How the destructive hailstorm that hit Austin formed, explained in 3 weather graphics

More than a week after a fast-moving storm tore through Austin, meteorologists have confirmed that a microburst — a rare and intense downdraft — was behind much of the destruction, with winds reaching up to 85 mph in parts of the city.

The May 28 supercell, which rapidly intensified over Austin during peak evening commute, shattered windows, toppled trees and knocked out power to tens of thousands. A new analysis released this week maps the swath of damage and shows how cold air from melting hail fueled sudden, violent downbursts across multiple neighborhoods, according to the National Weather Service.

Area forecast discussions and stormage reports confirm that the microburst formed as several atmospheric systems collided over Central Texas: a stalled front, a humid and unstable air mass and a swirling pocket of mid-level energy known as a mesoscale convective vortex. But it was the rapid cooling from hail aloft — plunging dense air to the surface — that turned the storm especially dangerous.

More: Why did storms hit Austin so hard and fast? A clash of systems from Mexico to Colorado

A storm’s anatomy: What made this one different

A new 3D visualization of the storm’s internal structure illustrates the dynamic system that unfolded between 6:30 and 7 p.m. on May 28. Two distinct downdraft zones emerged during the storm’s peak:

• Rear flank downdraft: This zone moved over downtown Austin with winds of 55 to 75 mph, causing damage to power lines, businesses and trees in the city’s core.

• Forward flank microburst: A stronger blast of wind moved through north, central and east Austin with gusts reaching up to 85 mph. This was responsible for the bulk of the damage, including downed limbs and structural failures.

These powerful downdrafts were supercharged by cold air aloft, created as hail melted and cooled the surrounding atmosphere. The cooled, dense air then rushed toward the surface — a hallmark of a microburst event. Rainfall was also intense, with 2 to 3 inches falling in just 15 minutes in some parts of the city.

At 6:59 p.m., a 77 mph wind gust was recorded at Austin-Bergstrom International Airport, according to the National Weather Service.

How the supercell moved across Central Texas

Radar and satellite data show the storm began forming just after 4:30 p.m. near San Saba and Burnet. By 5:30 p.m., it had intensified and was moving rapidly southeast through Bertram and Liberty Hill. The system reached full strength over Austin between 6:30 and 7 p.m., then weakened slightly as it continued into Bastrop County by 8 p.m.

High-resolution radar reflectivity maps show intense precipitation and hail cores as the storm moved. Overlaid warning polygons issued by the National Weather Service show how forecasters tracked its growing intensity in real-time, though even advanced models struggled to predict its sudden severity.

Mapping the destruction

A detailed damage map compiled from 311 reports, radar scans, storm surveys and public submissions highlights the storm’s impact zones:

• Red zone (forward flank microburst): Covers large swaths of north and east Austin, where peak winds and destruction were concentrated.

• Yellow zone (rear flank downdraft): A slightly weaker path over downtown, still capable of widespread damage, broken windows and uprooted trees.

The wind swaths largely followed major transportation corridors, including I-35, US-183, and FM 969, highlighting just how widespread and structured the damage path was.

This article originally appeared on Austin American-Statesman: Inside the microburst that hit Austin, explained in 3 NWS graphics