FORT WORTH, Texas — The supercell storms tracking through the Dallas-Fort Worth corridor Tuesday afternoon are not behaving like classic tornado producers — and the atmospheric science behind today’s setup explains exactly why. These are High Precipitation supercells, commonly called HP supercells or meteorological meatballs, characterized by extreme rainfall output with large hail cores embedded deep within the rain shield. The combination of abundant warm moisture, parallel bulk shear and strong storm-relative inflow is producing storms that are big time rain makers with hail that is difficult to see coming until it is already falling.
Why These Storms Are HP Supercells — Not Classic Hail Producers
Two specific atmospheric factors are driving the HP character of today’s storms, and both are visible in the HRRR sounding analysis valid Tuesday April 28 at 22Z for the 32.73°N, 97.09°W location near the Fort Worth corridor.
Factor One — Extreme Low-Level Moisture: The sounding shows the atmosphere is very saturated with moisture and large mixing ratios through the lowest levels. The parcel path does not reach freezing until nearly 6 km into the atmosphere — an extraordinarily high freezing level for hail production. That much warmth and lift in the lower half of the storm generates a large amount of rainfall before any precipitation reaches hail-producing temperatures. The DCAPE of 1442 and surface dewpoints near 79°F confirm the depth and richness of the moisture being ingested into these storms.
The sounding also shows very large CAPE between 0°C and -20°C — the Hail Growth Zone — with large CAPE and ice and supercooled water extending into the upper levels. This is the hail-producing layer, but it sits on top of the deep warm moisture layer below, meaning storms must first process enormous amounts of warm rain before hailstones can grow and survive long enough to reach the ground…