 There is an enhanced risk for severe weather coupled with a tornado watch for the Oklahoma, Texas, Arkansas and Louisiana, Tennessee, Kentucky, and Mississippi. The tornado watch is for Arkansas, eastern Texas, northwestern Louisiana, and the southeastern corner of Oklahoma. Storms are currently setting up along a surface boundary that extends from northeast Texas into Kentucky. Dewpoints are currently in the mid-upper 60s which is making the atmosphere moist. Potential impacts include isolated strong tornadoes, and damaging winds. The threat is expected to continue over night into Tennessee with damaging winds and an isolated tornado threat. Discrete cells are expected to form which would is favorable for tornado development.
There is also a slight threat for sever thunderstorms for eastern Texas, southeastern Oklahoma, northern Louisiana, northern Mississippi, northeastern Alabama, western Tennessee, western Kentucky, southern Indiana, southern Illinois and southeastern Missouri. The threat remains the same as the enhanced threat with damaging winds and isolated tornadoes. Along with damaging winds and tornadoes, there is also a significant threat for large hail. After the system moves into the Tennessee Valley, the threat will diminish to a marginal and general thunderstorm threat. Stay vigilant and alert throughout the day if you are located within the severe weather threat. Stay up to date on severe weather here! ⓒ 2018 Meteorologist Brandie Cantrell
0 Comments
  Photo Credit: Ryan Hanrahan, NWS Pittsburgh On February 15th, at around 6:40 PM EST, a severe thunderstorm went through the city of Uniontown, Pennsylvania. This storm was severe warned by the National Weather Service in Pittsburgh, PA for being able to produce winds up to 60 mph and “perhaps” a brief tornado. This region of western Pennsylvania has never recorded a tornado during the month of February since records began in 1950.
Once the storms had moved out, there were multiple reports and images from Uniontown surfacing on social media of storm damage. Most people were speculating that the damage had been done by a possible tornado. The first image above shows the radar image and velocity scan of the thunderstorm as it was moving through Uniontown. Velocity scans are a very important tool for meteorologists as it helps depict where the rotation is in a thunderstorm. In response, the NWS office in Pittsburgh sent a survey team down to Uniontown to investigate the damage. The results from the survey were quite historical. The damage in the city was in fact from a tornado that started near the intersection of Phillipi Avenue and Pittsburgh Street. The tornado then traveled approximately two miles before lifting near Kennedy Street in the Woodview Terrace area. On average, most tornadoes are on the ground for less than 10 minutes. This tornado did a good amount of damage in just about 3 minutes. The extent of the damage was equivalent to an EF-1 tornado. This means that the tornado had wind speeds between 86-110 mph. As far as the damage goes, there were numerous power lines down and multiple structures were damaged throughout the city. These structures mainly suffered partial to entire roof damage. Through the path of the storm, many hardwood and pine trees around the area were either snapped or uprooted. The good news however, is that there were no injuries and fatalities from this tornado. The second image above shows a preliminary summary of the damage survey done in Uniontown. Why was this tornado so historical? Although tornadoes do occur every month of the year in the United States, this was a first for the National Weather Service in Pittsburgh. This tornado snapped the record by being the first tornado recorded in the month of February by the Pittsburgh office since 1950. This is also the 11th tornado to form in Fayette county since 1950 with this one being the 3rd EF-1 tornado. And lastly, this makes it the third year in a row that Pennsylvania has recorded a tornado during the month of February. There was the Lancaster and Bradford tornadoes in 2016, the York, Luzerne, and Lackawanna tornadoes in 2017, and now the Uniontown tornado in 2018. To learn more about other interesting and high-impact topics in severe weather from around the world, be sure to click here! © 2018 Meteorologist Joey Marino  Photo Credit: RadarScope
To many of those living where tornadoes are frequent in the United States, the scariest thing is to be caught in a tornado while you are dead asleep at night. Southern states are especially prone to nocturnal tornado events because they tend to have a year-round severe weather season. Although severe weather occurs more frequently during the spring and summer, the mild winters in the south have warmer temperatures and earlier sunset times. These factors increase the risk of nighttime tornadoes in the winter. Even though the probability of these events occurring in the winter is less, when they happen, they are underestimated, and many are unaware of the threat. Nocturnal tornadoes are the most dangerous during the wintertime because of the increased probability of these storms happening at night due to earlier sunset times. The fatality rate is much higher for nocturnal events as compared to daytime events. A study done in 2008 by Walker Ashley and Andrew Krmenec of Northern Illinois University showed that nocturnal tornado events are 2.5 times more deadly than daytime events. This is not only because many are at home asleep and unaware at night, but because many people are at home in residential buildings that are structurally weaker than sturdier commercial buildings. This leaves people more vulnerable if a nocturnal tornado event should occur. Nighttime also makes it hard for storm spotters to spot a tornado and deliver reports to the National Weather Service. So, you’re at home and you want to be aware if a nocturnal tornado happens? There are plenty of actions to take to make sure you and your family are prepared, alerted, and safe when such an event should occur. To be best informed, be sure to follow the suggestions below to keep up to date on weather events, warnings, and emergencies. Before the event:
The day/night of:
Although nocturnal tornadoes are scary, much like a real-life nightmare, they can’t sneak up on you if you are prepared. Having a plan in place and making sure you have a sufficient warning system are keys to being informed. By following the suggestions above, you can wake up in time and take sufficient shelter during these events. The safer you are, the better off you are in case a tornado where to hit your neighborhood at night. Click here to learn more about severe weather! ©2018 Meteorologist Alexandria Maynard   DISCUSSION: Outflow Boundaries, they play an important role in the formation and sustainability of a thunderstorm. But what exactly is this weather phenomenon and how does it form? It all starts with the energy supplier of a thunderstorm known as the updraft. The updraft feeds the storm warm, moist air from the surface to allow it to grow in size and strength. Overtime, precipitation will begin to form inside the thunderstorm as it continues to grow. However, there will be a point at which the weight of the precipitation will become too heavy for the updraft to withstand. This will cause the precipitation and the cold air from higher up in the thunderstorm to fall towards the surface.
