While the heat persists in the southeast, there is a slight threat for severe weather on 4 July 2018. The slight severe weather threat contains central and northeast Nebraska, northwestern Iowa, southern and eastern Minnesota, the southeast corner of South Dakota and northwestern Wisconsin. Main threats for this event include damaging winds, and large hail; however, a tornado cannot be ruled out. There is a mesoscale convective system that has a history of producing hurricane-force wind gusts. The area has been under a severe thunderstorm watch for the overnight hours but as the system moved east, the watch was discontinued. As it moves eastward, the system moves into a less favorable environment. For the remainder of the day, widely scattered thunderstorms are expected to develop into the afternoon. There is risk for general thunderstorms for the central, southeast and east coast of the United States which means storms are not expected to be severe (although it cannot be ruled out).
These storms could put a damper on Independence Day celebrations especially during the evening hours. People who gather outdoors to watch fireworks and parades need to stay weather alert. In the event a thunderstorm threatens your area, seek shelter immediately. Remember, “when thunder roars, go indoors.”
You can read the entire synopsis from the NOAA Storm Prediction Center below:
A long-lived MCS that produced hurricane-force measured gusts around MBG overnight continues to weaken gradually as it moves into somewhat less-favorable environment across northern MN. Still, a severe gust or two remains possible with near-leading-edge convection forced by the cold pool. Widely scattered to scattered thunderstorms, in discontinuous nodes or clusters, are expected to develop through this afternoon near the front and prefrontal/outflow boundaries, from the Upper MS Valley to central/southwestern NE and northeastern CO. Damaging gusts and sporadic large hail are expected from the most intense activity. In addition to afternoon development, this scenario may include regeneration of thunderstorms later this morning over portions of MN along the outflow boundary from ongoing activity, as it impinges on a destabilizing boundary layer. Regardless, rich low-level moisture from central NE northeastward will combine with diabatic surface heating and steep midlevel lapse rates to boost pre-convective/warm-sector MLCAPE into the 3500-4500 J/kg range. Although large-scale ascent aloft should become more displaced from the region through the day, given the track of the aforementioned shortwave trough, that heating along with lift along the boundaries will support pockets of convective development and fairly rapid intensification in that large-buoyancy setting. Initial multicell and messy supercell modes are possible, with upscale clustering anticipated late afternoon into evening. Given the geometry of the mid/upper-level pattern and related northern-stream height gradient, flow aloft and deep shear should decrease with southward extent. Veering wind profiles with height are expected to aid in convective organization, even over southern parts of the outlook area where absolute flow in midlevels will be modest in closer proximity to the axis of the anticyclone. Additionally, an MCV -- now evident in radar composites over northeastern NE -- also may augment deep-layer lift on the mesobeta scale over part of the upper MS Valley region this afternoon.
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ⓒ 2018 Meteorologist Brandie Cantrell
DISCUSSION: Throughout the Spring and Summer-time months, many people around the world who live across many inland areas are often increasingly more concerned about the relatively consistent threat which is imposed by strong to severe thunderstorm activity. As always, when it comes to strong to severe thunderstorm threats, there are many corresponding sub-threats that come along with the storms themselves. First and foremost, you generally will tend to have stronger winds courtesy of powerful downdrafts within more intense storms and then you will also find particularly heavier rainfall as well. However, in addition to both of those severe storm components, you can also sometimes run across hail (and some destructive hail) depending on the specific situation.
Although many people around the world have experienced a hail event of some kind at some point during their lifetime, many people are uncertain or misled for how and why hail stones form in severe storms in the first place. There is a somewhat common misconception that chunks of ice “simply cannot ever occur during the Summer since the ice would melt before reaching the surface of the Earth.” However, this is a sincere error in judgement, since that cannot be farther from the truth. In fact, hail forms within severe thunderstorms via very strong updrafts within a given thunderstorm suspending ice molecules within the higher parts of the thunderstorm. During this process, a decent percentage of said ice molecules will collide and begin to “stick” to one another which increases the overall size of these individual ice molecules into smaller “pea-sized” ice chunks. Depending on the strength of the main updraft within a given thunderstorm, the relatively small ice chunks may simply fall out of the cloud, but if the updraft remains strong enough, they will continue to remain suspended within the thunderstorm.
As they remain suspended, the smaller ice chunks will continue to undergo the process of aggregation and accretion which collectively act to further increase the average size of the smaller “ice chunks” into what atmospheric scientists more commonly refer to as hail stones. Hail stones can be as small as “pea-sized” ice chunks as noted above or as large as softball and/or grapefruit-sized hail stones. Thus, the destructive potential for larger hail stones is tremendous to say the very least. Hence, the next time you or someone you know is projected to be in the path of a nasty thunderstorm with a history of producing large hail, be sure to make the person aware of the incoming and potentially life-threatening situation so they can take proper shelter.
To learn more about other severe weather topics and events occurring around the world, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: When it comes to forecasting and predicting severe weather events, there is no doubt that one of the critical factors in anticipating when and how fast updrafts within a given thunderstorm cell will develop and grow the course of a certain period. A thunderstorm’s updraft is best defined as the core rising column (or metaphorical tube) of air which transports much warmer (and typically ground-based air parcels) higher up into a developing thunderstorm cell. This is shown in the idealized graphic attached above courtesy of Australia's Bureau of Meteorology. Whether an updraft grows quickly or if an updraft happens to develop more slowly will often determine the sort of threats which a given updraft can bring to a given town or city which it is developing over. One thing to understand is that the atmosphere is uniquely a dynamically changing gaseous fluid which means that by its very nature it is nearly always changing on a minute-to-minute and even a second-to-second basis.
For this reason, it is also imperative to understand that such real-time changes in a given dynamic and/or thermodynamic set-up over a given region at a certain time can greatly influence how an updraft develop. For example, in situations where a thunderstorm’s updraft develops and grows more rapidly, this can often facilitate the development of a situation wherein an updraft can quickly begin to generate an increasingly larger threat for very heavy rainfall, large/destructive hail, and damaging wind potential. Thus, if a severe storm is developing with rather vigorous updraft speeds being measured along the way, this would be a situation to concern yourself with if you happen to be in the given storm’s projected path.
On the flip-side, if you are in the path of a given thunderstorm cell which is having a tougher time getting its act together, then there is often much less to worry about. This is because when a thunderstorm’s updraft is having a challenging time growing and intensifying, this consequently greatly lessens the storm’s potential to acquire any in-storm characteristics which are remotely close to those noted above for more severe thunderstorm activity. Hence, when evaluating the given threat level for a given thunderstorm event, one must ask oneself if there is a strong updraft developing within a given storm which can almost always be found out from your local weather broadcaster online, on your local television news station, or on the radio in a given severe weather situation as they are covering it. So, always be prepared and always be paying attention when severe weather threats bear down on your hometown.
To learn more about other severe weather stories and topics from around the world, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz