MOISTURE PROFILE Low level moisture is assessed by examining boundary layer dewpoints. Severe thunderstorms are more likely when the surface dewpoint is 55 F or higher, all else being equal. Low dewpoint values inhibit sufficient latent heat release and significantly reduce the tornado threat. Tornadoes are more likely when the LCL is relatively low as compared to relatively high. The depth of moisture in the lower troposphere and the rate of moisture advection are also important to examine. While a lack of moisture in the lower troposphere reduces the severe storm threat, a lack of moisture in the middle troposphere is helpful to the severe storm threat if there is abundant moisture in the lower troposphere. Convective (potential) instability is present in this situation. The advection of higher dew point values into the boundary layer can increase instability in a severe weather situation. This is often accomplished by advection from a warm ocean source. |