Michael Black, a research meteorologist in the Hurricane Research Division at NOAA, says the biggest impact of the project should come from NASA's Global Hawk, an unmanned aircraft carrying new scientific instrumentation. Unlike manned aircraft, the Global Hawk can fly for up to 30 hours and at high altitudes; it can also gather more detailed data than a satellite and can be stationed to monitor an area for extended periods. (Technology Review wrote about the robotic plane's capabilities here.)

"The Global Hawk can sit above the hurricane and peer into it to gather the information we don't have about the top of the storm," Black says. At the top of the hurricane, wind flow is reversed, so instead of spiraling in from the center, the winds spiral out. A balance of wind flow between the top and bottom of a storm is what enables it to intensify from a cyclone--a closed area of rapid wind circulation--to a hurricane.

The Global Hawk took off from Edwards Air Force Base in California on Wednesday evening to make its first flight over Hurricane Earl and monitor the storm for 24 hours.

The Global Hawk payload includes two new instruments developed by NASA, one to gather horizontal wind vectors and ocean surface winds, and a second to measure and create a 3-D distribution of temperature, water vapor, and cloud liquid water. (A third new NASA instrument that measures strong ocean surface winds through heavy rain will be onboard the WB-57 aircraft, also being flown by NASA.) These three instruments are more sophisticated and will provide better measurements than anything now used, says Heymsfield.

T.N. Krishnamurti, a professor of meteorology at Florida State University, says the new hurricane monitoring mission is unique and will help researchers build more accurate models of future storms. Having a better handle on the track and intensity of storms can help emergency management groups better prepare. "So many things happen in a hurricane that are complex--a warm core forms, high wind speeds, rain bands, and ocean currents are rampant--and we have lacked observation of all these things together," says Krishnamurti.