Giant Hail..............

As we continue with severe weather awareness week today I will discuss large hail and the severe storms that have produced some of the largest hail on record. Hail is a type of precipitation which grows inside the thunderstorm due to strong updrafts suspending ice crystals in the storm cloud until they grow to a point where the updraft can no longer support them and they fall to the Earth. The largest know hail stone to strike the United States is in the photo below from a storm in Aurora, NE.



This hailstone is just over 7” in diameter and 18.75” in circumference. It was the largest stone in one piece from this storm however, there were reports of larger stones that broke apart on impact with the ground. In some places up 12” diameter creators were left on the ground. Below is a short movie of the volumetric radar return from the storm that produced this giant hail. What is amazing about this storm is not only the height, topping out over 61,000’, but the strong reflectivity near the top of the storm, 60dbz at nearly 46,000’.



Another powerful storm that produced very large hail was right here in East Texas last year when softball size hail was reported near Bullard on February 5th. Below is a short movie of the volumetric radar return from the storm that produced this giant hail. Notice the storm was nowhere near the height that produced the giant hail in Nebraska. This storm formed during the cool season so you do not need to have storms as high to produce very large hail because the mid levels of the atmosphere are much colder.



You can imagine that chunks of ice the size of softballs or larger can be very dangerous if caught outside. The last known death in the United States occurred in March of 2000 when a man in Lake Worth, TX was hit in the head by softball size hail. Now the Great Plains are known for very large hail at times but parts of south Asia and China are known for devastating hail storms. In July of 2002, 25 people lost their lives during a hail storm in the Henan Province of China. Bangladesh is also notorious for very large hail. In fact the heaviest hailstone on record fell there in April of 1986 and weighed just over 2.2 pounds. I have not seen the actual dimensions on this stone but I would have to imagine it would have been slightly larger than volleyball size.



So how can a storm suspend ice particles this size? It all has to do with the strength of the updraft. Once we start to see hailstones the size of softballs or larger, the storm’s updraft speed will exceed 100mph! This was the case back in October 2007 when a massive hail storm hit Santo Cristo, Brazil. In the photos you see stones over 10cm in diameter, or about the size of softballs.





So unlike with tornadoes, the United States is not the hail capital of the world. While we get our fair share, even here in East Texas, other parts of the world see this severe weather phenomenon as well. Large hail is commonly found along the front range of mountain chains with the storms along the Himalayas producing the most and largest hail on Earth.

Valentine's Night Storm........

For all those lovers of exciting weather Cupid shot his arrow into the atmosphere and whipped up some elevated thunderstorms Valentine’s Night bringing a vivid lightning show and small hail to parts of East Texas. The lightning shots you see here were taken from my front porch as a strong storm moved out of Eastern Henderson County into Smith County.




This storm produced a large amount of small hail, covering the ground and causing hazardous travel along 346 from Flint to Whitehouse. The largest hailstone I found was penny size which technically is severe near the intersection of 346 and Oakbrook. These storms fired with a combination of many atmospheric conditions which came together over East Texas.



First, in the mid levels of the atmosphere a weak disturbance was entering West Texas causing the winds to diverge over East Texas. This causes the air to rise which could lead to clouds and precipitation. Second, a strong jet stream in the upper level of the atmosphere was moving just to our south. This put East Texas in what we call the left exit region of the jet stream which also adds in lifting the air.


Third, strong wind shear was noted in the atmosphere from 6,000’ to 30,000’. This will help aid in thunderstorm development by pushing the rain cooled air downstream, away from the storms updraft allowing the storm to become stronger.





The only thing missing for thunderstorm development, moisture. The low levels of the atmosphere where we normally find the moisture needed for thunderstorm development were too dry for surface based storm development. However, in the lower mid levels of the atmosphere a thin layer of moisture was moving into East Texas. This was all that was needed to help fire what we call elevated thunderstorms. Since the low levels of the atmosphere were dry, we were giving a vivid lightning storm with great visibility, giving many photo opportunities.

