More than meets the eye in hurricane bombing debate
On October 25th in 1952, Gordon Clouser flew a small Luscomb airplane into hurricane Fox in an attempt to weaken the storm. Clouser, a pilot and meteorology teacher had found his calling as a rainmaker and had developed a secret formula of chemicals that he dispersed into hailstorms to protect farmers from hail damage. He had also flown over emerging tornado clouds and possibly prevented dangerous tornadoes from forming. His main interest was hurricanes, though. Seeing the chance to manipulate the perhaps last hurricane of the season, he decided to take the risk and fly in with his small plane. He dropped his secret chemicals into the storm and turned back. The headwind of the hurricane was strong and after 26 minutes on the radio with the base, his last message was ’Out of fuel, descending, give my love to my wife and family’.
Hurricane Fox did take an erratic turn and weakened soon after his actions, but whether this was due to interaction with the Bahamas as thought by some meteorologists at the time, we won’t know for sure unless we come up with some very clever meteorological forensics.
Even before Clouser in 1947, the American military had dropped dry ice into a hurricane that was heading out to sea, west to east. After a clear initial visual change in the clouds, the hurricane took an erratic turn and made a disastrous landfall in Savannah, Georgia. Once again, the effect of human intervention was hard to pinpoint as such erratic turns also happen naturally. After a decade and a half of low profile, a large American government project experimenting with hurricane modification called Project Stormfury started. Clouds were seeded with silver iodide that resembles natural ice nuclei. The idea in the first stage was to de-stabilize the main vortex and later to surround it with a new wall of clouds that would suffocate the original eyewall, where the roughest weather occurs. A total of four storms were seeded on eight days with significantly weakened winds observed on four out of the eight occasions. On the four ineffective days, the seeding either missed the target or the storms did not have well-defined eyes. Once again, efforts to separate natural and human effects remain inconclusive to this day. However, as a result of Project Stormfury, we know much more about hurricanes and can forecast them better.
The story of Hurricane Unwinder Ltd also started with research on downgrading hurricanes. Our concept to downgrade hurricanes involves vortex modification through turbulence. Modifying the internal structure of a vortex is a very niche topic in physics with the only industrial application perhaps being the spiralling vortex inside experimental fusion reactors. There the turbulence is suppressed to keep the vortex energy tightly concentrated to its core in order to avoid it reaching the vessel walls. In a hurricane, the opposite is desirable. Cross-flow turbulence of certain types diffuses momentum outward and weakens the low pressure area in the core of the storm.
When we started doing research on hurricane downgrading from the safety of our office with mathematical models, many people asked us what would happen if one dropped a nuclear bomb in a storm. It was usually accompanied by a small sarcastic smirk, but seemed like there was a pinch of genuine curiosity involved as well.
Hurricane intensity forecasting is particularly challenging for current weather forecast models despite it being very important. Damages depend exponentially on intensity. Our machine learning intensity forecast uses high-resolution satellite images and resolves the core of the storm in way more detail than a standard weather forecast. Yet the reason we were interested in these details in the first place was that we were exploring whether we could seed, spray, cool, barricade or bomb them.
The idea revived by US president Trump to downgrade hurricanes has good intentions behind it. Hurricanes, typhoons and tropical cyclones cause tens of billions of euros worth of damages each year, making hundreds of thousands of people homeless and causing numerous casualties as well. Suggestions of the sort usually cause an avalanche of objections and scientific skepticism. Except for the risks involved, the opposition might also have its roots in the history of weather modification.
Rain enhancement through cloud seeding hit stormy opposition after an initial wave of excitement especially in the 1960s, not least by academics who pointed out the difficulties in evaluating statistics of rainfall that is highly variable depending on the environment and even on individual clouds. Project Stormfury’s annual reports also started turning more and more pessimistic. In the three decades between 1970 and 2000, the American research budget for weather modification plummeted from 19 million to 0.5 million USD. Only lately does weather modification research experience new lift, motivated by a thirst for water resources. China is seeding clouds in the Tibetian plateau in an area five times the size of Finland to catch the rainfall in their river basins downwind. The effort is supported by a fleet of satellites and supercomputer models. The United Arab Emirates have funded nine large research projects of 5 million USD each, one of them in Finland.
The academic tide finally turned last year, 2018 when top scientific journal Science stated that cloud seeding indeed works at least in some conditions. Perhaps the time is also getting ripe to revive the enthusiasm of one day downgrading dangerous hurricanes to avoid the senseless destruction they are causing.
Unlike in the 1960s, we now have supercomputers for simulations and fleets of modern satellites that can be used to track and understand hurricanes safely until we are sure that we know what we are doing. The best way to downgrade a hurricane will probably be to mimic such events from nature. One scientific study recognized frequently occurring transitions from an intense regime to a significantly less intense one happening as quickly as in 1 hour due to turbulent mixing. Dry air entrainment at mid-levels of the atmosphere that frequently dries up the energy source of hurricanes also involves turbulence, which if understood well enough could be caused intentionally. With the new set of tools created in weather modification, satellite data analysis and computer simulations, we might just be able to do it without nukes.
Sources
Ivan Ray Tannehill: The Hurricane Hunters, Dodd, Mead and Company, New York, 1956
Willoughby, H. E., D. P. Jorgensen, R. A. Black, and S. L. Rosenthal: Project STORMFURY, A Scientific Chronicle, 1962–1983, Bull. Amer. Meteor. Soc., 1985
Roelof Bruintjes: A Review of Cloud Seeding Experiments to Enhance Precipitation and Some New Prospects, Bull. Amer. Meteor. Soc., 1999
United Arab Emirates Research Program for Rain Enhancement Science, http://www.uaerep.ae/
Kossin, J. P., and M. D. Eastin, 2001: Two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall. J. Atmos. Sci., 58, 1079–1090. PDF file
