severe weather (weather and climate)

Thunderstorm

Process by which unstable parcels rapidly rise, condense, and produce precipitation and lightning.

Ingredients for thunderstorms

Lift, instability, and moisture

In a thunderstorm:

Warm air in low-levels, moist in low-levels, and cool in uper-levels

Ingredients for a severe thunderstorm;

Shear, lift, instability, moisture

Shear

Change of wind a\speed or direction with height

Severe thunderstorms:

Winds gusting more than 58mph (50 knots), hail above 1 inch in diameter, and tornados.

Thunderstorms may develop:

Within an airmass, along a front, or along mountain slopes

Thunderstorms are characterized by:

The buildup of cumulonimbus clouds and can be associated with heavy rain, sleet, and hail, strong winds, and tornadoes.

Air mass thunderstorms

isolated, short-lived thunderstorms that are fueled by the rapid, upward movement or warm, moist air. Rarely become severe

Air mass thunderstorms typically pass through 3 stages:

Cumulus stage (developing), mature stage, and dissipating stage.

Cumulus stage

Dominated by updraft and little to no precipitation

Mature stage

significant precipitation forms and reaches the ground. Cold air descends to the ground (downdraft).

Dissipating stage

Dominated by downdraft, precipitation suppresses updraft. Cold air at the surface cuts-off the thunderstorm from the warm moist air. Dying stage of storm.

Squall line

Narrow band of thunderstorms. Can form along fronts and as disorganized thunderstorms and turn into an organized line of thunderstorms.

Squall lines can produce:

Severe weather

Downbursts

Strong, downdrafts that caused exceptionally strong winds, pose a risk to aircraft, and are difficult to predict or detect.

Macrobursts

Damage expanding more than 2.5 miles

Microbursts

Damage expanding less an 2.5 miles

Supercell thunderstorms

Highly organized, generally isolated thunderstorm that is characterized by a storm-scale vortex called a mesocyclone

Derecho

powerful, wide-spread, long-lived types of squall line. Wind damage extends more than 240 miles and include wind gusts of 58 mph or greater.

Lightning

Flash of light that results from the discharge or electricity between positive and negative charges

Cause of lightning

Charge separation within the cloud and negative cloud base induces a positive charge on the ground

Thunder

the sound wave produced by the expansion of air heated rapidly

Far from lightning:

Prolonged sound, not loud, rumble

Close to lightning:

Short report of sound, loud, “crack”

Funnel cloud

A violently rotating column of air but it does not extend to the ground

Tornado

A violently rotating column or air that extends from a cloud to the ground

Tornadoes form with:

The formation of a rear flank downdraft

Tornadoes are rated:

After a damage assessment has been made by the NEWS using the enhanced fujita scale

Tropical cyclone

A rotating low pressure system that originates over warm, tropical or sub-tropical waters

Tropical cyclones are categorized by:

Wind speed using the Saffir Simpson Scale