Fall 2016 – Spring 2017

VORTEX-SE Spring 2017 Experiment Field Catalog

Data Catalog

28 November 2016

Event summary: Sub-severe QLCS in Alabama that produced wind damage in Mississippi.

Deployment summary: UAH deployed assets across N-central Alabama to sample the QLCS.

Manuscripts and presentations related to this case:

Conrad and Knupp 2019 (MWR): Investigates horizontal shearing instability along the gust fronts of HSLC QLCSs. 28 November serves as the non-tornadic case.

29-30 November 2016

Event summary: Major tornado outbreak from the early evening of 29 November through the pre-dawn hours of 30 November centered on NE Alabama, extending southwestward to E-central Mississippi and northeastward into S East Tennessee. Corridor outbreak comprising primarily of numerous very long-lived, cyclic, classic supercells that followed nearly similar tracks to one another, leading to training of supercells and instances of parallel tornado tracks in close proximity, including five separate tornadoes from four different parent storms in Jackson County, AL, alone. Supercell initiation began mid-late afternoon on the 29th in central and E Mississippi. Several of these supercells traveled northeast for several hours across north Alabama and into far NW Georgia and S East Tennessee. EF2+ tornado activity was mostly concentrated across N-central and NE Alabama, with a couple additional significant tornadoes in East Tennessee and one in NW Alabama. Six fatalities were recorded, four from an EF3 tornado in NE Alabama and two from another EF3 east of Chattanooga.

Deployment summary: This was the first full deployment conducted by UAH to study the Sand Mountain plateau region of NE Alabama during a severe weather event. All UAH mobile assets except for the MIPS were deployed to areas atop Sand Mountain or within the Tennessee Valley. The MoDLS (Doppler wind lidar) system experience four supercell mesocyclone passages within 10 km of its site, approximately 7 km SW of Scottsboro, Alabama. The MIPS system, which remained at UAH, directly sampled the overhead passage of a large (~11 km semi-major axis diameter) mesocyclone approximately five minutes prior to genesis of an EF2 tornado atop Monte Sano, on the east side of Huntsville.

17-18 December 2016

Event summary: Surging arctic anafront led to development of mostly post-frontal squall line that moved across Mississippi, Alabama, and Tennessee. Development of cells immediately along the front resulted in the development of a few tornadoes, including a pair of EF0 tornadoes in far NW Alabama.

Deployment summary: UAH conducted limited mobile operations across N-central Alabama and far S Middle Tennessee to capture the passage of the squall line.

22 January 2017

Event summary: Long-lived outbreak of 70 tornadoes from the pre-dawn hours of 20 January through the evening of 22 January. Five separate waves of tornadic storms occurred along and south of I-20 in Louisiana, Mississippi, Alabama, N Florida, and the Low Country of South Carolina. The first wave began with a discrete supercell producing a long-tracked EF3 tornado that caused severe damage and four fatalities in Hattiesburg, Mississippi, during the predawn hours of 20 January. This supercell and surrounding convection grew upscale into a QLCS that produced numerous tornadoes from the early morning through mid-afternoon hours of 21 January across central and S Alabama and Georgia and into the Low Country of South Carolina. As this QLCS slowly weakened, new supercells formed in N Louisiana, initiating the second round of tornadoes. These supercells grew upscale into another QLCS that produced wind damage and isolated tornadoes across central Mississippi and Alabama during the late evening and overnight hours of 21-22 January. As that QLCS progressed, the third wave of tornadoes occurred across SW Georgia during the pre-dawn hours of 22 January as isolated discrete supercells moved ashore along the central Florida panhandle coast. One of these tornadoes caused EF3 damage at Adel, Georgia, killing 11 people. The final wave of tornadoes occurred during the afternoon hours of 22 January across SE Alabama, S Georgia, and N Florida. The largest and strongest tornado of the outbreak occurred during this wave at Albany, Georgia, killing five people. The tornado was rated EF3, had a path length of 70 mi., and a maximum path width of 1.5 mi.

Deployment summary: Storm survey teams from UNC-Asheville and University of Georgia surveyed the damage associated with the Adel and Albany, Georgia, EF3 tornadoes.

