Severe Weather Test 3

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Cold Wave Impacts 1

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Large geographic areas are often affected by cold waves relative to other severe winter weather.

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Cold wave Impacts 2

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Average about 30 deaths per year.

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Cold wave Impacts 3

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Economic losses from agriculture, water pipes and commercial slowdowns.

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Cold Wave Impacts 4

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Impacts depend somewhat on geographic location. Southern states are most impacted.

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Anticyclones 1

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A weather system characterized by relatively high surface pressure compared with the surrounding air: surface winds blow clockwise in Northern Hemisphere (counter-clockwise in Southern Hemisphere) and outward.

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Anticyclones 2

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-- The Core of cold wave at the surface.

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Anticyclones 3

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The surface high-pressure centers form by the cooling of air in the lower troposphere.

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Formation of cold air mass 1

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Originates on plains of west-central Canada in winter.

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Formation of cold mass 2

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Long winter nights.

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Formation of cold air mass 3

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Snow covered - radiates infrared energy, reflects sunlight.

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Formation of cold air mass 4

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Cold skies = rotational cooling.

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Formation of cold air mass 5

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Light wind = favoring air mass formation

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Cold Wave weather Pattern 1

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Cold air is very shallow, extending 1-2 kilometers above ground.

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Cold Wave weather Pattern 2

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A strong Pacific low enhances the jet stream.

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Cold Wave weather Pattern 3

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High pressure systems usually have clear skies and light winds! They "trap" the cold air!

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Mountain storms

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Air must rise nearly 2 kilometers = majority of moisture condensed out as Pressure.

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Source of mountain snowstorms 1

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Develop during the passage of large scale weather systems.

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Source of mountain snowstorms 2

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Many of those systems originate over the central and western Pacific Ocean.

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Source of mountain snowstorms 3

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Temperature of the surface air over the ocean is 40 to 60 degrees F.

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Source of mountain snowstorms 4

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Laden with moisture.

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Source of mountain snowstorms 5

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Moisture streams are called atmospheric rivers.

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Source of mountain snowstorms 6

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Typical weather systems and the atmospheric river.

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Source of mountain snowstorms 7

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Strong cyclones develop over the Pacific, mainly south and east of the Aleutian Islands --- one of the preferred regions for extratropical cyclone formation (Aleutian low)

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Source of mountain snowstorms 8

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Life cycle of these cyclones occur mostly over open water.

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Source of mountain snowstorms 9

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Occluded when arrive at west coast.

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Source of mountain snowstorms 10

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T-storms are rare and air is relatively stable.

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Storms on the East slope of the Rockies 1

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Storms can occur with relatively, moist eastern wind.

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Storms on the East slope of the Rockies 2

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Less common, but can produce enormous amounts of snow (more than 1 foot)

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Storms on the East slope of the Rockies 3

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Two pressure patterns: High on the north, and low on the south (Four Corners low).

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Storms of the East slope of the Rockies 4

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Upslope storm.

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Thunderstorm 1

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A thunderstorms is one of several comulonimbus clouds accompanied by lightening and thunder.

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Thurderstorm 2

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Four elements of formation: Moist air, unstable air, lifting force and vertical wind shear.

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Thunderstorms Hazards

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Lightning, hail, tornadoes, flash floods.

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Components of a Thunderstoms

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Lightning, precipitation, hail, wind, tornadoes.

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Types of Thunderstorms: Airmass or Ordinary Cell 1

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Limited wind shear.

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Types of Thunderstorms: Airmass or Ordinary Cell 2

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Often form along the shallow boundaries of converging surface winds.

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Types of Thunderstorms: Supercell or Severe 1

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Precipitation doesn't fall into the updraft.

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Types of Thunderstorms: Supercell or Severe 2

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Cluster of cells at various developmental stages due to cold outflow undercutting updraft.

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Thunderstorm stages 1

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Developing (cumulus)

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Thunderstorm stages 2

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Mature, notice the heavy rain.

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Thunderstorm stages 3

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Dissipating

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Thunderstorms: Single Cell

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Heavy rain (brief), small hail, wind gusts/downbursts, and weak tornadoes.

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Thunderstorms: Multicell 1

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Flash floods, moderate hail, wind gusts/downbursts, weak tornadoes.

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Mesoscale Convective Complex 1

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An organanized mass, or collection, of thunderstorms, that extends across a large region called a mesoscale comvertive complex (MCC).

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Mesoscale Convective Complex 2

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With weak upper level winds, such MCC's can regenerate new storms and last for upwards of 12 hours and may bring hail, tornadoes and flash floods.

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Mesoscale Convective Complex 3

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They often form beneath a ridge of high pressure.

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A squall line (MCS)

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Thunderstorms: Multicell 2

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Clusters

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Thuderstorms: Multicell 3

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Lines: Squall lines and Bow echos.

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Supercell Thuderstorms 1

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Defined by mid-level rotation (mesocyclone), highest velocity near updraft core.

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Supercell Thunderstorms 2

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Supercell form under the following conditions: High CAPE, capping layer, cold air aloft, large wind shear.

