11.1: Ingredients for Thunderstorms
- Page ID
- 44874
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Thunderstorm Formation
Thunderstorms form when there is a sufficient amount of heat and moisture in the air. Heat allows the warm, moist air near the surface to rise in an upward motion, forming an updraft. The moisture in the air begins to cool and condense, forming clouds. Latent heat is released during this process, allowing for the continued upward movement of air. As this air continues to rise, the process creates strong upward and downward winds, leading to a mature cloud stage characterized by heavy precipitation, lightning, and thunder. Such clouds are full of liquid droplets, ice, hail, and graupel, which can be detected clearly by weather radars. Figure \(\PageIndex{1}\) is a weather map of surface weather conditions, fronts, and precipitation across the United States at 2100 UTC (4 pm Central Daylight Time) on May 28, 2019.
- According to Figure \(\PageIndex{1}\), Kansas City, in western Missouri, was reporting a temperature of 74°F and a dew point of 71°F. Except for locations along the US Gulf Coast, Kansas City’s dew point was _____ than most of the locations in the Continental United States.
- higher
- within a degree or two
- lower
Remember, the dew point is the temperature to which air must be cooled at constant pressure for it to become saturated. It is a good indicator of the amount of moisture in the air. When the air's temperature drops to its dew point, the air becomes saturated (100% relative humidity).
- Kansas City's Dew Point temperature was only a few degrees different from its air temperature. This indicates that the air was _______.
- close to saturation
- very dry
Areas of heavy rainfall and thunderstorms are indicated on weather maps such as Figure \(\PageIndex{1}\) as a series of orange/red shadings embedded in larger areas of precipitation. Irregularly shaped blue/green/yellow blobs indicate different intensities of reflected radar echoes.
- The presence/lack of such shading indicate that there ________ thunderstorms near Kansas City at 2100 UTC.
- were
- were not
- On the other hand, consider San Francisco, California, which at 2100 UTC has an air temperature of 64°F, and a dew point of:
- 66°F
- 57°F
- 51°F
- 48°F
- Therefore, San Francisco's air is _________ than Kansas City's.
- more humid
- drier
- The appearance/lack of orange/red shadings embedded in radar echoes near San Francisco indicate that thunderstorms _________ occurring in the area.
- were
- were not
While heat and moisture are key ingredients for Thunderstorm formation, other dynamics in the atmosphere can also aid in the formation of thunderstorms. For example, consider Des Moines, in Central Iowa, with an air temperature of 57°F and a dew point of 54°F.
- Des Moines is ________ than Kansas City.
- much warmer/wetter
- much cooler/wetter
- much warmer/drier
- much cooler/drier
- However, there _______ thunderstorms near Des Moines.
- are
- are not
This suggests that some other dynamics are in play. Other elements that can allow thunderstorms to form include frontal lifting: a meteorological process where warm air is forced to rise over a colder air mass at a weather front, upper-level divergence: the spreading out of air in the upper levels of the atmosphere, and vertical wind shear: a change in wind direction/speed with height. The presence of Convective Available Potential Energy (CAPE) can also greatly influence thunderstorm formation.