South Texas Saharan Dust
July 27 - August 1, 2005
Images
- Satellite Animation
- Graph of 1-Hour PM2.5 Data South Texas
- Graph of 1-Hour PM2.5 Data San Antonio
- Graph of 24-Hour PM2.5 Data
- Graph of 1-Hour PM10 Data
- Graph of 24-Hour PM10 Data
Saharan dust moved into South Texas late on Wednesday July 27th and continued over much of South Texas and parts of Central Texas through August 1st. Fine particulate monitoring sites in Brownsville, Mission, and Corpus Christi measured 24-hour averages that reached Level Orange, Unhealthy for Sensitive Groups, based on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI)
scale. The PM10 monitoring site at Brownsville also measured a 24-hour average that rated as Level Orange on the AQI.
The highest measured 24-hour PM2.5 average was 46.1 micrograms per cubic meter (µg/m³) at Mission CAMS 43 for the 24 hours ending at 11:00 a.m. Central Daylight Time (CDT) on July 29th. The highest measured PM10 24-hour average was 167 µg/m³ at Brownsville CAMS 80 for the 24 hours ending at 1:00 p.m. CDT on July 29th. A weak cool front kept the dust cloud from advancing farther into the state. The front retreated enough to allow the edge of the dust cloud briefly into the San Antonio area mi-day on July 29th and again on July 30th mid-day.
The season for Saharan dust in Texas runs from June through August. The dust originates from large dust storms in the Saharan Desert and Sub-Saharan areas of western Africa. The dust from these storms is carried by the trade winds across the Atlantic Ocean, Caribben Sea, and Gulf of Mexico to reach Texas. This journey of over 6,000 miles usually takes about 10 to 14 days. Satellite imagery shows that the dust cloud that reached South Texas on July 27 began moving off of the western coast of Africa on July 16. Typically there are about three to six Saharan dust events that reach Texas with "Moderate" or higher fine particulate AQI levels every summer. Each event usually lasts about one to three days at affected locations.
