Initiation to Dissipation -- Smithville, MS Tornadic Supercell

I'll be starting a new series on this blog called Initiation to Dissipation. I'll be using radar images from the historic April 27 tornado outbreak to show the life cycle of some of the worst tornadic supercells and some of the most impressive signatures during their life cycles. The first supercell featured will be the one that produced an EF-5 tornado in Smithville, MS.


Convective initiation of this supercell began around 1643Z in Northeast Louisiana near Rayville.


Over the course of the next hour, this storm strengthened and began to develop a weak mesocyclone. Within the storm's first hour, it initially had a difficult time time separating itself from other convection. It's possible that hodographs were not as strongly curved in the lowest three kilometers, thereby making deep layer shear vectors more parallel to the pre-frontal trough that the storms initiated along.


By 1843Z, however, hodographs appeared to become increasingly favorable for semi-discrete supercells. In fact, the storm had clearly became separated from other convection and even had unimpeded inflow into the updraft region. Weak supercell characteristics were seen by this time with as a weak echo region (WER) was present along with a weak, persistent mesocyclone.


An hour later, the supercell appeared to be entering its mature stage. Distinct supercell characteristics were noted, including the presence of a WER, a bounded weak echo region (BWER), a strong mesocyclone, and a hook echo.


By 2042Z, the supercell is located near Smithville and likely near its peak intensity. A very tight concave reflectivity gradient is present in the inflow region of the supercell, a very impressive WER and BWER were also present, a hook echo persisted, and a very strong low and mid-level mesocyclone were still present.





A zoomed in image of the supercell west of Smithville (left) shows an impressive BWER at around 9,300 feet. As the supercell moved northeast of Smithville, a tornado signature can be seen in the storm relative motion data along with a very high normalized rotation (NROT) value typically only seen in intense mesocyclones and tornadoes.


By 2142Z, another cell had merged with the supercell and seemed to interfere with its structure. Nonetheless, a strong mesocyclone remained present along with a WER.


The supercell remains in tact another hour later, but it's clearly not as well-defined as it once was over Northeast Mississippi. It also becomes apparent that convection to its south may likely further disrupt the updraft.


Indeed, by 2343Z, the storm has weakened considerably and shows no signs of supercell characteristics.


By 00Z, the storm had pretty much dissipated but not before traveling a total of about 437 miles!

Damage Survey Images

Scenes and Thoughts From Tuscaloosa

One of the worst tornado outbreaks in United States history occurred on Wednesday, April 27, 2011. 134 tornadoes have been confirmed (as of May 9) across 17 states with Alabama being the hardest hit. During a 24-hour period from 8 a.m. on April 27 to 8 a.m. on April 28, 309 people were killed, including 236 in Alabama.

Why did so many people die? I believe this article does an excellent job of providing many answers. Many folks in the meteorology community may disagree with me, but I don't think there's a lot to be learned from this event from a scientific meteorological perspective. It was extremely well forecast by the Storm Prediction Center and local Weather Forecast Offices up to five days in advance. However, I think there is a tremendous amount that we can and will learn about societal impacts from this tornado outbreak.

Arguably, the most recognizable tornado from this outbreak was the Tuscaloosa-Birmingham tornado. This tornado was rated an EF-4, it produced a continuous damage path for 80.3 miles, and it killed 65 people. It is the single deadliest tornado since May 25, 1955. Tuscaloosa was particularly hard hit where 41 fatalities occurred. A few days after the tornado, I traveled to Tuscaloosa to help out my mom and sister who were hit by the tornado and to get a firsthand view of the destruction. I witnessed the damage from the F4 tornado in Tuscaloosa on December 16, 2000, and I can attest that the magnitude and spatial extent of this damage was much worse.


The aerial image above shows the damage and devastation in the Forest Lake neighborhood associated with the April 27 tornado in Tuscaloosa. The numbers on the aerial image indicate where ground-level images were taken on April 30.


Image 1 was taken at 19th Street East and included a miracle story of survival. The house in the foreground was a single-level home with a basement. The house was completely destroyed with much of the rubble collapsing in the basement. The homeowner was an elderly woman that sought shelter in the basement, only to have her house collapse on top of her. After the tornado passed, a few students living across the street pulled the woman out of the wreckage. She sustained only minor injuries.


