Bellwork 5/11 Happy Friday!!  Using the surface map and the data provided, describe why our current weather is occurring. (Today is tricky!!)

Coming Up Today: Finish severe weather, work time Tuesday 5/15: Work day MAKE SURE YOU HAVE DATA FOR THIS DAY! Thursday 5/17: Weather Project due, Begin climate unit

We’ve entered Severe Weather Season in the US! First WI Tornado in Washington County

Severe weather types Thunderstorms Occurrence Features 2,000 in progress at any one time Cumulonimbus clouds Heavy rainfall, hail 100,000 per year in the United States Lightning Most frequent in Florida and eastern Gulf Coast region Live Data

Average number of days per year with thunderstorms

Worldwide Thunderstorm Activity

Thunderstorms All thunderstorms require Warm, moist air Instability (lifting) High surface temperatures Most common in the afternoon and early evening

Thunderstorms—Stages of Development 1. Cumulus stage Require continuous supply of warm air and moisture Updrafts start to form “stocking up” on precipitation depending on the strength of the updraft

Thunderstorms 2. Mature Stage: 3.Dissipating Stage Eventually heavy precipitation falls Gusty winds, lightning, hail 3.Dissipating Stage Warm surface temperatures are gone, ending the updrafts Precipitation becomes light Cooling effect of precipitation triggers the end of thunderstorm activity

Lightning How does it form? Water droplets freeze from the outside in. Water expands as it freezes, causing the icy shell to shatter—lighter ice pieces are pushed upward and heavier water/ice particles fall toward the bottom Friction between these particles causes electrons to be “ripped off” The top of the cloud is then concentrated with positive charges, while the bottom of the cloud is negatively charged. Lightning

How does a lightning bolt form? When the differences in charge have built up enough, the negative charge “looks” for a place to release its charge. Takes the path of least resistance Most lightning occurs within or between clouds. Some occurs between a cloud and the ground

Thunder Heat from lightening causes the air around it to warm rapidly This warm air expands and then quickly cools and contracts This contraction causes the noise we hear after a lightning strike. Speed of sound: ~340m/s Speed of light: 299,792,458 m/s

Severe weather types Tornadoes Local storm of short duration Features Rotating column of air that extends down from a cumulonimbus cloud Low pressures inside causes the air to rush into the center

Tornadoes Occurrence and development Most frequent from April through June Exact mechanism of tornadoes formation is not known Basic observations show us: 1. Strong winds create horizontal rotation 2. Updrafts (associated with thunderstorm) force the rotation in a vertical position 3. Mesocyclone created & MIGHT touch down on the ground

Only about HALF of the mesocyclones formed become tornadoes!

Conditions for the formation of tornadoes Occur most often along a cold front Associated with huge thunderstorms called supercells Cold cP air mixing with warm mT air Larger the difference, larger the storm

How do we track a tornado? Doppler Radar VORTEX2 projects TOTO…(didn’t work)…Twister instrument was modeled after this

Measuring a Tornado Can only be measured AFTER a tornado has passed Intensity measured by the Enhanced Fujita intensity scale Can only be measured AFTER a tornado has passed

Severe weather types Tornadoes Tornado forecasting Difficult to forecast because of their small size Tornado watch To alert the public to the possibility of tornadoes Issued when the conditions are favorable Covers 65,000 square km (25,000 square miles)

Severe weather types Tornado warning is issued when a tornado is sighted or is indicated by weather radar Use of Doppler radar helps increase the accuracy by detecting the air motion

Work time Hurricane Lab Weather project Make sure you have all of your data collected Start organizing/analyzing the data you do have!