How Texas weather is influenced by the Pacific, not just the Gulf

The number of hurricanes or tropical storms from the Gulf of Mexico reaching Texas decreases significantly in October and November, the end of the Atlantic hurricane season.

Tropical humidity still prevails in Texas during these fall months. A key difference, however, is that instead of directly hitting the Texas Gulf Coast, hurricanes in October often hit the west coast of Mexico, and the remnants of these storms can cause heavy rainfall and flooding in the southern half of Texas.

Just last month, Tropical Storm Ileana formed off the west coast of Mexico and rolled north along the coast of Baja California Sur before erupting in northern Mexico. The tropical system never entered Texas, but much of the storm’s remaining tropical moisture was carried east into far southern Texas, producing showers in an area from Del Rio to Corpus Christi.

Track it: Whenever the next named storm develops, you can track it with our interactive Texas Hurricane and Tropical Storm Tracker.

While this tropical storm wasn’t a major concern for the Lone Star State, this region of the Pacific Ocean is becoming an area to watch as we move deeper into October.

We all know about Harvey in 2017, Ike in 2008, and Rita in 2005, which made landfall in late August or the month of September, which is generally considered the peak of hurricane season.

But who can remember Pamela in 2021, Patricia in 2015 or Madeline in 1998? These are not well-known names, but they developed in the eastern Pacific in October and drenched Texas with rain.

Although Pacific storms like these no longer pose a threat of winds or storm surge when their remnants reach Texas, they can still cause very heavy rainfall and devastating flooding.

As Texas transitions from late summer to early fall, the weather pattern in the upper atmosphere begins to change and the frequency of tropical systems originating from the Gulf of Mexico decreases significantly.

The polar jet stream in Canada is slowly moving slightly south. Because of this, areas of low pressure and associated cold fronts have a greater chance of affecting the Lone Star State through October.

The more frequent cold fronts act as a barrier, keeping tropical systems in the Gulf away from the Texas coast and directing them toward the eastern Gulf of Mexico and the East Coast. For this reason, Florida and the East Coast are more likely to make direct landfall in October and November than the Texas Gulf Coast.

Meanwhile, the Eastern Pacific hurricane season remains strong through the end of October. Whenever these storms turn north toward Mexico, the likelihood of South Texas receiving significant tropical moisture is greatest.

One of the worst cases of a Pacific storm bringing heavy rainfall to Texas occurred October 16-19, 1998. Hurricane Madeline had peaked as a Category 1 hurricane in the eastern Pacific, just off the west coast of Mexico. The storm never made landfall, but tropical moisture from Madeline moved into South Texas and interacted with a stalled cold front. The result was one of the worst flooding disasters in San Antonio’s history.

San Antonio recorded 15.61 inches of rain, including a daily record 11.26 inches that fell on October 17, 1998. Precipitation peaked near Lockhart, where 29 inches of rainfall was recorded. This flooding event caused 31 deaths across South and Central Texas.

Madeline cannot be held solely responsible for this flooding event as many other meteorological factors played a role. However, the tropical system was a major factor providing most of the moisture.

A few years later, another Pacific hurricane, Patricia, rapidly strengthened in late October 2015, reaching 215 mph winds, the highest ever recorded anywhere in the world. Patricia weakened to a Category 4 storm before making landfall on the west coast of Mexico. It continued to weaken before its remnants made their way to Texas.

Flooding has drenched many areas across Texas. Austin and San Antonio recorded 4 to 6 inches of rain October 23-25. Houston recorded 7.58 inches of rain. But those overall numbers pale in comparison to some areas further north. Corsicana received 21.05 inches of rain due to remaining storms in Patricia, forcing a closure of Interstate 45.

Other notable storms include:

• Hurricane Pamela: In October 2021, Pamela hit the west coast of Mexico as a Category 1 hurricane. It weakened quickly, but its remnants provided moderate rainfall across parts of Central and South Texas. Between October 13 and 15, San Antonio recorded 4.22 inches of rain and Austin recorded 2.92 inches.
• Tropical Storm Olaf: Similar to Hurricane Madeline, moisture from Tropical Storm Olaf in the Eastern Pacific contributed to 6.06 inches of rain in San Antonio in October 2009.