Mesoscale Convective Systems

What is an MCS? Usually put into different categories A squall line is one type of MCS A Mesoscale Convective Complex is another type

What is a squall line? Line of thunderstorms, usually in front of a cold front or dry line Most severe type are in front of the cold front Once they form from the cold front, they feed themselves from the gust front of old storms Highest reflectivity occurs on the leading edge See picture on board

What is an mcc? Typically form in calm winds aloft and are driven by the outflow of other storms These move slowly throughout a region, but can grow into huge systems of thunderstorms Highest reflectivity can be embedded in the system Can be best seen on infrared satellite images as a large blob of cold cloud tops

Nighttime systems Both systems typically last throughout the nighttime hours This is due to the nocturnal low level jet which usually forms in the summer months The jet feeds in warm, moist air and forms when winds decouple at night, i.e. an inversion forms Low level jet is strongest around 2-3am

How to forecast squall lines What to look for…. On soundings, look for large amounts of CAPE, however winds will be more oriented in the same direction than they would with supercells On radar, you can often see the rear inflow jet create bowing segments in the squall line, which can sometimes make tornadoes Also, if low level wind shear is present, supercells may form within the squall line

How to forecast mcc Want weaker winds aloft, no upper level jet Still want large amounts of CAPE Low LFC’s when looking at soundings Look in BUFKIT or GARP for the low level jet which can keep storms alive throughout the night