This week is Severe Weather Awareness Week for Nebraska, which is a time for us to brush up on our severe weather preparedness. No better way to be prepared than knowing the thunderstorm will eventually become a main weather concern.
Many times, during the thunderstorm season, you will hear the term “supercell thunderstorm”. Supercells can grow to be monsters, producing grapefruit size hail and tornadoes with winds over 200 mph. These thunderstorms can also dump inches of rain in less than an hour and generate 90 mph straight line winds. Supercells contain what is called a mesocyclone and long-lasting rotating updrafts. There are three types of supercell storms. The first is known as the LP supercell or low precipitation thunderstorms.
These storms do not produce a lot of rain, but hail and tornadoes are still possible. Storm chasers love the LP supercell because they can see all the characteristics of a tornadic thunderstorm, from the wall cloud, to the funnel and finally the tornado itself. The classic supercell has a strong updraft and a flanking line extending from the storm. Usually, more moisture is available and hail and heavy rain is likely. LP and classic supercell storms are most common in western Nebraska. The final type of supercell is the HP or high precipitation supercell.
These storms can produce very heavy rain in a short period of time, which can produce flash flooding. Another danger with HP supercells is that there is so much rain that it can hide the tornado. The tornado becomes rain wrapped and people cannot visually see the tornado until it is right in front of them.