The Environment of Fast- and Slow-Moving Tropical Mesoscale Convective Cloud Lines

Abstract

Rawinsonde data from GATE are composited to examine the environmental similarities and differences between fast-moving (line speed VL > 7 m s−1) and slow-moving VL < 3 m s−1) mesoscale convective cloud lines. Thermodynamic structures for the two types of line are similar with respect to the mixed-layer values of θe and convective available potential energy, but the fast-moving lines have a more pronounced minimum in θe at ∼700 mb. Kinematic structure shows that the vertical shows of the horizontal wind is normal to the leading edge of convention in the fast-moving convective lines but parallel to the leading edge of the slow-moving cloud lines. The results suggest that the type of line (fast versus slow) which forms may be affected by the initial environmental conditions. Abstract Rawinsonde data from GATE are composited to examine the environmental similarities and differences between fast-moving (line speed VL > 7 m s−1) and slow-moving VL < 3 m s−1) mesoscale convective cloud lines. Thermodynamic structures for the two types of line are similar with respect to the mixed-layer values of θe and convective available potential energy, but the fast-moving lines have a more pronounced minimum in θe at ∼700 mb. Kinematic structure shows that the vertical shows of the horizontal wind is normal to the leading edge of convention in the fast-moving convective lines but parallel to the leading edge of the slow-moving cloud lines. The results suggest that the type of line (fast versus slow) which forms may be affected by the initial environmental conditions.