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Supercell Thunderstorms 3

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A classic tornadic supercell thunderstorms showing updrafts and downdrafts.

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Supercell Thunderstorms 4

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Thunderstorms; Supercell

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Heavy rain (flash flood), large hail, strong wind gusts/downbursts, and strong tornadoes.

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Tornado life cycle

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4 stages

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Tornado formation 1

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Step 1: Tilting wind shear cause the storm's updraft to totate.

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Tornado formation 2 s

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Step 2: The formation of a low-level mesocyclone

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Tornado formation 3

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Step 3: Rotation extends to the ground, top-down process, bottom-up process, and Tornadoes formation in a non-supercell storm.

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Tornado formation 4

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Tornadoes likely occurs on the south side of the mesocyclone (the hook echo)

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Classic Supercells 1

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Preferred Spotter Position is Dependent on Storm on Storm Motion: take a position in the inflow to the right of the storm track.

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Classic Supercell 2

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Benefits of This Vantage Point: Sense Inflow/outflow, unobstructed view of Updraft region, and Safety.

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Seasonal March of Tornadoes

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Hail Storm Dynamics

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Hail Stone Growth 1

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Wet growth: the water does not freeze on the ice immediately. Instead, liquid water spreads across tumbling hailstones and slowly freezes. Since the process is slow, air bubbles can escape resulting in a layer of clear ice.

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Hail Stone Growth 2

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Dry growth: the water droplet freezes immediately as it collides with the ice particle. The air bubbles are "frozen" in place, leaving cloudy ice.

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Hail Days 1

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Mean annual number of days with hail > 0.75 inches

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Hail Days 2

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Mean annual number of days with hail > 2 inches.

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Hailswath and hail-streaks 1

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Hail tornadoes are similar in term of the intermittency of their paths.

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Hailswath and hail-steaks 2

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Hailswaths: continious areas with wider and longer area of hailfall (areas inside dash lines).

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Hailswath and hail-streaks 3

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Hail streaks: small continuous region of hail coverage. Usually 1 - 2 wide and very in length from a few to > 60 km.

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Classification of Tropical Weather Systems 1

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Organized thunderstorm cluster, no closed circulation: Tropical Disturbance.

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Classification of Tropical Weather Systems 2

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Identifiable pressure drop and closed circulation: Winds less than 39 miles per hour; Tropical depression.

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Classification of Tropical Weather Systems 3

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Identifiable pressure drop and closed circulation:39 miles per hour wind less than 74 miles per hour; Tropical storm.

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Classification of Tropical Weather Systems 4

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Identifiable pressure drop and closed circulation:74 miles per hour less than wind; Hurricane.

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Saffir-Simpson scale 1

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Category 1: Winds 74 - 95 miles per hour and there will some damage.

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Saffir-Simpson scale 2

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Category 2. Winds 96 - 110 miles per hour and there will extensive damage.

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Saffir-Simpson Scale 3

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Category 3: Winds 111 - 130 miles per hour and there will be devastating damage.

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Saffir-Simpson Scale 4

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Category 4: Winds 131 - 155 miles per hour and there will be catastrophic damage.

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Saffir-Simpson Scale 5

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Category 5: Winds more than 155 miles per hour and there cill be catastophic damage.

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Saffir-Simpson Scale 6

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During 1924 - 2010, only 32 Atlantic basin hurricanes have been rated Category 5, and only a fraction of those have made landfall with that intensity.

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Saffir-Simpson 7

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In 2005, a record four hurricanes: Emily, Katrina, Rita, Wilma reached Category 5 intensity.

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Tropical cyclones 1

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A global perspective.

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Tropical cyclones 2

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The environement required for Tropical cyclones formations 1

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Sea surface temperature required must exceed 80 degrees F.

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The environments required for Tropical cyclones 2

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The surface layer of warm water in the ocean must be sufficiently deep, typically about 200 feet of more

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The environments required for Tropical cyclones 3

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The middle troposphere much cointain sufficient moisture.

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The environment required Tropical cyclones 4

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The wind in the atmosphere much not change substantially over height (weak vertical wind shear).

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The environment required Tropical cyclones 5

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The location must be at least least 5 degrees north or south of the equator.

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Hurricane Formation 1

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Trigger mechanisms for initial thunderstorms: Interstropical convergence zone.

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Hurricane Formation 2

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Trigger mechanisms for initial thuderstorms: Easterly waves in trade wind flow.

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Hurricane Formation 3

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Trigger mechanims for initial thunderstorms: Occlusion of extratropical cyclone over tropical waters.

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Hurricane Destruction 1

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Storm surge

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Hurricane destruction 2

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Winds

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Hurricane destruction 3

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Tornados

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Hurricanes destruction 4

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Inland Flooding

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Storm surge causes 1

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Onshore winds

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Storm surge causes 2

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Barometric effect

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Storm surge enhancing factors 1

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Wave height

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Storm surge enhacing factors 2

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Tides

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Storm enhancing factors 3

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Shape of coastline

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Hurricane spawned Tornadoes 1

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Hurricane Spawned Tornadoes 2

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Causes of cyclones Deaths

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