Cool front may come with price
Houston will get its first real cool front of the season Saturday, bringing wonderful weather to the region just in time for the Texans’ season opener on Sunday.
But the pleasant weather may come with a price. After the front moves offshore and into the southern Gulf of Mexico, some forecast models indicate it could develop into a tropical system next week.
For now, Houston will have a couple of messy days on Thursday and Friday before the cold front arrives. Atmospheric conditions favor rising air, and with abundant moisture the region should see scattered to widespread rain showers and potentially some severe thunderstorms.
The rains should be hit or miss enough that they don’t produce significant flooding, and most areas probably will see one-half to 2 inches of rain.
The front itself should arrive on Saturday, perhaps around noon, bringing an end to the region’s rain chances. This will be a classic front, with northerly breezes and drier, cooler air moving in right away.
Low temperatures on Sunday and Monday morning could fall into the low 60s for the northern half of the Houston metro area while remaining a bit warmer near the coast.
The drier air should be really noticeable, too. Whereas the relative humidity for most mornings in Houston this summer has been above 90 percent, it could fall to around 50 percent by Sunday morning.
Uncertainty in the Gulf
For the Texans’ season opener, tailgate conditions really couldn’t be much better. Expect highs on Sunday to climb only into the mid-80s, under mostly sunny skies.
The cooler and drier weather will hang around through Monday before a southerly flow returns from the Gulf of Mexico.
At that point, some forecast models suggest a remnant of the cool front, out over the warm, southern Gulf, may develop into a tropical system. This can happen because cold fronts themselves are low-pressure systems.
There remains a lot of uncertainty about what could happen, if anything, in the Gulf. It’s not out of the question the low-pressure system could strengthen into a tropical storm, or perhaps even a hurricane, before wandering back northward toward the Texas coast.
The European forecast model, one of the most respected, has intermittently shown a hurricane developing in the northern Gulf of Mexico off the Texas coast by Wednesday or so of next week. However, other models have shown lesser systems, or none at all, developing.
It’s difficult to have any confidence in these forecasts for two reasons.
First, six- and seven-day forecasts are the limit of a computer’s ability to predict the onset of tropical systems. Secondly, when the most important models don’t converge on a forecast, they should be treated with some skepticism.
A storm forming from a remnant front would not be unprecedented. Hurricane Alicia, which struck the Houston area in 1983, formed after an early cool front moved off the Texas coast and into the Gulf of Mexico.
The reality is, at this time of year, any low-pressure systems bear watching.
Forecast models not agreeing
Although the Gulf has remained quiet since Tropical Storm Bill came ashore along Matagorda Island in June, this Atlantic hurricane season isn’t over for Texas. The Gulf ’s water temperatures typically don’t peak until early September, and if wind shear values are low, systems can develop rapidly, as Hurricane Humberto did in 2007.
One of the reasons the forecast models can’t agree on the tropical development next week is that they’re divided on how high wind shear will be. Higher wind shear tends to rip storms apart by disrupting their circulation.
When it comes to tropical activity, however, the window is closing for Texas. Typically by the last week of September, storms that form in the Gulf of Mexico are pushed south into Mexico, or east of Texas. We’re not there yet, but we’re close.
With all that said, the most likely scenario for next week is that a disorganized low-pressure system wobbles around the Gulf of Mexico. This could bring some really good rain chances — potentially heavy rainfall — beginning later on Tuesday and into Wednesday into the upper Texas coast.