This is what is known as the downdraft of the thunderstorm. The cold air associated with the downdraft will hit the surface, spread out, and push the warm, moist air away from the storm. This is called the outflow or also known as the “gust front” and it essentially acts just like a cold front. It brings in cooler air to the surrounding environment as it displaces the warm moist air that was there before. In the radar image below, the light bluish-green line surrounding the thunderstorms is the outflow boundary. There are a few ways that a radar can scan an outflow boundary. The first is due to the change in the density or weight of the air. Scientifically, we know that warm air is less dense than cold air, so the density difference will appear ahead of the storm on radar. The second way is by the objects that an outflow boundary picks up as it moves away from the “parent” storm. An outflow boundary can pick up dust particles and insects which will give a similar image to the radar scan below. Whether the storm continues to thrive or dissipates is all dependent on the speed of the outflow boundary. If the outflow is moving faster than the storm, it will deplete the storm of its energy source and the storm will slowly start to dissipate. However, if the storm can stay near the outflow, the storm will still be able to continue to live until it doesn’t have any more energy supply left. What’s interesting about outflow boundaries is that they can also trigger new thunderstorms around the “parent” thunderstorm. In this case, the parent thunderstorm is the storm that produced the outflow boundary. When an outflow boundary interacts with another boundary, it creates a lifting mechanism and new “baby” thunderstorms can form around the parent. A second way that the outflow can generate new storms is with its ability to act like a cold front. The cold air pushes the warm air up into the atmosphere. The newly displaced warm air acts as a lifting mechanism and prepares the environment for thunderstorm development. Now, that’s just for just a general thunderstorm, but they aren’t the only type of thunderstorm that can produce an outflow. An organized line of thunderstorms or what is known as a Mesoscale Convective System (MCS) also uses the outflow boundary to sustain itself. Using the radar image above, the storms on the left side will continue to strengthen and be severe warned. These storms will continue to have the capability to produce severe weather such as damaging wind gusts and small sized hail. All because the outflow boundary is not that far away from the line of storms as it will continue to supply them with the warm, moist air. While the storms on the right side of the system will eventually become too weak as the updrafts get cut off from its energy supply. These storms will eventually begin to weaken and slowly dissipate as the distance between the line of storms and the outflow boundary is quite large. To learn more about other interesting and high-impact topics in severe weather from around the world, be sure to click here! © 2018 Meteorologist Joey Marino A Look Back at a Historic Long-Duration Convective Event (credit: Weather Forecaster Michael Ames)2/3/2018  DISCUSSION: If you live anywhere other than tornado-prone areas, you’ve probably never heard of the term “derecho”. According to The National Weather Service, a derecho is classified as a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms. These storms are known for traveling along a path of at least 240 miles, and contain wind speeds of 57 MPH (or 50 knots) as well as gusts that can exceed over 100 MPH (or 87 knots).
These violent storms are known for their bow-shaped looking structure, as shown in the image below. This shaped is caused by the strong flow at the rear of the system. This “flow” is movement of air from one area to another. The primary cause of airstream flow is the existence of pressure gradients. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to areas of lower pressure. Thunderstorms flourish on warm, moist air due to the fact that warm, moist is the primary “fuel source” which drives the development and maintenance of convective updrafts. As a result, the majority of derechos occur during the hot, humid days of summer. Image Courtesy of: http://www.spc.noaa.gov/misc/AbtDerechos/images/2012jun29/12jun29_composite.png (**Numbers represent preliminary wind gust reports**) During the mid-summer days of June 29th into June 30th, 2012, a very destructive and long-tracked derecho hit areas of the Ohio Valley and Mid-Atlantic regions of the United States. This particular storm created a swath of damage of over 600 miles long, resulting in a total of 22 deaths, power outages affecting millions and a damage total of $2.9 billion. This particular derecho originally started as a storm in Iowa causing severe hail in many spots. It worked its way eastward towards Indiana with day-time heat indices approaching 100°F helped to fuel this storm. Storms forming to the south in Indiana began to help fuel the parent storm, or in other words the original storm, as surface heating destabilized the region. These two systems intensified as they clashed into each other and worked their way towards Ohio. Wind gusts of over 90 MPH (or 78.2 knots) were reported in Indiana, as well as upwards of 84 MPH (or 73 knots) in Ohio; both of which were recorded near the time at which the event was at its peak magnitude. As the storm approached the Appalachian Mountains, it began to weaken. Once it entered the Washington D.C. metro area, the storm regained momentum and produced wind gusts of 65 - 75 MPH (or 56.4 - 65.1 knots), and slowly started to fall apart as it hit the Chesapeake bay and open waters. The significance of this storm shows that when the conditions are favorable, derechoes can work their way from the mid-western portion of the United States towards the East Coast. While this event wasn’t the first to hit many of these areas, this was one that was a steady reminder that they can happen almost anywhere in the lower 48 states! You can learn more about derechoes as well as this particular event here http://www.spc.noaa.gov/misc/AbtDerechos/casepages/jun292012page.htm! To learn more about other high-impact severe weather events (both past and present), be sure to click here! © 2018 Weather Forecaster Michael Ames |
Archives
May 2019
|
RSS Feed
