Follow the progression of events on May 3, 1999 from initial outlooks for the day to several status messages issued during the event and field operations. The following photographs were taken by Daphne Zaras during the intercept.

Unofficial Summary from Probe 1

by Daphne Zaras

Three VORTEX-99 crews left Norman, Oklahoma at 1:30 p.m. and drove southwest to near Lawton, Oklahoma in time to see the initial stages of the storm that produced a continuous, deadly tornado which tracked from near Chickasha to Moore and Del City in the Oklahoma City metro area.

The teams observed the first, brief tornado produced by the storm near Elgin, Oklahoma and were in place for scientific data collection for several subsequent tornadoes which formed prior to the Oklahoma City metro tornado. The second, or perhaps third tornado produced by the storm lasted over 15 minutes and was surrounded by mobile mesonet vehicles. VORTEX-99 collected valuable data on this tornado as the new circulation in the storm organized and began forming weak tornadoes. The storm was doing what scientists call "cycling": the original circulation had spun off toward the back side of the storm while a new circulation formed. The new circulation became the third, or possibly fouth tornado produced by the storm, and also was responsible for what became the Chickasha-Moore-Del City, Ok tornado. The teams left the storm near Chickasha as the deadly tornado developed in favor of another storm which was over a good road network west of Chickasha. The second, western storm had already produced a tornado and was clearly going to continue to produce tornadoes.VORTEX-99 intercepted 4 to 6 tornadoes on the second storm, for a total count of approximately 12 tornadoes on two storms.

VORTEX-99 had 3 cars surrounding up to a dozen tornadoes on Monday. Key regions sampled included the hook region (behind the tornado) where the air is wrapping around the back side of the thunderstorm. This region is also responsible for the "hook echo" seen in radar reflectivity which meteorologists often point out on TV. One mobile mesonet was able to traverse the hook region of the storm for three different tornadoes. Another mobile mesonet was in close proxmiity to several tornadoes and on all sides at one point or another, including just east and just north of the tornado, two regions the PIs were wanting data from.

VORTEX-99 scientists are in the process of analyzing the data. Meanwhile, VORTEX-99 continues operations through June 15.

VORTEX-99

Dr. Erik Rasmussen (NSSL/CIMMS) and Dr. Jerry Straka (OU) are the Principle Investigators (PIs) for VORTEX-99, a small follow-on to the original VORTEX which took place in 1994 and 1995. They are still seeking definitive evidence to support any one of 4 hypotheses of supercell tornado development. Two of the four hypotheses were formulated by them; one of the two hypotheses is the result of data analysis from VORTEX. The Dimmit, Texas tornado in 1995 supports a combination of the two hypotheses they have. A primary goal of VORTEX-99 is to sample the region just north and east of the tornado, as well as in the hook region behind the tornado. VORTEX-99 will conduct seven to nine field operation days between April 30 and June 15th, 1999.

VORTEX-99 investigators are collaborating with Dr. Howard Bluestein (University of Oklahoma) who is operating a millimeter-wave Doppler radar from the Massachusett's Institute of Technology (MIT). The millimeter-wave radar has a resolution of 10 meters at 5 miles and will provide unprecedented data. Dr. Bluestein's team also collected data on the storms on May 3.

http://www.nssl.noaa.gov      last updated 3/9/09