The Above-Anvil Cirrus Plume Signature: The Most Definitive Indicator of a Severe Deep Convective Storm within Visible and Infrared Satellite Imagery

Intense convective storms have adverse impacts on people, property, and infrastructure through the hazardous weather they generate. Gravity wave breaking atop intense tropopause-penetrating updrafts can lead to irreversible detrainment and lofting of ice into the stratosphere in the form of cirrus plumes that can reside several kilometers above the primary anvil. Given that they reside in the stratosphere where temperatures are warmer than the primary anvil cloud in the upper troposphere, these above anvil cirrus plumes (AACP) appear anomalously warm in satellite infrared (IR) imagery. The presence of a warm area emanating away from the extremely cold updraft, also known as an overshooting top (OT), bounded by much colder anvil (up to 20 K) produces a V- or ring-like appearance in IR imagery. This has led to AACP being referred to in the literature as “enhanced-V” or “cold-ring” signature. These signatures and their connection to severe weather have been noted for over 30 years, but advances in satellite imager spatial and temporal resolution and ground-based radar products has shed new light on their formation and connection to severe weather.

For example, significant severe weather outbreaks can feature dozens of AACP storms across extensive geographic regions, and AACPs have been found above convection throughout the globe. AACPs were present within ~75% of the most significant severe storms observed by GOES from 2010-2015 across the US, those that generated 4.5+ inch hail, 90+ mph wind, and/or an EF4+ tornado (n=245 cases). Using 1-min GOES-14 super-rapid scan observation (SRSO) imagery, research has shown that ~60% of AACP storms present across several SRSO days were severe and the initial emergence of an AACP occurred on average 18 minutes prior to a report of severe weather (1+ inch hail, 58+ mph wind, and/or tornado). Tropopause-penetrating updrafts, commonly referred to as overshooting tops (OTs), are quite common in deep convection and especially evident and ubiquitous in GOES 30-60 SRSO imagery. But perhaps only 1% of OT-producing storms are severe compared to 60% of AACP storms. This leads us to believe that an AACP is the strongest indicator of a severe storm in satellite imagery documented to date and early recognition of an AACP could help improve warning lead time and/or confidence.

This presentation will highlight recent NASA-sponsored research on severe convection and AACP storms that helps to explain 1) the conditions favorable for AACP storms, 2) storm characteristics in radar, satellite, and lightning imagery/products before, during, and after AACP generation, and 3) AACP relationship with severe weather, taking advantage of GOES-14 and -16 super-rapid scan imagery to define AACP lifetimes as precisely as possible.