Image 2 is looking across Forest Lake at heavily damaged and destroyed homes along Forest Lake Drive where EF-4 damage occurred. Trees were also snapped, debarked, and thrown into the lake. Other debris in the lake included a refrigerator and a basketball goal.


Image 3 was taken near 1st Avenue and Fernwood Court. Part of a metal roof from University Place School was found twisted around a tree.

It's events like this that are the driving motivator of my career. Fortunately, I've never worked an event where lives have been lost, but I realize that won't be the case forever. However, after hearing the horror that my family went through and seeing many of my great childhood memories reduced to rubble, I have an even greater appreciation for my job as a warning forecaster.

Despite the circumstances in Tuscaloosa, I have complete confidence that the city will rebuild better than ever. I will be forever amazed at the amount of support and unity that I witnessed -- it was truly inspiring. If you feel compelled to help tornado victims, you can donate to the American Red Cross.

Vilonia, Arkansas Tornado

The atmosphere continues to unleash wave after wave of severe weather outbreaks. Since April 9, there have been eight days in which significant tornadoes have occurred. This evening added to that total as a long track tornadic supercell plowed across towns northwest of Little Rock. The hardest hit location appears to be the town of Vilonia. According to early police reports, the town of Vilonia is "gone". The radar image below is the 0.5 degree cut, which sampled this tornadic supercell at 800 feet above ground level.

This is one of the most impressive tornado signatures I've seen on base radar data. The SRM (using a storm motion vector of 232 degrees and 39 kt) indicated a maximum inbound velocity of 81.6 kt with a maximum outbound velocity 87.4 kt. The base reflectivity showed a debris ball signature along with very high spectrum width values collocated within the debris ball. These signatures give radar operators a high degree of confidence that a tornado is occurring.

St. Louis Struck by Tornado

A very active severe weather month continued today across the southern Plains and mid-Mississippi Valley. As of this posting, there have been 194 severe weather reports, including 13 reports of tornadoes. The most significant tornado appears to have occurred in the St. Louis metro area this evening. Below is a four-panel radar image (0.5 deg) of a tornadic supercell moving across the northwest side of St. Louis around 8:03 p.m.


The top left panel is base reflectivity, the top right panel is base velocity, the bottom left panel is storm relative motion, and the bottom right panel is spectrum width. X marks the spot of Lambert-St. Louis International Airport. Three minutes after this radar image, the FAA weather observer reported a tornado visible from the airport. Here is the full METAR:
KSTL 230111Z 29022G34KT 240V310 3SM +FC -TSRA FEW020 BKN050CB OVC090 22/19 TORNADO B10 W MOV E AO2 PK WND 29034/0111 CONS LTGICCGCC ALQDS TS ALQDS MOV E P0001

May 10-11 Chases

I had a couple of off days on Monday and Tuesday, so I took the opportunity to take a mini chase vacation with my buddies Michael Carter, Greg Nordstrom, and Tim Wallace. Fortunately, the weather pattern was very cooperative from a chasing standpoint, and we all felt confident about a powerful western U.S. trough impacting the southern Plains more than a week and a half before the event. Unfortunately, damage, injuries, and fatalities occurred as a result of the May 10 tornadoes across Central Oklahoma. As part of a quick recap, I've compiled some video, links, and damage surveys from the wedge tornado we came within at least 200 yards of near Cromwell, OK.

VIDEOS

Video by Greg Nordstrom

Video by Michael Carter

May 10, 2010 Tornado Outbreak -- WFO Norman

May 10, 2010 Severe Storms and Tornadoes -- WFO Tulsa

CIMSS Satellite Perspective

Michael Carter's Chase Summary

STORM SURVEYS

-From WFO Norman-
...TECUMSEH TO CROMWELL AND POINTS EAST TORNADO...

