Linear Storms

• Supercells also produce severe damaging ______, even when they don’t have ___________
• Many damaging _____ events also form from storms that organize into ______

Damaging Winds!

Squall Lines

• Linear severe thunderstorm development is favored over supercell development when there is strong favorable ______ shear, but not much ____________ shear
• _____ lines of strong-to-severe thunderstorms are called squall lines

Squall Line Example

Squall Lines

• Squall lines sometimes form in advance of _____ fronts or drylines, but not always
• Many are long-lived, lasting ___ or more hours, on average
• Some can persist for more than a ____!
• As their _____ ______ spread out they create new thunderstorm cells to keep the squall line going

Cold Pool--New Cells

Squall Line Animation

Bow Echoes

• Sometimes, a line of storms organizes into a ____ _____
• Bow echoes produce ___________ ______ along the line--especially where the line is "bowing out"
• ____________ ______ are therefore their main threat
• ____________ CAN also occur with bow echoes and squall lines but are usually _______ and infrequent
  

Bow Echo Radar Examples

Iowa Rainfall

• Mult. Choice Question

Iowa Rainfall

• Mult. Choice Answer:
• This is due in part to the ________________ (____)
• Just like the jet stream is the fastest winds near the __________, sometimes around ____ mb we get an area of fast winds (the ____) in the Plains

LLJ

• When conditions are right, a LLJ develops ______ sunset and _______ warm, moist air northward and eastward
• Its formation focuses _________ and _____, often helping storms persist that developed in the afternoon

LLJ

LLJ

• Organized T-storms (like squall lines) often form in the Plains (like SD, NE, KS, etc.) in the afternoon/early evening
• Then the LLJ kicks in later and helps the storms progress farther east, where they could affect Iowa and wake you up in the middle of the night

MCSs/MCCs

• Most of these __________ storm systems are mesoscale convective systems (_____)
• A ______ _____ is an MCS
• Many MCSs have shorter lines of convection, and have an area of lighter rain behind the lines so they look _________
• The _________ MCSs are called _____ (mesoscale convective ___________)

MCC—Fig. 10-13

Tornadoes

• Tornado: a violently rotating column of air extending from cloud to ground
• The column of air does not have to be visible!
• Often you just see a funnel hanging down from the cloud and debris swirling on the ground with nothing in between

Tornadoes

• If the rotation extends from the cloud base but not all the way to the ground, it is called a _______ ______

Tornadoes

• Pressures are ____ in the center of the tornado, so air flows _________ and _____ the tornado, not _____ _____ the center
• Many tornadoes (especially larger ones), called multiple vortex tornadoes, have smaller "__________ ___________" rotating around the main vortex

Suction Vorticies—Fig. 10-19

Tornado Alley—Fig. 10-22

Tornado Alley—See Fig. 10-22

• Tornado Alley is in the Great Plains because it is often the battleground between contrasting air masses we’ve discussed before
• The Rockies and Gulf of Mexico provide a unique environment conducive to tornado production here more than anywhere else in the world

Tornadoes—See Fig. 10-22

• Tornadoes occur during every month of the year, but April through June is the period of greatest tornado frequency

Tornadoes

• In winter and early spring, tornadoes are more frequent in the ______ and __________
• In spring, it's the ___________ _______
• In late spring to summer, it's the __________ _______ and ______ ______

• The 1 am and 5 am images showed the bow shape to the convection—the signature of a bow echo
• Bow echoes produce damaging winds along the line—especially where the line is "bowing out"
• Tornadoes CAN also occur with bow echoes and squall lines