Cumulonimbus approaching the troposphere (fuzzy top).
Within a 5 minute period, these cumulus cloud clusters transitioned to towering cumulus (cumulus congestus) and then grew into a large cumulonimbus cloud mass that produced lightning and rain. They formed so quickly that they dissipated within another 10 minutes.
Some mammatus clouds associated with a cumulonimbus cloud (thunderstorm). As seen in south central Florida during a moderate thunderstorm. No reports of tornadic activity and lightning strikes were only occasional. Since this was observed in late March, the freezing level was probably around 12,000 feet or so. Lightning normally occurs whenever the top of a cumulonimbus cloud reaches at least 10,000 feet above the freezing level. So the top of this cell was around 22,000 to 25,000 feet – not likely a severe weather event producer as it was nearly stationary and not associated with a front. Contrast that with the atmosphere during the summer – a thunderstorm cell in this area would reach 50,000 feet or more and be more likely to produce severe weather.