Building the H3T Stormchaser

Because nobody really knows for certain yet what happens inside a tornado, the best way to learn is to measure conditions with sensors in “pods” and “stick pods”, according to Dr. Joshua Wurman, a long-time tornado researcher and radar expert. These pods complete data gathered by mobile Doppler radar and “mesonets”, vehicles with sensing instruments attached to masts. Placing the pods into the center of a tornado must be done with vehicles that can drive safely into the projected path of a twister and then leave an instrument pod behind.

During this process the vehicle is likely to encounter heavy rain, hail, flash flooding and road and shoulder washouts. In addition, high winds carry dust and debris that can be dangerous. The HUMMER H3T was chosen to be a member of the VORTEX2 mission this year, the largest tornado study ever, because it has unique capabilities that are ideal for precision placement of instruments in severe weather. First, the vertical-oriented windshield is much less susceptible to large hail penetration than other vehicles, and the small side glass area makes the glass stronger to resist dust and debris. The high ground clearance of the H3T and other features allow it to ford a 24-inch flood, and wide siping of the P265/65R18 tires available in the ZM6 Adventure Package help keep the vehicle from hydroplaning. This package also includes front and rear locking hubs when the four-wheel-drive system is in low range, which gives the H3T the option of navigating very bad roads during pod placement and retrieval. “We can send the Hummer into places where we haven’t sent our other probe vehicles before,” said Wurman.

To carry the three 120-pound pods inside the H3T safely through wind and weather, a frame of 1 and ¼-inch square steel tubing was constructed and sheathed inside with thick commercial marine plywood, bolted in place every 18 inches. In addition, a DiamondBack H3T bed cover tops off the protective cage to protect the pods from hail and other flying debris that often accompanies tornados and severe weather.On top of this sturdy box are two antennas for communications and a radio tracking system. Inside the H3T are a voice transceiver and a data transceiver, as well as three GPS receivers and two cellular transmitters, in addition to the standard OnStar system and a separate voice cellular phone. In addition, serial cables from the pods in the back of the H3T to the passenger compartment let meteorologists on board download data recovered from the pods’ data acquisition black boxes into laptop computers. Two laptop computers are mounted inside the H3T, one in front of the front passenger, and one accessible to two rear passengers.

Further, there is a public service radio scanner and weather radio. One data GPS is relegated to the duty of recording exact GPS positions of each pod that is deployed and for recording local weather conditions through two wind speed sensors mounted on the top of a 13-foot steel mast, braced to the pod cage. Grote LED wide beam lights cut under thick rain, and an amber strobe light on the H3T roof and amber rotating beacons on the rear of the pod box alert other traffic in low visibility conditions.

The H3T is expected to cover more than 15,000 miles while it is in use by the VORTEX2 project.

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