At 28,000 feet over Tropical Storm Guillermo a bang is heard within the Hurricane Hunters WC-130J.
At 28,000 feet over Tropical Storm Guillermo a bang is heard within the Hurricane Hunters WC-130J.
On most flights, such a sound might spur concern for the average passenger, but on this flight of the 53rd Weather Reconnaissance Squadron the sound signals the beginning of data collection that will assist Central Pacific Hurricane Center forecasters in narrowing the cone of uncertainty as Guillermo approaches the Hawaiian Islands.
Falling at a rate of 2,500 feet a minute, the dropsonde — a Pringles can-sized contraption that has some resemblance of a used roll of paper towels — makes its way through Guillermo down to the ocean surface. On its 10-minute solo mission, the highly sophisticated device collects an array of data including wind speed and direction, temperature, humidity and barometric pressure before it hits water.
In all, 17 dropsondes were ejected from the WC-130J late Monday and early Tuesday amid four alpha patterns that took the U.S. Air Force Reserve aircraft through the center of the storm to as low as 5,000 feet above sea level.
All that data streaming in every half second helps Central Pacific Hurricane Center forecasters more accurately predict not only the potential track for a tropical cyclone, but also its strength and structure, says Senior Airman Sgt. Nathan Calloway, who is operating the dropsonde tubes.
“We’re like a test tube in a lab,” Calloway says, raising his voice just enough to hear over the roar of the WC-130J’s four turboprop jet engines. “We’re collecting tons and tons of data that satellites just can’t pick up. All they (forecasters) see is the top of the storm (using satellite), we fly underneath the storm, 5,000 to 10,000 feet at times.”
It can also result in savings to taxpayers because the cone of uncertainty for the forecast track can be narrowed, prompting fewer evacuations, he adds.
“Evacuating one coastal mile costs about $1 million,” Calloway said, explaining that narrowing the forecast for Hawaii could mean one island needs to evacuate while another does not.
On this night-time flight — the fourth the crew has taken through Guillermo since arriving from Biloxi, Miss., Saturday — Guillermo showed little change from earlier in the day, but has weakened since Sunday when it was circulating maximum winds around 100 mph, said Aircraft Commander Jim Hitterman during a brief period away from the flight deck.
“It seems to be decreasing in size at this time,” he said.
During the overnight mission, the Hurricane Hunters found Guillermo was packing maximum winds around 85 mph at flight level and taking a more northerly track then previously thought, Kyle Larson, the squadron’s Aerial Weather Reconnaissance Officer, said shortly before the WC-130J touched down in Honolulu. The five-man crew is slated to take off for another round of data collection Tuesday morning.
With the data added to forecast models, Central Pacific Hurricane Center forecasters were able to adjust the forecast track, putting Guillermo on a path north of the Big Island. The tropical cyclone is now forecast to pass more than 215 miles northeast of Hilo Wednesday, said Tom Evans, acting director at the Honolulu-based hurricane center.
“The track has for the last several cycles shifted farther to the north, or away, from the islands,” he said, noting that the previous update issued several hours earlier had the storm passing about 170 miles northeast of Hilo. “The aircraft data is invaluable. The recon they provide gives us a much better idea of where the center is and that data also goes into the forecast models, which allows us to give better forecasts. With that recon data we are more confident than with just the satellite data.”