Section 8.1 Thunderstorm development
NOAA Jetstream: https://www.weather.gov/jetstream/ingredient
a mechanism is necessary for lifting; this can often take place along a cold front, especially if advancing into warm, moist (mT) air
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thunderstorm development is tied closely to the stability of the atmosphere
stability index: take a parcel and lift it adiabatically (DALR) to saturation, then lift saturated parcel (SALR) to 500-mbar level
compare parcel temperature to environmental temperature
Lifted Index = T(env) - T(parcel)
Lifted Index values below zero are unstable (the parcel is warmer than the environment): that is, the parcel will be buoyant relative to its surroundings
Development of single-cell (local) thunderstorm (or “air-mass” thunderstorm)
NOAA Jetstream: https://www.weather.gov/jetstream/life
occurs by thermal convection, orographic lifting, or surface convergence
developing stage - mature stage - dissipating stage
development stage
lifting to LCL and cumulus-type cloud formation that expands vertically and horizontally
entrainment of surrounding dry air; evaporation cools the air within the cloud
moist air flowing upward begins producing an updraft
droplet formation by collision and coalescence
mature stage
precipitation begins to fall from the cloud
rain, lightning, possibly small hail
rain helps produce a cool downdraft
dissipating stage
main factor: updraft weakens and collapses (downdraft begins to dominate and cuts of upward supply of moisture)
moisture content decreases and supply of latent heat diminished
precipitation weakens and cell dissipates