Tuesday Night's Severe Storms!

A line of severe Thunderstorms raced across East Texas Tuesday night into Wednesday morning bringing strong winds, hail, and even an EF-1 tornado which touched down in Northwestern Smith County and traveled along the ground for 6.8 miles into Southern Wood County. This tornado was formed form a phenomenon we call a “bookend vortex.” If you look at the short radar loop(shown below) of the storms as they moved through parts of East Texas, you will notice they take on the shape of a bow, or “bow echo.” This is because near the center of the line of storms very strong winds are punching in causing the line to race forward in the center forming the bow shape. It is here where you usually find the strongest wind in some cases over 80mph. This is what caused the damage in the Sunrise Shores area of Henderson County. These strong winds continued to race east affecting parts of Smith County causing widespread power outages and tree damage.


In a highly sheared environment, which we had Tuesday night, sometimes on the ends of a “bow echo” will form an area of rotation called a “bookend vortices.” It is called this because the rotation is located at the ends of the bow shape. In a highly sheared environment winds will cause this rotation to strengthen. The environment on the northern counter-clockwise circulation in a highly sheared atmosphere can become favorable for tornado development.




As the northern end of the bow echo entered Northern Smith County we can see a rear inflow notch or an area where winds are punching into the back of the storm. This is depicted in the radar image above with the air flow noted by arrows. The north and south ends of strong bow echoes will have these bookend vortices continuing to push are towards the center of the line helping create the widespread wind damage. The northern vortex began to tighten and eventually lead to the development of the tornado.




In the next radar image taken five minutes later, you can start to see precipitation wrapping around the vortex similarly to what you would find in a mesocyclone found on the southwest side of a classic supercell.(Mesocyclone is a localized area of low pressure formed by the most severe thunderstorms called supercells. Mesocyclones are what give birth to the strong violent tornadoes like the one the struck Lone Grove, OK Tuesday.)



Finally in the last image when can see the air rotation has tighten and eventually was stretched in the storms updraft causing the tornado to form near the intersection of CR 482 and CR 483 in Northwestern Smith County. At the time of the image it appears the storm has already moved past however, we must remember that in a highly sheared environment the precipitation is being pushed forward, away from the storm. Over this region of East Texas the radar beam which sends back and image is nearly 10,000’ in the atmosphere so the actual updraft of the storm lags behind the echo show by 5000’ or so.



So how do we know it was a tornado? Well, the next photo paints the picture pretty clear. In the photo I have four points marked A, B, C, and D. “A” is a pine tree which was snapped in half. “B” is the top of the snapped tree which was blown to the east. “C” is another pine tree next to “A” which was blown down to the northwest. And finally “D” is another tree in the background blown down to the northeast. It is this scattering of debris which shows us it was a tornado. If we were looking at straight line wind damage, all the trees would be facing the same direction like we showed from “Chopper 7” in the Sunrise Shores area of Henderson County. Now just because the damage in Sunrise Shores was not caused by a tornado does not mean it was not as bad. In some cases it looked much worse than the tornado damage. We all seem to get caught up in the fact that anytime damage occurs from wind, a tornado must have hit us. 90 mph winds will do a tremendous amount of damage whether it is straight or blowing in a circle. This is why all severe thunderstorms should be taken very seriously.



Here are a few more photos I shot of the damage. The first photo shows tree debris down and scattered about. My daughter Halen is making sure Daddy gets all the information.





The next photo is metal roofing or siding carried at least a ½ mile. There were no close structures this could have come from.




So what have we learned from this event. Bookend vortex tornadoes can and do form with very little or sometimes no warning at all. But you can be assured that the StormTracker Weather Team watches all “bow echoes” very closely and will break in to warn the public if we think a tornado is forming. You may remember us breaking into programming last year when a bookend vortex produced an EF-1 tornado took a 21 mile path through Gregg and Rusk counties. These events are something we have to live with in this part of the country and we will always be watching the skies to keep you safe.

One Year Ago Today!

