Advertisement
Brian Hirth, research professor with the National Wind Institute at Texas Tech University, stands next to one of the 14 StickNet platforms deployed to analyze the effects of Hurricane Harvey. Photos: Brian Hirth/Texas Tech University Hurricane Research Team

Thirty inches of rain, occasional tornadoes, and swirling floodwaters tore through parts of Houston, the fourth-largest city in the United States, over the weekend. And yet Hurricane Harvey keeps coming.

The Texas Tech University Hurricane Research Team has more than a dozen mobile weather stations measuring and recording the arrival of the unfolding disaster. The storm has bucked some assumptions of tropical hurricanes emerging from the Gulf of Mexico – and continues to surprise some forecasters.

Brian Hirth, a research professor at the National Wind Institute at Texas Tech, explained some of Harvey’s unique perils from the real-time data even as the storm continues to drench eastern Texas.

Laboratory Equipment (LE): What is most notable about this storm?
Brian Hirth (BH): No two hurricanes are the same and Harvey is certainly another example. Many times hurricanes have reached peak intensity and are weakening as they make landfall in the U.S. and enter a more hostile atmospheric environment. Atmospheric conditions surrounding Hurricane Harvey were very supportive all the way up to landfall, allowing for a continuous, rapid strengthening trend to a Category 4 Hurricane on the Saffir-Simpson hurricane wind scale. Following landfall, the atmospheric pattern steering Harvey collapsed, allowing the storm to meander over south Texas while slowly weakening. This resulted in an extended duration of high winds and torrential rainfall for southeast Texas.

LE: Why has the National Weather Service characterized this as something not seen before?
BH:
I suspect the NWS is referencing the rainfall totals, which are now approaching historic levels in the Houston area (as of mid-day Monday). Meteorologically speaking, typically when a hurricane makes landfall in the U.S., it is being steered or “picked-up” by a mid-level trough that tends to accelerate the storm eastward away from the landfall region. In this rare case where the steering flow is weak, Harvey is just meandering near the coast, allowing for the onshore flow (east) side of the storm to continue to draw Gulf of Mexico moisture up into the southeast Texas region. The result is the catastrophic flooding rains we are currently witnessing on the Texas and Louisiana coastlines.

LE: What are the main impacts to Houston? Is it the precipitation, the storm surge, or a combination of the two?
BH: The storm surge associated with Harvey was not as extreme as other Gulf Coast storms we have seen in the recent past (e.g. Katrina, Rita, Ike), and Houston was separated a large enough distance from the center of Harvey at landfall that storm surge impacts were likely minimal there. The torrential rains and inability for local drainage to appropriately keep up is the root cause of the flooding in Houston.  That’s not to say there are design issues, rather the incredible rainfall rates (several inches per hour) are nearly impossible for any drainage system to handle over a long duration.

 

"As we began the process of retrieving the platforms we deployed, it quickly became apparent that Harvey was immediately a life-altering event for so many."

 

LE: Have there been challenges to this research? (Challenges that have surpassed that of other storms investigated by the Texas Tech University Hurricane Research Team)
BH:
Our efforts are focused on making wind measurements during the landfall of hurricanes and our program has been doing so since the late 1990s. We are trying to both document where the strongest winds occur and the spatial distribution of the winds. When we deploy our instrument platforms (StickNets), we generally look for sites that have open or marine exposure, and are high enough to stay out of any storm surge threat. The region of south Texas that experienced the highest winds of Harvey was generally rural farming areas, which provided deployment sites conducive to our efforts. That said, it’s a considerable amount of work identifying suitable deployment locations, making sure the platforms are adequately spaced relative to the expected size and distribution of the storm's wind field, and then being flexible enough to adapt as the forecast landfall point shifts, and the structure of the storm and its winds evolve. So those challenges are always present and unique on a storm-by-storm basis.

LE: How does this storm compare (power, damage, destruction, characteristics, any other markers) with other major recent storms such as Katrina, Sandy, Andrew in 1992, etc.?
BH:
While the most significant impact of Harvey in terms of population and dollars will inevitably be a result of the flooding in Houston, Harvey brought with its initial landfall significant winds to the areas between Corpus Christi and Port Lavaca. The wind damage we observed in those areas rivals any I’ve seen dating back to Katrina in 2005. The small coastal towns such as Aransas Pass and Rockport, among many others, are completely devastated. As I said previously, Harvey was a bit unique in that as it approached the coast it was rapidly strengthening all the way through landfall. Not to downplay the areas that were impacted by the strongest winds, but had the landfall placed the wind maximum over a larger population center, the extent of the wind damage would have likely been historic.

LE: Overall, what is the sense of this storm on the ground? Are there any notable aspects to the flooding or devastation?
BH: As we began the process of retrieving the platforms we deployed, it quickly became apparent that Harvey was immediately a life-altering event for so many. In the hardest hit areas, entire homes were destroyed, and those are always hard images to process. While our deployments were well south of Houston (Corpus Christi to Point Comfort), I can’t even imagine the ongoing crisis there. As someone fascinated by weather, these types of events are really neat and interesting to me. I have a tremendous respect and appreciation for the devastating impact they can cause. We have so much to still learn about how to make our buildings and communities more resilient to storms like Harvey. We’re never rooting for this type of disaster to happen, but if it’s going to, we want to be there to collect valuable measurements to advance the science.

Map showing where the StickNet deployments were located relative to the Corpus Christi WSR-88D radar representation of Hurricane Harvey near the time of landfall.

Laboratory Equipment magazine also spoke with Jeffrey Chagnon, an assistant professor of meteorology at Florida State University’s Department of Earth, Ocean, and Atmospheric Science. Chagnon explained how Hurricane Harvey continues to throw a curveball to weather experts – and why Houston is susceptible to the historic effects.

Jeffrey Chagnon: "Harvey is an exceptional storm in the sense that it has been effectively stationary near the coast of Southeast Texas since Saturday and is not expected to move very much over the next few days. Tropical systems are steered by the pre-existing flow of the background environment. Normally the steering flow ensures that a storm doesn't linger in any one place for too long. Unfortunately, Harvey is situated in a dead spot in the steering flow. Only slow movement is expected over the next few days.

"Harvey was a major hurricane with devastating winds at landfall, but the most significant impacts of this storm concern rainfall. The persistence of such intense rainfall in Southeast Texas over such a long period is what makes this an exceptional event. To make matters worse, Houston Metro is particularly prone to flooding because it does not drain very well, partly because it is a large mass of concrete on top of a bayou. 

"It should be emphasized that the forecasts of Harvey have been very good, once again demonstrating the skill and talent of our operational weather prediction community. Without a doubt, many lives have been saved because of the forecasts as well as the action of first responders. A question that will surely and rightly be asked in the aftermath is whether the flood preparation and mitigation strategies were designed adequately to deal with an event of this magnitude. I am not in a position to pass judgment on that issue with respect to this event, but it is fair to say that rapid urbanization in flood-prone regions has the potential to exacerbate flooding in events much less extreme than Harvey."

Advertisement
Advertisement