From a Pyrocumulus to a Severe Thunderstorm: An Environmental Analysis of an Anomalous Southern Plains Wildfire

A rare pyrocumulonimbus (pyroCb) formed over the 30,566 hectares (ha) Mallard Fire in the Texas Panhandle on 11 May 2018, later becoming a severe thunderstorm that produced 2.5 cm hail 155 km east of Amarillo, TX. This is the second documented instance of a pyroCb-severe thunderstorm evolution on the Great Plains, where the previous was with the Jasper Fire in South Dakota on 27 August 2000. Recent improvements in remote sensing (e.g. GOES-16) allowed unprecedented observation of this highly anomalous transition. A pyroCb typically forms over a wildland fire in an unstable environment with a relatively deep and dry boundary layer characterized by dry-adiabatic temperature lapse rates and constant mixing ratio. Extreme fire conditions combined with the local terrain and an unstable environment supported pyrocumulus (pyroCu) along the dryline. By the afternoon, the pyroCu matured into a pyroCb just east of the dryline in the eastern Texas Panhandle. Mixed layer convective available potential energy values of 2000-2500 J kg-1 and effective bulk wind shear of 15-20 m s-1 supported an environment conducive for sustained convection and potential severe storm development. Given the complex, non-linear wildfire-atmosphere interactions, it is difficult to predict severe pyroCb development. This study will utilize GOES-16 satellite imagery and WSR-88D observations to examine the transition from pyroCu to a severe thunderstorm. Additionally, analysis will demonstrate the real-time Impact-Based Decision Support Services between the Amarillo National Weather Service, core partners, and the general public. The main objective is to discuss the atmospheric, fuel, and terrain considerations associated with the Mallard Fire severe pyroCb.

Photos

(Photo Credit: Fire Specialist James Buhrkuhl Austin Fire Department)	(Photo Credit: Two for the Road)	(Photo Credit: Trent Hoffeditz)	(Photo Credit: Mike Umscheid)

(Photo Credit: Matthew Cappucci)	(Photo Credit: Matthew Cappucci)	(Photo Credit: NWS Southern Region HQ IMET)	(Photo Credit: Andrew Bivins)

(Photo Credit: Andrew Bivins)	(Photo Credit: Andrew Bivins)	(Photo Credit: Andrew Bivins)

Fuels

Drought Monitor	Brush (2 feet)	Juniper, Mesquite and Cedar	Tall Grass (2.5 feet)

Fire Behavior Triangle	Energy Release Component (ERC)	Texas Tech Real-time WRF Red Flag Threat	Southern Great Plains Wildfire Outbreak (SGPWO) Outlook

Observed 100-hour Fuel Moisture	Observed Fire Danger Class

Environment

12z Amarillo Sounding	00z Amarillo Sounding	0-Hour HRRR MLCAPE (Shaded, J/kg) and 0-6 km Shear (barbs, knots) with Level II Radar Reflectivity (dBZ) overlayed

0-Hour HRRR Dewpoint (shaded, Fahrenheit), Surface Relative Humidity (brown contours, percent) and Surface Pressure (black contour, millibars)	RAP 850mb Heights (white contour, millibars), 850mb Temperatures (shaded, Celsius) and Winds (barbs, knots)	500mb Heights (black contour, millibars), 500mb Temperatures (red dashed, Celsius) and Winds (barbs and shaded, knots)

Outlooks

1200z Storm Prediction Center (SPC) Fire Outlook	1430z Storm Prediction Center (SPC) Categorical Outlook	Storm Prediction Center (SPC) Mesoscale Discussion

National Weather Service Messaging

NWS Amarillo Graphic	Hot Spot Notification Tool May 10, 2018	Hot Spot Notification Tool May 12, 2018	Hot Spot Notification Tool May 14, 2018

Fire Danger Statement (RFD)	NWS Amarillo Chatroom May 11, 2018

NWS Amarillo Chatroom May 12, 2018	NWS Amarillo Chatroom May 13, 2018

Results & Analysis

Storm Reports	5 Minute Total ENTLN 1 Minute Update Lightning (5 km grid)	Radar Reflectivity and Total Cloud Flashes

GOES16 Cloud Top Phase IR Band and ENTLN 5 km grid with 5 minute total flash density (1 minute updates)	GOES16 Visible Satellite and GOES16 Fire Temperature

NLDN Cloud to Ground and Intra-Cloud Pulse Data for 20z May 11, 2018 to 00z May 12, 2018 (Photo Credit: Chris Vagasky)	West Texas Lightning Mapping Array (LMA)