One year ago today we were watching a serious severe weather episode unfold that would later be known as the “Super Tuesday Outbreak” By early Tuesday Afternoon the Storm Prediction Center placed most of the Mid South Region under a “High Risk” of severe thunderstorms and tornadoes with a moderate risk of severe storms as far west as East Texas. By the end of the day 131 reports of tornadoes and 126 reports of large hail pelted the country.



The atmosphere was increasingly becoming unstable throughout the early afternoon in East Texas as plenty of sunshine helped boost temperatures into the low 80s, almost unheard of for early February. By 4:00PM in the afternoon, a line of scattered supercells exploded along a fast moving cold front through East Texas. Three of these storms would end up producing a significant amount of damage across East Texas through the late afternoon.



By 4:30PM the city of Lindale was being pelted with golfball size hail causing widespread damage to cars and homes. Lindale ISD canceled classes through the end of the week to repair damage to Velma Penny Elementary School and E.J. Moss Intermediate School. This storm later moved north into Upshur County causing strong winds and quarter size hail.



At the same time the second supercell was about to unleash some of the largest hail seen in East Texas. The town of Bullard was crushed by hail up to the size of softballs. This hail damaged numerous cars; yours truly had his car totaled during this storm. While surveying the storm damage with the national weather service, we found houses along Lilly Lane in Bullard where holes were punched through the siding of the home.



Below are a couple a three dimensional views of this storm. Notice on the first image you can see a white core in the center of the cell. The next image it is gone. The first image is showing extremely large hail being held up by the storms updraft. Between the first and second image, the hail became too heavy to hold by the storm's updraft so it fell on the town of Bullard. In order for a storm to hold hail this large above the surface the updraft speed, or wind rising through the storm, to be over 100 mph.





The storm continued to move northeast producing large hail through parts of Smith County. Below is an image of 2.75” hail, or baseball size from my yard about 3 miles northeast of the softball size hail report. Of course I did not get these stones until about 30 minutes after the storm so, they were probably closer to 3 to 3.25” in diameter.



All three of these storms showed strong rotation in the mid levels of the atmosphere and we were under a tornado watch however, with these storms forming along a cold front, the warm surface air you need to produce a tornado was undercut by the rapidly moving cold air underneath these storms. However, as supercell #2 moved through Southeast Smith County, for a brief period of time the circulation of the storm was able to outrun the cold air from the front and produce an EF-1 tornado near Arp along Hwy. 64 East of Tyler. This tornado was on the ground for only about 30 seconds but in that time tore a mile long path of damage snapping trees and damaging a large barn, just missing a home. This is an interesting case of how a tornado can develop, touchdown, and then dissipate in less time than it takes our Doppler radar to make a complete scan. Another good reason to take all severe thunderstorms seriously.



The third supercell developed and moved through Cherokee County producing golfball size hail just east of Jacksonville. This cell also showed strong midlevel rotation however it too was undercut by cold air at the surface.



This storm system later developed into a massive tornado outbreak across the Mid South and Southeast. 2 EF-4 tornadoes touched town in Northern Alabama and dozens of people lost their lives across the Southeast. These storms formed from a combination of a cold winter storm interacting with very warm Gulf air which spread across the southeastern part of the country. With the cold midlevel temperatures combined with the record warmth at the surface, the air mass became very unstable allowing thunderstorms to explode.

Snow??????

Some places across East Texas awoke to what appeared to be snow yesterday. But if you were awake during the event, and most people were, you would know that a hail storm effected parts of the area Sunday night. I line of thunderstorms erupted ahead of a fast moving cold front Sunday night producing gusty winds and lots of small hail. We did receive reports of up to golf ball size hail in Montalba but most of the storms produced pea size hail. A storm that formed along the Rusk Panola county line produced a heavy dose of pea size hail which lasted for about 20 minutes. This caused an accumulation of small hail in some areas to reach 10” in depth. Now this occurs occasionally in western states but an accumulating hail even is very rare for East Texas. A big thank you to Rusty Nix for sending me photos of the hail accumulation.