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Erin Pays an Unexpected Visit to SCMS

A field program documenting embryonic cumulus caught the other end of the growth spectrum on 1 August. Hurricane Erin came ashore south of Melbourne, Florida, where the Small Cumulus Microphysics Study (SCMS) was based during July and early August. Several dozen staff from the Atmospheric Technology Division (ATD) went to Florida for the study, whose lead principal investigator is Charlie Knight (Mesoscale and Microscale Meteorology Division). Other institutions involved include the New Mexico Institute of Mining and Technology and the Universities of California, Los Angeles; Chicago; Illinois; Oklahoma; and Wyoming.

The CP-2 radar, soon to be mothballed, caught one of the most exciting events of its long lifetime. Erin's eye passed 85 kilometers south of the radar. Cocoa Beach and Patrick Air Force Base were under mandatory evacuation orders, so most NCAR staff were forced to leave. The NCAR-based C-130 aircraft took refuge in the Carolinas at Raleigh- Durham International Airport. Meanwhile, nine radar technicians and scientists battened down with the radar for 31 hours of continuous data collection.

"Winds at the radar were estimated at about 60 knots [31 meters per second], which the CP-2 dome had no problem with," reports Jim Wilson (ATD). "There were many rain bands and a well-defined eye. As Erin moved inland, a massive, rotating, stratiform area developed which eventually filled the eye." Although cloud tops were relatively low and no lightning was observed in the area, "some of the bands had rotating showers that produced small tornadoes."

This appears to be the first time a dual-polarization radar has documented a hurricane. These radars alternate signals that are polarized at right angles to each other, allowing scientists to deduce the shape and type of precipitation or cloud droplets. "This should be an excellent data set for evaluating polarization techniques to measure rainfall," says Jim. Aside from the hurricane, SCMS gathered much useful data on the incipient phase of cumulus clouds, according to Charlie. The project concluded on 14 August. --BH

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Edited by Bob Henson, bhenson@ucar.edu
Last revised: Wed Mar 29 17:37:11 MST 2000