RATING: EF-3
MAX WIDTH: 3/4 TO 1 MILE
PATH LENGTH: AT LEAST 30 MILES ONLY COUNTING NWS NORMAN PORTION
BEGIN POINT: ABOUT 2.8 WSW TECUMSEH
END POINT: CONTINUED INTO NWS TULSA AREA ABOUT 0.8 E CROMWELL

THIS LONG TRACK TORNADO MOVED FROM POTTAWATOMIE COUNTY INTO SEMINOLE COUNTY...AND THEN CROSSED INTO OKFUSKEE COUNTY WHICH IS IN THE NWS TULSA COUNTY WARNING AREA. THE TORNADO CAUSED SIGNIFICANT DAMAGE ALONG THE ENTIRE TRACK...WITH NO NOTABLE GAPS IN DAMAGE ALONG THE LENGTH OF THE PATH SURVEYED. AT TIMES...THE DAMAGE FIELD WIDENED TO ABOUT 3/4 OF A MILE WIDE...POSSIBLY UP TO 1 MILE WIDE. THE MOST INTENSE DAMAGE SEEMED TO BE JUST NORTH AND NORTHEAST OF EARLSBORO NEAR THE POTTAWATOMIE-SEMINOLE COUNTY BORDER. IT WAS IN THIS LOCATION THAT A 5 BEDROOM...2 STORY FOUNDATION HOUSE WAS DESTROYED EXCEPT FOR SEVERAL INTERIOR WALLS NEAR THE BATHROOM. IN THIS SAME VICINITY...A PICKUP TRUCK APPEARED TO HAVE BEEN LOFTED FOR ABOUT 1/4 MILE...AND A SEMI TRAILER WAS ROLLED OR LOFTED FOR A FEW HUNDRED YARDS. BOTH OF THESE LARGE MISSILES WERE DRAWN FROM THE NORTHERN HALF OF THE DAMAGE PATH TOWARDS THE CENTER. A LITTLE FURTHER EAST...7 HIGH TENSION TOWERS WERE DOWNED. ALONG THE ENTIRE PATH...TREE DAMAGE WAS NOTED...AND A FEW TREES WERE DEBARKED AND STRIPPED OF ALL THEIR BRANCHES.


-From WFO Tulsa-
A TORNADO THAT MOVED ACROSS PORTIONS OF NORTHERN HUGHES COUNTY...INCLUDING THE TOWN OF CROMWELL...CROSSED INTO SOUTHWESTERN OKFUSKEE COUNTY 3 MILES WEST OF BEARDEN AT ABOUT 635 PM CDT. THE TORNADO MOVED NORTHEAST AND DISSIPATED JUST SOUTH OF I-40 ABOUT 3 MILES NORTH OF BEARDEN AT ABOUT 647 PM CDT. MANY TREES WERE DAMAGED IN THE PATH...WHICH WAS ABOUT 5 MILES LONG AND HAD A MAXIMUM WIDTH OF 400 YARDS. BASED ON THE TREE DAMAGE...THE TORNADO WAS RATED EF-1 ON THE ENHANCED FUJITA SCALE WITH MAXIMUM WIND OF UP TO 95 MPH.

MAY 11
This day proved to be a lot quieter than May 10, but one dominant supercell did develop ahead of the triple point across Northwest Oklahoma. After a couple of rounds of deep moist convection failed to sustain itself, likely due to a capping inversion, one LP supercell developed near Crawford, OK just after 6:30 p.m. The supercell slowly moved to the northeast, produced significant hail southwest of Woodward, and eventually dissipated near Freedom, OK. The laminar nature of the storm's base prevented this from being a tornado threat, but hordes of chasers were treated to a beautiful spectacle at sunset.

Video by Greg Nordstrom

Satellite Perspective of April 24 Tornado Outbreak

CIMSS has put together a very good satellite analysis of the April 24, 2010 tornado outbreak across the Deep South. A few MODIS images are included at the bottom of the recap, which show the tornado scar left in the wake of the Yazoo City tornado.

CIMSS - Deadly tornado outbreak across the Deep South

Yazoo City Tornado Chase Accounts

I've linked a couple of worthwhile storm chase accounts about the preliminarily rated EF3 tornado in Yazoo City, MS on April 24, 2010. Two of my good buddies, Greg Nordstrom and Michael Carter, provide some insight into the synoptic and mesoscale setup for yesterday's tornado outbreak and discuss issues related to storm chasing in the Deep South.

Greg Nordstrom's Chase Recap

Michael Carter's Chase Recap