A mild summer here in the Rio Grande Valley should transition into a traditional fall, with temperatures and rainfall hitting their normal numbers, meteorologists say.
The AccuWeather fall forecast is out, coinciding with the date set for meteorological fall, which lasts from Sept. 1 to Nov. 30. For the rest of us non-professional weather-watchers, the autumnal equinox occurs this year on Sept. 22, when calendar fall begins.
“For South Texas, by most accounts, it looks like a fairly seasonable transition to fall,” Brandon Buckingham, an AccuWeather meteorologist, said Monday.
La Nina effect
A prime factor in the weather for the next few months will be the El Nino-Southern Oscillation, known as ENSO.
ENSO is a measure of the temperature of a vast pool of water near the equator in the Pacific Ocean. When it’s abnormally warm, it is referred to as El Nino. When it’s cooler than usual, that’s La Nina.
Right now the central tropical Pacific is in a neutral state, coming out of a La Nina period.
Experts at the National Oceanic and Atmospheric Administration predict a 55-percent chance we will fall back into a La Nina cycle, which can alter weather patterns thousands of miles away.
Not only is a La Nina expected to develop, but it may also do so early in the season for the second year in a row, said AccuWeather senior meteorologist Paul Pastelok.
“Typically, we usually see La Nina come on about late fall to the winter season on average, but this year, it looks like it’s going to come in early just like it did last year,” Pastelok said.
La Nina’s return indicates the rest of the hurricane season could be above average in the Atlantic basin.
Storms to the east
The most active area for tropical disturbances through October appears to be setting up far to the east of the Rio Grande Valley.
“I know across South Texas, one of the major things to worry about are tropical threats,” Buckingham said. “Generally, with the set-up we’re anticipating, the main area of focus is primarily across the Southeast coast, the majority of the East Coast up toward the mid-Atlantic, with a general lower threat for the western gulf of Mexico, which should spell out good news across South Texas.”
Buckingham says the primary factors for a more easterly flow of tropical storms and hurricanes for the rest of the season are the persistent Bermuda high remaining stronger than usual and a dome of high pressure sitting over the western United States.
“If that (dome) centers itself slightly farther east, over the South Central plains, and if a tropical system were to track through the Caribbean, it would kind of have to skirt around the southern fringes of that upper-level high pressure which we generally would tend to think would suppress it farther south into Central America, rather than northward into the western gulf,” Buckingham said.
New storms, tracks
The AccuWeather prediction for most tropical disturbances to proceed north out of the Caribbean and up the East Coast appears to be holding for Tropical Storm Fred.
The storm started out in the Atlantic, and all computer forecast models show it on a northwesterly course which will send it across northern Cuba as it skirts the western coast of Florida on a northerly direction. Landfall prediction Wednesday afternoon was near Pensacola just after dawn on Monday, with Fred still at tropical storm strength.
A second disturbance, a tropical wave off the Azores in the eastern Atlantic, has a 40- to 60-percent chance of strengthening over the next five days. This tropical wave, for now, is forecast to directly follow Fred’s path into the Caribbean.
If those tracks hold, they could be indicators that the AccuWeather tropical forecast is on the right path and tropical development will stay to the east, and away from the Rio Grande Valley.
