Precipitation ● Key questions ○ (1) What are the different types of precipitation ○ (2) how does precipitation form ○ (3) how do we actually measure precipitation ● Condensation Nuclei because they are ___hydroscopic ○ (conversely, __ hyrdrophobic particles do not adsorb water vapor) CN RH condensation and activated (Cloud condensation nuclei) (Collision and coalescence) → terminal velocity Ice processes → homogeneous freezing → supercool __liquid water droplets__ → heterogeneous freezing Condensation nuclei is soluble Three nuclei slide Deposition_______ Immersion freezing___ Contact freezing _____ Ice processes slide Aggregation Snowflakes Rimed ice Types: - Rain - Virga - Graupel (rimed ice) - Snow - Hail - Sleet - Freezing rain Thunderstorm forcing mechanisms 1.) Topography 2.) Unequal surface heating 3.) Converging surface winds 4.) Fronts 5.) Turbulence 6.) Divergence aloft If cold enough and snowing, we call this _____thunder snow_____ Thunderstorms: Ordinary (single-cell) thunderstorms Multicellular thunderstorms Supercell thunderstorms There storms often form due to low level convergence of the winds These storms exhibit three stages: 1.) Cumulus stage 2.) Mature stage 3.) Dissipating stage ___down draft___ __gust front__ __overshooting top__ Shelf__ cloud Roll __ cloud Supercells and Tornadoes ● Supercells form in regions with strong updrafts and strong vertical wind shear ○ Characterized by: ■ Very strong updrafts ■ Damaging surface winds ■ Large tornadoes ■ Large hail ■ Deep and wide clouds ● CL - classic supercell ● HP - high precipitation supercell ● LP - low precipitation supercell ● A vortex tube is a spinning cylinder created by a mesocyclone Tornadoes mescyclone is usually 3 miles long, but when it becomes a tornado, it is stretched vertically and the winds become stronger, and create a tornado vortex L;asdj; Lightning Notes ● Lightning is a discharge of electricity between two oppositely charged regions/objects that usually occurs in mature thunderstorms ● Four main types: ○ In cloud ○ Cloud to cloud ○ Cloud to air ○ Cloud to ground ● In-cloud lightning is 65% of all lightning ● Cloud to ground lightning is ~35% of all lightning Where do cyclones form (US) 1.) Colorado low 2.) Nor’easter 3.) Hatteras low 4.) Alberta clipper - If your Upper level divergence is more impactful than lower level divergence then the system is going to strengthen Summary Slide For Cyclones (Mid latitude) - Wind flow (counterclockwise and inward) - Strongest winds (aloft) - Lowest pressure (in the center at the surface) - Vertical structure (wind increase with height and converge at surface, diverge aloft) - Air in center (rising) - Weather fronts (present) - Energy source (fronts, temperature gradients) Hurricanes; ● Form in the tropics ● Characteristics of the tropics include: ○ High noon sun ○ Hugh relative humidity ○ Little variation in surface pressure ● Different names: ○ Hurricane ■ Forms over tropics ○ Typhoon ■ Forms over North Pacific ○ Cyclone ■ Over the Indian Ocean ○ Tropical Cyclone ■ Vicinity of Australia ● Spiral Rain Bands ○ Banding precipitation around the center of the storm ● Eyewall ○ Ring of intense thunderstorms that rotate around the center of the storm ● Hurricane triggers can be ○ Along the Intertropical Convergence Zone ○ Eastern side of a tropical wave ○ Along a pre-existing disturbance ● Factors that don’t lead to formation ○ Trade wind inversion ○ Strong upper-level winds, which result in strong vertical wind shear ● Sometimes a new eyewall will form that overtakes the original, known as an eyewall replacement ● What can cause a hurricane to weaken ○ Landfall ○ Cold water ○ Wind shear ○ An area with shallow warm water