August 24, 1998 -- A converted DC-8 jet airliner, outfitted as a remote sensing laboratory, took weather researchers on an historic ride Sunday into the eye of Hurricane Bonnie as she churned in the Atlantic near the Bahama Islands.
And while looking Bonnie in the eye, she winked.
Ocean waves, whipped by Bonnie to 2.4 to 3.6 meters (8-12 ft) high, crashed ashore a few hundred meters from the runway at Patrick Air Force Base, Fla., where a DC-8 prepared for the first-ever NASA jet flight into the eye of an Atlantic hurricane on Sunday afternoon.
The jetliner, flying at 11 km (37,000 ft), was joined at the storm by a NASA ER-2 jet overhead at 19.8 km (65,000 ft), and a NOAA WP-3D Orion turboprop 4.6 km (15,000 ft). The NASA planes took off at 1:34 p.m. EDT on their seven-hour mission.
"This is a significant achievement for this hurricane study," said Robbie Hood, mission scientist from NASA's Global Hydrology and Climate Center in Huntsville, Ala. "We achieved our number one objective, that we could accomplish the tricky maneuver of placing all three NASA and NOAA aircraft in the study of the structure of the same storm at the same time."
The research program, called CAMEX-3, is a combined study effort including eight NASA Centers, NOAA, and a contingent of scientists from universities across the nation.
The aircraft performed four passes over the eye of the then-Category-2 storm, centered at 24.5 N, 71.4 W. Two of the passes were coordinated with a NOAA Orion passing below. Researchers could not see into the eye on two passes due to cloud cover, but recorded infrared images on each pass. The location of the eye was obtained by information passed along by scientists stationed at Patrick Air Force Base or aboard NOAA's Orion aircraft (like the one at right).
Once the aircraft reached the first hurricane of the 1998 season, the researchers encountered an unusual phenomenon: As the three aircraft flew in a stacked pattern, the eye wall turned from an oval to a oblong shape.
"This reshaping of the eye wall is characteristic of a hurricane that has stalled, and is preparing for a dramatic shift, either stronger or dying," said Dr. Ed Zipser, a weather expert from Texas A&M University.
Another impressive step was taken when NASA researchers gave Bonnie some eye drops. Ten small tubes containing miniature weather stations were dropped into Bonnie's shifting eye to check her vital signs &SHY; wind speeds, barometric pressure, and humidity levels. The tiny weather stations dropped into the middle of the eye verified the readings the DC-8 remote sensing instruments were reading at 11 km (37,000 ft).
Dropsondes can measure temperature, horizontal wind speed, pressure, and humidity from altitudes as great as 24 km (15 mi) until landing. The sondes themselves are marvels of miniaturization, only 7 cm (2.75 in) in diameter and 40.6 cm (16 in) long, and weighing just 400 grams (less than a pound).
The RSS903 dropsonde used in CAMEX-3 and other campaigns were developed by the National Center for Atmospheric Research and the German Space Agency (DLR) jointly developed the new model to use advanced sensors and to incorporate Global Positioning Satellite (GPS) receivers. This last feature gives scientists precise measurements of the sonde's location - including altitude - as it is carried along by a storm.
With Bonnie pushing towards the coast, wrote forecaster R. Wohlman, the Eastern U.S. is dominated by an intense high-pressure region. This is causing any shortwaves from the west to ride far north into Minnesota, Michigan, and Illinois. Otherwise, Ohio valley through Colorado is clear. Remnants of Tropical Storm Charlie, which charged ashore in the Texas gulf region, have slowed, filled and dropped lots of much needed rain over the southern half of the dry Lone Star state. I would expect that this moisture, which shows up well in the satellite water vapor imagery, would continue its westward movement. A large region of cloudiness and associated moisture is moving thou the New England states, and is forecast to slowly drift off shore. If there is a weakness in the extensive anti-cyclonic area over the U.S., it might develop just offshore, between that high and the one located in the mid-Atlantic.
Meanwhile, Bonnie continues to develop nicely. Winds up to 167 km/h (90 knots) sustained observed in the morning reconnaissance, but much to the consternation of the forecasters at the National Hurricane Center, forward motion has all but ceased. At 11 a.m. (15Z), Bonnie was centered at 24.2N, 71.6W and forecast to start moving northwest, then gradually shift northward. Bonnie's recalcitrance is causing the various forecast programs, which had once seemed to be converging on a fairly uniform track, to appear to be diverging again.
The above story is based on materials provided by NASA/Marshall Space Flight Center--Space Sciences Laboratory. Note: Materials may be edited for content and length.
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