NOAA GOES-8 Satellite Soundings
Analysis of Central Florida Tornado Event - 2/22/98 - 2/23/98

Overview of Event

During the evening of February 22, 1998 and the early morning of February 23, 1998, severe thunderstorms, which spawned numerous tornadoes developed in Central Florida, from Kissimmee eastward to near Daytona Beach, resulting in numerous deaths and injuries, as well as extensive property damage.

NOAA GOES-8 Lifted Index Fields

GOES-8 satellite soundings of atmospheric temperature, humidity and stability are generated at NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) on an hourly basis, using data collected by the 'sounder' instrument. Each sounding is representative of an area approximately 30 km x 30 km in size. Shown below are GOES-8 Lifted Index (LI) values (Degrees Celsius) for 1700 UTC - 2100 UTC 2/22/98, plotted over the corresponding NOAA GOES-8 visible satellite image, followed by the NWS numerical forecast model (ETA) LI estimates at the same sounding locations. Different colors represent ranges of LI values. LI's greater than 0 correspond to stable atmospheric conditions, less than 0 unstable. LI values less than -5C indicate extremely unstable conditions. The GOES-8 soundings indicated an area of increasing instability during this time period in Central Florida, with LI values decreasing from -1C to -8C. The corresponding numerical model forecast (ETA) estimates did not indicate this rapid de-stabilization. It is important to note that NOAA GOES-8 satellite soundings are available only in clear or partly cloudy conditions. As such they can be used to diagnose atmospheric conditions, such as stability, prior to severe weather outbreaks in the clear or partly cloudy conditions that typically occur during the morning and early afternoon. However, once severe weather develops, the associated cloudiness generally prevents the use of this data source.

NOAA GOES-8 Satellite Lifted Index at 1702 UTC (12:02PM EST), 2/22/98.

NOAA GOES-8 Lifted Index at 1802UTC (1:02PM EST), 2/22/98.

NOAA GOES-8 Lifted Index at 1902UTC (2:02PM EST), 2/22/98.

NOAA GOES-8 Lifted Index at 2002UTC (3:02PM EST), 2/22/98.

NOAA GOES-8 Lifted Index at 2102UTC (4:02PM EST), 2/22/98.

NOAA ETA Forecast Lifted Index Fields

NOAA ETA Forecast Lifted Index at 1702UTC (12:02PM EST), 2/22/98.

NOAA ETA Forecast Lifted Index at 1802UTC (1:02PM EST), 2/22/98.

NOAA ETA Forecast Lifted Index at 1902UTC (2:02PM EST), 2/22/98.

NOAA ETA Forecast Lifted Index at 2002UTC (3:02PM EST), 2/22/98.

NOAA ETA Forecast Lifted Index at 2102UTC (4:02PM EST), 2/22/98.

Conclusions

The NOAA/NESDIS GOES-8 soundings over Central Florida on February 22, 1998 accurately identified a region of maximum atmospheric de-stabilization, between 1700 UTC and 2000 UTC, associated with the outbreak of severe weather later that evening. The ETA forecast stability fields depicted a larger area of moderate instability over Central and Southern Florida, but failed to identify the zone of maximum instability associated with the tornadoes. Although the GOES-8 soundings helped localize the area of likely severe weather, their utility in this case was limited by high level cloudiness which moved over the area after 2000 UTC (3PM EST). The tornado outbreak occurred 8 - 10 hours later. Satellite soundings in cloudy areas are possible using microwave sounding technology, but this is not available on the current GOES satellite series. This capability would significantly improve the ability to monitor atmospheric stability changes prior to severe weather development in cloudy conditions. Further study is planned by NOAA/NESDIS scientists, and additional case studies will be made available in the future.

Comments are greatly appreciated. For more information contact:

Hank Drahos, FPDT Team Leader, NOAA/NESDIS hdrahos@nesdis.noaa.gov

Additional information on the Central Florida tornado event is available at the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin.

Web Page Last Updated: 02/01/99