The die has been cast and a majestic cumulonimbus cloud is born. The information below will further explain the development of thunderstorms when all of these ingredients are available. Once downdrafts become dominant and a storm "rains itself out" as the cold pool grows larger and cuts off the storm from warm, moist air for its updraft, the storm dies. With the updraft fading and precipitation still sustaining the downdraft (albeit weaker because rainfall rates have also decreased), the downdraft now dominates the single-cell storm, a state which defines the dissipating stage. The splashdown and subsequent spreading out of the downdraft at the ground is akin to water from a kitchen faucet hitting the sink below. Cut off from a supply of buoyant, maritime-Tropical air, the single cell's updraft weakens. Also note that precipitation does not usually fall straight down into the core of the updraft. But, thunderstorms never really erupt randomly, even if it appears that way. What happens when thunderstorms form in environments where vertical wind shear is stronger? A basic thunderstorm (single cell) goes through three phases during its lifetime: cumulus, mature, and dissipating. Individual cells usually last 30 to 60 minutes, while the system as a whole may last for many hours. But, these initial cumulus or cumulus congestus clouds typically don't become thunderstorms. In the first stage (cumulus), we see the cloud that will become the thunderstorm starting to form and grow due to the rising thermal (or updraft). Rain is heaviest. An air-mass thunderstorm, also called an "ordinary", "single cell", or "garden variety" thunderstorm, is a thunderstorm that is generally weak and usually not severe. Please send comments or suggestions on accessibility to the site editor. I should already be familiar with: Fronts, How Clouds Form, Precipitation Types. Have you ever heard a weather forecaster predict "random" afternoon "pop-up" thunderstorms on a summer day? Figure A. In the dissippating stage of a single-cell thunderstorm, the cloud is dominated by downdrafts, and a large area of precipitation and cold outflow are present. When the downdraft hits the ground, it begins to spread out in all directions. We'll explore further beginning in the next section. Lightning is most frequent. They are commonly found in the spring and summer, and can bring brief periods of heavy rain and hail. With that said, let's take a closer look at the development and life of single-cell thunderstorms. The Pennsylvania State University). Downdrafts develop for essentially two reasons: the drag exerted by falling raindrops, and cooling associated with the evaporation of small raindrops (via entrainment). Then how about some holiday weather history! As the name implies, there is only one cell with this type of thunderstorm. Some portions adapted from original course materials by David Babb and Lee M. Grenci. But, the hallmark of the mature stage is the simultaneous presence of an updraft and downdraft within each cell. Effectively, new cumulus forming along the gust front hog all the moisture, hastening the storm's demise. Course Author: Steven Seman (Assistant Teaching Professor, Department of Meteorology and Atmospheric Science, College of Earth and Mineral Sciences, Single-cell storms may produce brief heavy rain and lightning. The College of Earth and Mineral Sciences is committed to making its websites accessible to all users, and welcomes comments or suggestions on access improvements. This can last between 30 minutes to an hour. During this stage, the growing towering cumulus cloud is dominated by updrafts, and updrafts accelerate to roughly 10 meters per second as air from miles around converges to feed the updrafts. Single-cell storms may produce brief heavy rain and lightning. If you see a thunderstorm coming, knowing what stage it is in could help you determine how … 2217 Earth and Engineering Sciences Building, University Park, Pennsylvania 16802 The Pennsylvania State University © 2020. The birth, life, and death of a single-cell storm typically takes less than 45 minutes. Cloud tops are highest. Take, for example, this image of radar reflectivity from 2055Z on June 14, 2015 and note the widely scattered thunderstorm cells across the Southeast U.S. Before a full-fledged thunderstorm can develop, cumulus clouds must grow into cumulus congestus clouds. Radar reflectivity is greatest. The site editor may also be contacted with questions or comments about this Open Educational Resource. All is not lost, however. Essentially, single-cell thunderstorms go through three distinct stages during their lives, but the process gets started when positively buoyant air parcels rise to the point of net condensation, forming cumulus and perhaps cumulus congestus clouds (like the one in the image on the right) typically in the late morning or early afternoon hours. When this happens, a gust front can form. Multicell Cluster Storms A group of cells moving as a single unit, with each cell in a different stage of the thunderstorm life cycle. Although single-cell storms don't often produce damaging wind gusts, they can do so on occasion (particularly vigorous single-cell thunderstorms are referred to as "pulse storms"). They are typically driven by heating on a summer afternoon. The rising updraft of air will begin to cool and condense as it rises, and in the case of thunderstorms, the thermal can travel tens of thousands of feet up before it finally stops! During dissipation, the updraft is very weak or non-existent, and the downdraft is the main dominant force in the thunderstorm. Eventually, clouds graduate from fair-weather cumulus to towering cumulus congestus. Single-cell thunderstorms occasionally may also produce small hail in the mature stage (usually not large enough to cause damage), but all of this vigor is fleeting, with a single-cell's mature stage lasting ten minutes or so. Indeed, the rain-induced downdraft that splashes down and spreads out laterally inevitably cuts off the inflow of warm, humid air into the storm's updraft. Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Let's explore the process, as we investigate the first stage in a single-cell thunderstorm's life cycle -- the cumulus stage. The reason they often appear random is because we don't have the capability of predicting exactly where and when local conditions are just right for storm initiation. Why do I care? In the towering cumulus stage, the rising updraft will suspend growing raindrops until the point where the weight of the water is greater than what can be supported. Rather, precipitation moves a bit horizontally with upper-level winds before falling into air with lower relative humidity (below the cloud base). Figure C. A Gust Front located ahead of an approaching thunderstorm. That’s said, let’s get into the details of how thunderstorms are formed. Depending on thunderstorm type, a storm may go through it only once (single cell), or multiple times (multi-cell). You can think of a downdraft as a blob of cool air in the cloud that is heading toward the earth’s surface (opposite of an updraft). Rather, precipitation moves a bit horizontally with upper-level winds before falling air with lower relative humidity, paving the way for evaporational cooling and downward acceleration. Evaporational cooling increases the density of descending parcels of air, increasing their negative buoyancy and downward acceleration. The thunderstorm slowly dies out and leaves only wispy clouds behind as evidence of its existence. Most thunderstorms undergo three phases in their formation, namely: 1. The John A. Dutton e-Education Institute is the learning design unit of the College of Earth and Mineral Sciences at The Pennsylvania State University. A schematic of the mature stage of a single-cell thunderstorm. This courseware module is part of Penn State's College of Earth and Mineral Sciences' OER Initiative. To recap the stages in the life of a single-cell thunderstorm, I created a short video (3:22) highlighting the key characteristics of each stage and their corresponding presentations on idealized radar imagery. Figure A. Gust fronts associated with single-cell thunderstorms can spark other thunderstorms (warm, moist air converging at the gust front is forced to rise), but, most times they don't. As you've learned, thunderstorms tend to form when air parcels can become positively buoyant after being given a nudge upward (perhaps from low-level convergence along a cold front or sea-breeze front). Single-Cell Thunderstorms: A textbook, run of the mill single storm that develops, grows, and dies like described above would be classified as a single-cell thunderstorm. As a result, the once majestic towers that characterized the mature stage of the storm gradually vanish. If you see a thunderstorm coming, knowing what stage it is in could help you determine how much impact it will have on the area around you. The full life cycle process takes about 30 minutes to complete.