Created and maintained by Roger Edwards, Storm Prediction Center
In this GOES-8 visible satellite image, note the milky gray plume extending north-south over the western gulf. This is smoke from a series of agricultural and forest fires over southeast Mexico and Central America. The smoke pall is dense enough to detect on infared imagery also (not shown). In fact, satellite estimates of sea surface temperature were hindered because of obscuration by the smoke. The smoke was moving northward in the moist sector (east of the dryline) of a cyclone centered over central Oklahoma. There is no obvious smoke west of the dryline because that air mass originated from the southern Rockies and high plains.
Burning of residue from the previous season's sugar cane and other crops is quite common in Central America and the Yucatan Peninsula during the spring. [To a lesser degree, this is also done in the cane fields of South Florida earlier in the year.] Farmers set the crop stubble aflame to reduce it to nutrient-rich ash, which enriches the soil. This must be finished in time for planting before the summer rainy season. Then, the ITCZ (Intertropical Convergence Zone) shifts northward from near the equator, and associated tropical waves help to increase thunderstorm occurrence. In the dry conditions of 1998 over that area, agricultural burning and forest fires went out of control in many areas, sending dense and thick smoke into the prevailing low level flow fields.
Throughout much of March, April and May 1998, those smoke plumes cast a thick pall of haze over the moist sectors of several cyclones that moved across the southern plains and southeastern U.S. The haze hindered storm spotters and weather observers who sometimes could not see thunderstorms in the distance and other important cloud features until the clouds were nearly overhead. Many such features are too small or do not contain enough precipitation to be detected by radar. Because severe storm warnings still depend on effective human spotting -- even in this era of Doppler Radar -- the Central American fires had the potential to indirectly affect the warning process in the U.S. during several major severe weather events.
Dense smoke moved northward through the moist sector of another central and southern Plains cyclone in mid May. The smell of the smoke was strong in Norman, OK, on the night of May 14-15, before passage of a dryline the following morning which brought smoke-free air in from the west.
The smoke also cause health hazards for some residents of the central and southern U.S. who had respiratory ailments, according to several public health and air pollution hazard statements sent by NWS offices in south Texas and other areas.