8 February 2017

Event summary: A few weak supercells occurred across North Alabama. A sub-tornadic vortex damage track was found south of Priceville, Alabama, with peak estimated winds around 60 MPH.

Deployment summary: UAH assets were deployed to the Sand Mountain vicinity in NE Alabama.

24 February 2017

Event summary: Mostly sub-severe multicellular convection, with one severe-warned storm in S Middle Tennessee.

Deployment summary: UAH assets were deployed to the Sand Mountain vicinity.

1 March 2017

Event summary: Numerous supercells developed across north Alabama along a cold front. The supercells remained slight elevated above their collective outflow cold pool and remained non-tornadic. Widespread severe hail was observed across north Alabama.

Deployment summary: UAH assets were deployed to the Sand Mountain vicinity.

9 March 2017

Event summary: A severe QLCS moved SE out of Missouri and Kentucky into Tennessee and north Alabama. Rapid changes in the low-level moisture and wind profiles were observed ahead of the QLCS arrival. An EF1 tornado was confirmed near Estill Springs, Tennessee.

Deployment summary: Limited profiling and sounding operations were performed on the UAH campus.

21 March 2017 – VSE Spring 2017 Experiment Shakedown

Event summary: High-LCL QLCS event on VORTEX-SE Spring 2017 Media Day. Wind damage occurred across S Middle Tennessee and far NE Alabama.

Deployment summary: A limited number of assets deployed in NE Alabama ahead of the QLCS.

25 March 2017 – VSE Spring 2017 Experiment IOP1A

Event summary: A generally sub-severe QLCS moved across north Alabama. A few weak mesovortices were observed by mobile radar assets, and isolated sub-EF0 wind damage was reported.

Deployment summary: Full-scale VSE deployment of assets across NW and N-central Alabama (Spring 2017 “western domain”).

27 March 2017 – VSE Spring 2017 Experiment IOP1B

Event summary: Two waves of widespread severe weather occurred across north Alabama: an afternoon wave of supercells followed by a bow echo. Severe-criteria wind and hail occurred with both rounds of convection. Low-level SRH was fairly small, and no tornadoes were observed (although a couple tornado warnings were issued with the supercells).

Deployment summary: Full Spring 2017 western domain deployment.

30 March 2017 – VSE Spring 2017 Experiment IOP2

Event summary: Coastal convective complex disrupted moisture return and low-level mass fields across north Alabama, leading to only weak convection occurring.

Deployment summary: Most assets were deployed to the Sand Mountain vicinity (Spring 2017 eastern domain). A few assets were unable to participate due to a short lead-time to deployment decisions (18 h).

3 April 2017 – VSE Spring 2017 Experiment IOP3A

Event summary: A decaying MCS surged across north Alabama well ahead of what had been anticipated. Upon departure of this MCS and attendant wake low, environmental recovery was slow. A few showers were observed later in the afternoon, and a few of these showers exhibited very weak rotation. Further south, a significant QLCS tornado outbreak occurred across central and southern Georgia.

Deployment summary: Full Spring 2017 western domain deployment, with most assets concentrated in N-central Alabama. UNC-Asheville and University of Georgia personnel surveyed damage associated with an EF1 tornado near Jeffersonville, Georgia.

5 April 2017 – VSE Spring 2017 Experiment IOP3B

Event summary: A significant tornado event was anticipated across the eastern half of Alabama, with a 15% hatched tornado risk outlook issued by SPC. The forecast anticipated robust classic supercell development along a Pacific front/pseudo-dryline structure poised to mix into Alabama during the early-mid afternoon hours, with an environment supportive of very large hail and long-tracked, strong-violent tornadoes. Morning convection over E-central and SE Alabama cleared the region by midday, and atmospheric recovery began in the early afternoon. However, CAPE values observed were only about half of what most models had forecasted (~1000 J/kg instead of 2000 J/kg in most model guidance). In addition, a combination of extremely strong deep-layer shear (0-6 km BWD of 80-85 kt) and very dry air in the mid-troposphere was in place across north Alabama. Low-level SRH was also less than forecast, with hodographs assuming a straight-line character after a small-magnitude turn below 1 km. The combination of nearly straight-line low-level hodographs and entrainment of mid-level dry air aloft reduced the effective buoyancy of parcels and led to skinny updrafts and cells prone to splitting. As the Pacific front reached NE Alabama, more widespread convective initiation was observed along the NW slope of Sand Mountain, along with a weak vortex that formed near the northern tip of Sand Mountain and moved into the Nickajack Lake basin on the Hytop (KHTX) WSR-88D radar. A survey performed by UAH found evidence of EF0 damage associated with this vortex.

