Tag Archives: bears cage

More April, 2011 Supercells in TX & AR

In this post, I’ve included a variety of supercell structures from more than one location. Regardless of the locale, each of these storms presented a significant threat to life and property.

In our first image, we have a supercell scanned from the Dyess AFB, TX doppler radar (KDYX) at 0238 UTC on 24 April 2011. A very clean inflow notch and hook echo can be seen.

The Storm Relative Velocity (SRV) product shows a very strong couplet indicating vigorous rotation with the storm. It’s very likely that a tornado was forming or already in progress.

This Base Reflectivity (BR) product is a supercell scanned from the Fort Worth, TX doppler radar (KFWS) at 2045 UTC on 25 April 2011. The image shows more of the classic supercell structure with a textbook hook echo a few miles south of Cleburne, TX. A tornado was reported at the time of the BR scan.

The above SRV scan is from a supercell near Little Rock, AR (KLZK) on 26 April 2011 at 0006 UTC. A very strong couplet can be seen near Mayflower, AR along with a strong Rear Flank Downdraft (RFD) passing over Maumelle, AR. At the time of this scan, a tornado was in progress.

The storms during this event were moving very rapidly, almost 50 mph. As you can see in this BR scan, the center of circulation has moved northeast of Mayflower, AR in just nine minutes. A large tornado was reported and the purple reflectivity is indicative of a substantial amount of airborne debris. This is often referred to as a “debris ball.”

The SRV product from KLZK at the same time as the above BV image shows a well defined couplet. Just south of the couplet is a hint of a RFD and/or gust front associated with the storm just to the south.

Approximately one hour later, the storms had consolidated into more of a linear structure. North of the KLZK radar site, a “comma head” echo had taken shape. This is frequently seen at the northern part of a particularly intense squall line. The northern portion of the storm structure begins to wrap around itself and almost becomes a mesoscale low pressure area. It’s also not uncommon for tornadoes to occur in this region.

As displayed by the KZLK SRV scan at 0124 UTC, a broad area of rotation exists with the comma head echo. This is especially evident by the strong inbound (green) winds. A substantial bow echo has also developed to the south.

During the afternoon of the same day, storms redeveloped over portions of AR including this supercell observed by the Fort Smith, AR doppler radar (KSRX) which, in the BR scan, shows an unusual circle in the mesocyclone. This is likely a result of a very heavy rain curtain being drawn around the south side of the mesocyclone creating what storm chasers refer to as a “bears cage.” A tornado was reported with this storm at the time of this scan.

The KSRX SRV scan at the same time shows a significant couplet. A confirmed tornado was in progress at the time of the scan. The inflow winds on the couplet are particularly strong.

Later that evening at 2307 UTC, a supercell with strong rotation approached the Memphis, TN metro as seen in this BV product from the KNQA doppler radar. This image shows structure that is more characteristic of a High Precipitation (HP) supercell. HP supercells can be particularly dangerous since they often hide the tornado in very heavy rain. The location of the mesocyclone circulation would be just a few miles southwest of Marion, AR.

As we can see from the KNQA SRV product at 2311 UTC, the advantage of doppler radar is obvious. A very strong couplet can be observed just southwest of Marion, AR moving to the northeast. By just using visual observations, the area of rotation would likely have been obscured or impossible to see due to the heavy precipitation wrapped around the mesocyclone. Damage was reported with this storm, but was very minor compared to the record breaking outbreak that would occur the next day.

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