this shows as clear notches where one can find stronger downdrafts at the surface. These kinds of lines often have a very characteristic undulating pattern caused by the interference of the gusts fronts coming from different parts of the line. Finally, in any type of thunderstorm, the surface cold pool of air associated with the downdraft will stabilize the air and form a cloud-free area that will end along the gust front. This mesoscale front, when moving into a warm and unstable air mass, will lift it and cumulus clouds appear on satellite pictures. This line is likely the point of further convection and storms, especially if it coincides with fronts from other thunderstorms in the vicinity. One can notice it at the leading edge of a squall line, in the southeastern quadrant of a typical supercell (in the northern hemisphere), or different regions around other thunderstorms. They may also be visible as an outflow boundary hours or days after convection and can pinpoint areas of favored thunderstorm development, the possible direction of movement, and even likelihood for tornadoes. The speed of forward movement of the outflow boundary or gust front to some degree modulates the likelihood of tornadoes and helps determine whether a storm will be enhanced by its presence or the inflow be choked off thus weakening and possibly killing the storm. Thunderstorms may move along slow-moving or stationary outflow boundaries and tornadoes are more likely; whereas fast-moving gust fronts in many cases weaken thunderstorms after impact and are less likely to produce tornadoes—although brief tornadoes may occur at the time of impact. Fast-moving gust fronts may eventually decelerate and become slow-moving or stationary outflow boundaries with the characteristic "agitated area" of cumulus fields previously mentioned. Lightning detection Usually in conjunction with data sources such as weather radar and satellites, lightning detection systems are sometimes utilized to pinpoint where thunderstorms are occurring (and to identify lightning hazard). Currently, most lightning data provided in real-time is from terrestrial sources, specifically, networks of ground-based sensors, although airborne sensors are also in operation. Most of these only provide latitude & longitude, time, and polarity of cloud-to-ground strikes within a limited range. Increasing in sophistication and availability, and affording data for a very wide area, are satellite-based lightning detectors which initially included optical sensors indicating flash rates and horizontal location but now radio frequency receivers that can identify intra-cloud flashes with the