Deployment summary: Full Spring 2017 eastern domain deployment.

21 April 2017 – VSE Spring 2017 Experiment IOP3.5A

Event summary: Multicell convection along a stationary front in Middle Tennessee.

Deployment summary: No ground-based operations. P-3 aircraft flew in the vicinity of the Tennessee convection and ran a few clear-air legs across Sand Mountain.

22 April 2017 – VSE Spring 2017 Experiment IOP3.5B

Event summary: WNW flow supercell event across far NE Mississippi, N Alabama, and S Middle Tennessee. Three supercells produced weak tornadoes in north Alabama: an EF1 near Red Bay (Franklin Co.), an EF1 near West Point (Cullman Co.), and an EF0 at Skyline (Jackson Co.). The Jackson Co. supercell underwent transition from a widespread accumulating large hail producing storm in S Middle Tennessee to a tornadic storm in NE Alabama, in close proximity to the KHTX WSR-88D.

Deployment summary: This was not a full deployment of VORTEX-SE ground assets. UAH assets did deploy to the Sand Mountain vicinity, and a P-3 flight took place, with the P-3 flying the Jackson Co. (Skyline) supercell.

26-27 April 2017 – VSE Spring 2017 Experiment IOP4A

Event summary: Weakly organized, sub-severe multicell cluster moved through NW and N-central Alabama around and after midnight.

Deployment summary: Full Spring 2017 western domain deployment.

28 April 2017 – VSE Spring 2017 Experiment IOP4B

Event summary: A few morning HRRR runs suggested the potential for an isolated supercell in NW Alabama in a tornado-supportive environment. A lack of forcing inhibited CI.

Deployment summary: Full VORTEX-SE Spring 2017 western domain deployment. Initial focus on isolated supercell potential was scrubbed in favor of a clear-air PBL deployment mid-afternoon.

30 April 2017 – VSE Spring 2017 Experiment IOP4C

Event summary: A major QLCS tornado outbreak occurred across a large portion of Mississippi during the morning hours. The QLCS slowly weakened as it moved across Alabama during the afternoon, producing isolated wind damage.

Deployment summary: Initial operations split both the western and eastern Spring 2017 domains, with sounding operations focused to the west and mobile profilers focused in the east. After the QLCS passage, all assets moved to the eastern domain in case of new convective development during the evening (which did not materialize).

20 May 2017

Event summary: A QLCS moved through north Alabama during the late afternoon and early evening. The UAH ARMOR radar detected a mesovortex that moved from just south of the radar site at Huntsville International Airport northeastward across the city of Huntsville, ending in eastern Madison County. Areas of damage were noted up to at least EF0 intensity, most notably just west of Redstone Arsenal. A wall cloud was observed by UAH personnel from atop the SWIRLL building, and pictures of an apparent wall cloud were taken from S Memorial Parkway just west of downtown Huntsville.

Deployment summary: No mobile platform operations. Profiling observations from MIPS at SWIRLL and radar observations from ARMOR.

27 May 2017

Event summary: Derecho event from the Missouri Ozarks to northwest Georgia, including numerous instances of wind damage in north Alabama. N Alabama was impacted in the late evening hours.

Deployment summary: Profiler observations and at least one sounding from UAH. UAH personnel surveyed a likely and potentially significant (borderline EF1-EF2 damage) undocumented tornado track in Hamilton, Alabama, associated with a mesovortex sampled by the Columbus, Mississippi, WSR-88D (KGWX).

23 June 2017

Event summary: Remnants of Hurricane Cindy. Mixed-mode QLCS/supercell convection was anticipated, with an accompanying tornado threat. A broken line/QLCS produced several reports of wind damage across NW and N-central Alabama before quickly weakening in NE Alabama.

Deployment summary: UAH mobile assets deployed to the Sand Mountain vicinity in NE Alabama.