![]() ![]() As a result, there is precipitation seen falling within the rear-flank and forward-flank downdrafts. While it may be slightly difficult to discern the rear-flank and forward-flank downdrafts from the photograph above, the Doppler radar image below gives a clear visual of the distribution of precipitation. Unlike LP supercells, the removal of precipitation mass from the updraft is not as significant. A classic supercell north of Leoti, Kansas, on May 21st, 2016. ![]() These types of supercells can be coined as the “Goldie Locks” of supercells such that there is not too much precipitation that falls out of the downdraft to obscure the mesoscale features involved with the storm. They often produce large hail given strong mechanical forcing or high values of CAPE, and can sometimes produce tornadoes if the environment is not too dry.Ĭlassic supercells often occur in an environment where the upper-level storm-relative winds are between 40-60 knots. Typically, LP supercells have elevated bases for a multitude of reasons including a high shear and low CAPE environment, or a rather dry environment with weak wind shear and high CAPE. However, you will also see that the upper-level storm-relative winds were roughly 60 knots on the evening of March 7th, which meant LP supercells were likely. While the Convective Available Potential Energy, or CAPE, is sufficient for thunderstorms, the wind shear was important to analyze as the bulk wind from the ground to the mid-levels of the storm were averaged at about 40 knots - which is more than conducive for a supercell despite the rather weak CAPE in place. In the sounding profile above, you will notice that the thermal instability is roughly 1,300 J/kg. The 6:00pm CST observed sounding from Norman, Oklahoma, on March 7th, 2016. Below was the observed sounding profile from that evening from a weather balloon that was launched from the National Weather Service in Norman, Oklahoma. Notice that the base of the supercell is not obscured by any precipitation and that the majority of the precipitation is being “flung” to the northeast, or to the right of the image. LP supercell east of Coldwater, Kansas, on March 7th, 2016. This is visualized through the excessive tilting of the updraft, with a barber pole like structure to the supercell. It is clearly evident in the photo above that the upper-level storm-relative winds are quite strong. A low-precipitation supercell near Coldwater, Kansas, on March 7th, 2016. ![]() Thus, very little precipitation is left to fall out of the base of the storm. ![]() This is due to the strong winds in the upper levels of the storm that can evacuate the mass flux of precipitation far away from the updraft. Low-precipitation supercells can occur if the upper-level storm-relative winds are ≥60 knots. The stronger the storm-relative winds, the greater the likelihood that vertical wind shear will increase as well. Strong winds moving into a storm can generate an increase in storm-relative helicity as well, which can enhance the potential for tornadoes. Storm-relative winds are important to analyze in a severe weather environment since they can allow a storm to ingest energy and moisture by taking advantage of the air within the inflow layer regions of the storm (the layer where air flows into the supercell’s updraft). Detailed information about the storm-relative wind can be found in this scientific journal. A corollary for the storm-relative wind can be thought of as viewing an object in motion while in a vehicle, versus watching a vehicle pass you by as you stand on the ground. While there are many contributing factors that revolve around determining the storm mode of a supercell, one of the most important factors is analyzing the storm-relative wind, particularly in the upper levels (or anvil level) of the supercell. A supercell near Sayre, Oklahoma, on May 16th, 2015. The configuration of the wind shear profiles within a severe weather environment is critical in diagnosing what types of supercells can be expected on a given day. There are three types of supercells: low-precipitation (LP), classic, and high-precipitation (HP). A supercell is a thunderstorm that rotates. Determining the type of supercells that may occur within a given severe weather environment is important for a multitude of reasons. ![]()
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