain with rainfall rates as high as 1.5” per hour continued to affect Beaumont, Port Arthur, and Orange late this morning, and the region can expect several more hours of heavy rains, with accumulations of another 2 - 4" possible before Harvey takes its rains to the north.
Heavy rains will spread northeast into the mid-Mississippi Valley as Harvey works its way northeast over the next three days. The NWS Weather Prediction Center has placed much of northwest Louisiana along Harvey’s path in a high risk for excessive rainfall. Torrential rains are also possible on Wednesday eastward along the front that lies from southern Louisiana to the Florida Panhandle, as Harvey pushes moisture northward atop the front. By Thursday, NHC projects Harvey to be a slowly weakening tropical depression in northeast Louisiana. It will likely be centered somewhere in western or central Tennessee by Friday, perhaps still at depression strength. Harvey should accelerate northeastward and become post-tropical by Saturday.
Rains of 4-6”, with pockets of up to 10”, will accompany Harvey on its trek inland as far north as western Kentucky, where interactions with the jet stream may boost totals somewhat. Thankfully, by this point Harvey will be moving quickly enough to prevent the massive rainfall totals observed in southeast Texas.
|Figure 3. Three-day rainfall forecast from 8:00 am CDT Wednesday, August 30, 2017, to 8:00 am Saturday, September 2. Image credit: NOAA/NWS/WPC.
We’ll have more on Harvey’s impact on Houston, where the rains have finally stopped. We'll dicuss the rain forecast for next week in Houston, and newly-formed Tropical Storm Irma in the far Eastern Atlantic later today.
Bob Henson co-wrote this post.