October could go down as one of the wettest month in Texas history.
State Climatologist John Nielsen-Gammon said once final numbers are calculated, the recently completed month will likely go down as the second wettest month in the history of the state. This comes just one month after heavy rains statewide led September to be declared the third wettest month on record for Texas.
“We’ve actually had four of the wettest months in history within the past three and a half years,” John Nielsen-Gammon said Thursday. “Which would be extremely unusual, but we know there is a long term upward trend in rainfall across the state.”
Gammon said his expectation is based on preliminary numbers for precipitation across Texas. Finalized numbers are expected to come in some time next week, he said.
Locally, a Sherman co-op weather station received 10.32 inches of rain for the month of October — nearly double the 5.29 it sees on average. The weather station broke the 10-inch mark this week when the area saw about 1.4 inches of rain fall on Wednesday, the final day of the month.
By comparison, the same weather station received just over 10 inches of rain in September, tripling what the region normally sees for the month.
“Originally, you had September as the third wettest month on record, well, now it is fourth thanks to this October,” Nielsen-Gammon said.
Patricia Sanchez, a meteorologist with the National Weather Service Fort Worth office, said 2018 ranks as the fifth wettest September on record for the Sherman weather station behind 1981, 1926, 2009 and 1984, respectively. By comparison, 1981 saw just under 23 inches of rain fall across Texoma, solidifying its place as the wettest month locally.
Over the past two months, four of the 10 climate regions in Texas had at least one weather station report more than 30 inches of rain, with one recording more than 40, Nielsen-Gammon said. Bonham was among the areas that reported heavy rainfall, with about 32 inches recorded for the two-month period.
Since mid-August, more rain has fallen in south Galveston County than fell for the same period in 2017. This includes the rainfall that came with Hurricane Harvey, one year ago, Nielsen-Gammon said.
The state climatologist attributed the unseasonably wet October to the same conditions that led to increased rainfall in late September. Hurricanes and other storms, including Tropical Storm Sergio, made landfall in Mexico and spread significant moisture across it and Texas. This moisture then came into contact with stalled cold fronts leading to disturbances and storms.
Nielsen-Gammon said this moisture was not the main factor that led to the heavy rains, but said the moisture spread across the entire atmosphere and kept evaporation from occurring. This in turn led to stronger storms than were initially predicted.
Sanchez attributed the storms across North Texas to a series of cells and cold fronts that stalled over the region and continued to saturate the area for several consecutive days in early October.
With the wetter weather in recent years, Nielsen-Gammon said climate change may be another contributing factor. With regard to the state, the increased world temperature has led to increased evaporation and moisture in the air, which then travels to Texas and falls as rain under the right conditions.
El Niño may also have contributed to the increased rainfall in recent months. The weather pattern, which is based on surface water temperatures in the tropical Pacific, has been connected to increased rainfall in Texas, Neilsen-Gammon said. However, this alone would not be enough to explain the record-breaking weather, he said.
Nielsen-Gammon said El Niño could have continued influence on weather leading into the winter months. While the weather patterns typically mean wetter and colder weather in the winter for North Texas, Nielsen-Gammon said the lower temperatures are likely going to be offset by the effects of global warming, leading to a wetter but mild winter. With much of the state already inundated with moisture, he warned this could lead to runoff issues later in the season.