Last Friday Eric “Sci Guy” Berger, a former Houston Chronicle reporter and one of the most trusted dudes in local weather, warned on his Space City Weather blog that storms could bring heavy rainfall to areas already pummeled by last month's historic flooding.
He wasn't alone. With nerves still raw from the previous week's deluge and forecasters warning of a gnarly-looking line of storms that could form and crash into Houston, organizations across the city canceled Friday night and Saturday morning events. The City of Houston even announced which flood-prone underpasses and intersections it planned to block off before the storms hit.
But those heavy-duty rainstorms (thankfully) never came, at least not for most of the Houston area covered by the National Weather Service's flash flood warning for the weekend. So what happened?
Chalk much of it up to the uncertain nature of weather forecasting — it's not like the area didn't experience severe weather; it just didn't hit where and when and exactly as hard as forecasters warned that it could.
But according to Berger, last week's dire weather warnings late into the evening weren't due just to the uncertainty expected in any forecasting. In his blog (which you should read, especially when major storms are in the forecast) recapping last Friday's miss, he says local “soundings,” or weather balloons launched into the lower atmosphere for readings, might have tipped us off earlier in the day that predictions of heavy rainstorms overnight were probably overblown.
Just one problem: Houston doesn't launch weather balloons. Or, to be more specific, the local National Weather Service office, unlike in most other major cities in the country, doesn't do twice-daily balloon launches. What soundings we do get mostly come from the occasional launches out of Texas A&M and the University of Houston – that and some readings that come from airplanes flying in and out of the city that are equipped with special sensors. As Berger (a meteorologist who's covered weather in the region for more than a decade) wrote in this 2011 Chron story, the sounding locations closest to Houston are in Lake Charles, Louisiana, and Corpus Christi.
Dan Reilly, a meteorologist with the NWS's Houston/Galveston office, told us the weather service would love to launch balloons, but it's not something NWS has been given the budget for; he also made sure to say he and other weather-watchers at the station don't set their budget; "we just work within the resources that we're given."
As Berger wrote in 2011, Houston's not having regular balloon launches didn't really present much of an issue until the early 1990s when, because of restructuring within the weather service, the Victoria site where NWS used to launch balloons was moved south (according to Berger, the Victoria station was actually a pretty good spot to help forecast Houston weather).
Reilly told us soundings are just one of many factors plugged into the computer models used to forecast storms. Yes, local soundings can give you a more targeted local snapshot of what the air above the surface looks like at any given time, but that just augments the weather forecast; it doesn't radically change it. As Reilly told us, "There's always uncertainty in positioning exactly where heavy rain is going to be."
But Berger writes that local weather balloon launches could have given us a little more specificity later in the game — which, given the kind of storms and flooding we're apparently going to have every year or so now, might be kinda nice.
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To understand what Berger means, you might need a primer on how some of this stuff works. As Reilly explained to us, meteorologists last Friday were closely watching for a so-called "capping inversion," in which, in basic terms, a layer of warm air above the surface can act like a lid, or “cap," on surface moisture that would have otherwise risen to help form a thunderstorm. A lot of warm air, or a particularly strong "cap," can keep all that moisture being sucked off the Gulf from rising and breaking up in the lower atmosphere, eventually turning into a heavy downpour that floods Meyerland (again).
And local weather balloon launches give you pretty a good snapshot of what that "cap" looks like heading into a storm event.
On his blog, Berger says that without local soundings from the lower atmosphere, meteorologists had a hard time gauging how strong that cap was over Houston as the region braced for storms last weekend. As Berger wrote, “the ingredients were there for major rains over Houston, but an unexpectedly strong cap kept them at bay.” By last Friday evening, soundings out of Lake Charles showed a stronger than expected cap, and meteorologists – Berger included – adjusted their forecasts accordingly.
As Berger puts it: “I don’t regret those forecasts. They were just wrong. It happens in meteorology. And there’s no shame in having an honest conversation with readers about what went wrong.” But, if Berger's right, the government's not budgeting for weather balloon launches in Houston means that every time forecasters predict scary weather, we have to wait longer before we know whether to breathe a sigh of relief or hunker down for the worst.