Section 8.3 Tornados
NOAA Jetstream: https://www.weather.gov/jetstream/tornado
Most tornados form underneath supercell thunderstorms (most supercells do not form tornadoes, but most tornadoes form from supercells)
The cloud base underneath the updraft on the rear side of the thunderstorm may lower, forming a rotating wall cloud
A rapidly rotating column of air much smaller than the mesocyclone may protrude beneath the wall cloud
200-250 mbar pressure drop
As water vapor condenses in the air rushing up into this column, a funnel cloud may form and reach the ground, becoming a tornado air rushes up into low pressure core of mesocylone expansion, cooling, and cloud formation descending air in core (may reach ground)
formation & organization
descending air in rear-flank downdraft wraps around mesocyclone
rain/hail in RFD can produce hook echo
becomes focused on surface area of lower pressure
formation of funnel cloud and debris: funnel is rapid condensation of water due to adiabatic cooling
maturity
rapid inflow of warm, moist air into vortex
peak strength and size (usually 100-200 meters in size; but up to ~1 mile in diameter)
RFD begins wrapping around vortex
dissipation
RFD complete wraps around tornado
intensity decreases, tornado tilts with height
drawn into thin, rope-like structure
Radar Signatures
hook echo
TDS (tornado debris signature)
Doppler rotation —> vortex signature
these advances are creating increasing lead times for advanced warning
Tornado Strength
Wind estimation based on observations of tornado damage
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Enhanced Fujita (EF) scale ranges from 0 to 5, with 5 the most damage
The scale uses 28 damage indicators, like schools, barns, and vegetation; the damage to each helps place the tornado on the scale
higher EF number, the more severe the tornado’s wind and damage
Some of the most severe tornadoes are multiple vortex tornadoes