Yesterday the NASA Global Hawk flew over Hurricane Earl for about 8 hours. It took off from NASA's Dryden facility at Edwards AFB near Mojave, CA at 9 pm the previous evening. After climbing above 50,000 feet to get out of airline traffic lanes, it flew across the southern US to the Gulf and across Florida, and acquired the storm 8 hours later. At that time it had climbed to 60,000 feet. Although the Global Hawk flies itself per a flight plan stored in its computer, there are experienced pilots monitoring it from a control center at Dryden, and from time to time they intervene by uploading a revised flight plan. There is no joy stick, everything is done with keyboard and mouse via a graphical user interface (GUI). One of the things they look for is cloud tops near or above the flight altitude, which might be associated with dangerous turbulence that could possibly endanger the plane. There is a forward-looking video camera as well as a downward-looking fish-eye lens camera, and they are used in daylight. There is also an accelerometer on board.

One of the payloads on the Global Hawk is the HAMSR instrument (see the HAMSR home page), and we had three shifts covering this 24-hour flight. Yours truly hit the freeway at 3 am to catch the flight portion over the storm. We got some really good measurements while flying straight across the eye several times, since it turned out that the cloud tops were well below flight altitude, and we now have a data set that we will use to study the eyewall replacement process. The image is a composite, showing a snap shot from the Global Hawk belly camera while approaching the eye (the upper edge looks forward and the lower edge is straight down), a picture of the Global Hawk, and a sample quick-look image from HAMSR while passing over the eye. The eye is the blue-green area (ocean surface plus light clouds) surrounded by an orange-red ring (clouds). The blue patch just north of the cloud ring indicates a convective burst, probably a thunderstorm. That is confirmed by the pink crosses, which indicate lightning. There are more HAMSR images at the HAMSR browse page and at the JPL hurricane portal.