French Floods Kill 14; 94L Moves Inland; Tara Drenching Manzanillo

October 16, 2018, 2:51 PM EDT

Above: An aerial view shows a collapsed bridge in the city of Villegailhenc, near Carcassonne, southern France, on October 15, 2018, following heavy rains that saw rivers bursting banks. Flash floods swamped a number of towns and villages around the fortress city of Carcassonne, leaving a trail of overturned cars, damaged roads and collapsed homes. Image credit: Sylvain Thomas/AFP/Getty Images.

Fourteen people were killed in southwest France near the town of Carcassonne Monday morning, after torrential rains of over 9” in six hours caused devastating flash floods. According to meteorologist Etienne Kapikian of Meteo France, ex-hurricane Leslie's role in these floods were marginal, even though the remains of the hurricane lay just to the south. The dramatic flash-flooding came from a large trough of low pressure over France and Spain. East-southeast winds from the warm Mediterranean converged with light west-northwest winds along the axis of the trough near Carcassonne, feeding intense thunderstorm updrafts that led to very heavy rains. A local maximum of 11.63” (295.5 mm) was recorded in 12 hours in the village of Trèbes (a few km east/north-east from Carcassonne), with about 9.45” (240 mm) in 6 hours between midnight and 6 am local time. Most people were asleep then, making warnings difficult.

Ex-hurricane Leslie's remnants were embedded in the broad-scale trough to the south of the heavy rain region, and probably added some cyclonic spin to the southern tip of the trough over Spain. This helped to intensify the south-easterly moist Mediterranean flow over southern France, and may have added a bit of heat and moisture to the air. However, "the ingredients would have been favorable to a high precipitation event even without the existence of Leslie's remnants", Etienne told us in an email. So, Leslie's remnants may have indirectly added a bit to these intense rains, but we shouldn’t overplay Leslie's role. Here is a summary of this flash flood event by Meteo-France, including a map of radar-estimated rainfall amounts.

Texas flooding causes bridge collapse

A bridge collapsed Tuesday morning after heavy rain in south-central Texas, about 75 miles northwest of Austin, triggered major flooding. Evacuations and water rescues were underway in the region late Tuesday morning. A section of the FM 2900 bridge collapsed in Kingsland (population 3000) on Tuesday morning, sending chunks of the bridge down the Llano River. The Llano is now at its second highest crest on record and may threaten the record from 1935. As much as 10 inches of rain had fallen in western Llano County in the 30 hours ending Tuesday morning, according to weather.com.

94L moving inland over Belize without developing

A broad area of low pressure (94L) over the southwestern Caribbean near the northwest coast of Honduras was moving inland over Central America late Tuesday morning. Satellite images and Belize radar showed that 94L did not have an organized surface circulation, and the system has run out of time to develop into a tropical depression. Heavy rains from 94L will spread inland into Central America Tuesday and Wednesday, bringing 2 – 4” of rain with isolated higher amounts.

Tara
Figure 1. Infrared image of Tropical Storm Tara at 1415Z (10:15 am EDT) Tuesday, October 16, 2018. Image credit: NASA/MSFC Earth Science Branch.

Tropical Storm Tara scraping the Mexican coast

Not much bigger than a Midwest thunderstorm complex, tiny Tropical Storm Tara continues to spin just off the Mexican coast, with top winds of 45 mph. Tara’s center was located about 30 miles south-southwest of Manzanillo at 11 am EDT Tuesday, with tropical-storm-force winds that extended only 25 miles from the center. Pockets of heavy rain were pulsing along and near the coast, mainly north of Tara’s center. About 30 miles northwest of Manzanillo, the coastal town of La Manzanilla reported 1.30” of rain on Monday and another 3.32” through Tuesday morning. NHC is predicting isolated totals of up to 15” could fall over parts of Colima and western Jalisco states, bringing a risk of localized flash flooding.

Tara is expected to drift northwest, hugging the coast near Manzanillo this evening before moving further offshore on Wednesday. Because Tara is so small, it is unlikely to intensify while close to land, and it could easily dissipate by Wednesday, as predicted by the GFS and European models. Small systems can change quickly, though, and a period of strengthening cannot be totally ruled out. In the unexpected event that Tara survives its encounter with the coast, the 12Z Tuesday SHIPS model shows more favorable conditions offshore: wind shear is light to moderate (10 – 15 knots) and the nearby waters are very warm (around 30°C or 86°F). However, the HWRF model, which shows Tara surviving its trek away from the coast, continues to weaken the storm even then.

On the doorstep of record ACE for the Eastern Pacific season

As of 11 am EDT Tuesday, the Eastern Pacific (between the International Date Line and the Americas) had racked up 294.6 units of accumulated cyclone energy (ACE), compared to the average year-to-date total (1981-2010) of 121 and the average full-season total of 132. As calculated by Phil Klotzbach (Colorado State University), the highest ACE on record for any season is 295.2 (1992), followed closely by 288.1 (2015).

Models agree that the tropical wave associated with 94L could help spawn yet another named storm in the Eastern Pacific by this weekend. In fact, NHC is calling for a 90% chance of development over the next five days. If Tara does not push the Eastern Pacific into the #1 spot for ACE on Tuesday or Wednesday, then the next system very likely will.

The 2018 hurricane season in the East Pacific (east of the Date Line) has now had 20 named storms, 11 hurricanes, and 9 intense hurricanes. An average season has 15 named storms, 8 hurricanes, and 3 intense hurricanes, so we are well past those benchmarks with several more weeks of hurricane season remaining. The all-time records in the East Pacific are 27 named storms (set in 1992), 16 hurricanes (set in 2015, 2014, and 1992), and 11 intense hurricanes (set in 2015).

Bob Henson wrote the Eastern Pacific section of this post.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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Dr. Jeff Masters

Dr. Jeff Masters co-founded Weather Underground in 1995 while working on his Ph.D. in air pollution meteorology at the University of Michigan. He worked for the NOAA Hurricane Hunters from 1986-1990 as a flight meteorologist.

emailweatherman.masters@gmail.com

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