Types of Precipitation Precipitation comes in three forms Precipitation comes in three forms Liquid – rain, drizzle Liquid – rain, drizzle Freezing – freezing rain, freezing drizzle Freezing – freezing rain, freezing drizzle Frozen – snow Frozen – snow snow pellets snow pellets snow grains snow grains ice pellets ice pellets hail hail The vertical temperature structure of the atmosphere determines whether liquid or solid precipitation will fall. The vertical temperature structure of the atmosphere determines whether liquid or solid precipitation will fall.

Rain ► Rain is composed of liquid drops with a diameter of 0.5 mm to 6 mm. ► Most rain begins as snow high in the atmosphere that melts in the warmer air of the lower atmosphere to fall as rain. ► Raindrops resemble flattened spheres not teardrops.

Rain Intensity  widely spaced drops do not completely wet ground  Very Light: widely spaced drops do not completely wet ground  : produces trace to 0.10 inches/hour  Light: produces trace to 0.10 inches/hour  : produces 0.11 – 0.30 inches/hour  Moderate: produces 0.11 – 0.30 inches/hour  : produces over 0.30 inches/hour  Heavy: produces over 0.30 inches/hour

Flash Floods a rapid rise of water along a stream or low- lying urban area occur within 6 hours of a significant rain event usually caused by intense storms that produce heavy rainfall in a short time very strong - can roll boulders, uproot trees, scour out new channels, and destroy buildings and bridges

On April 15, 2007, between 5 and 10 inches of rain fell in NJ

Route 18

Flooding and the Coast

Drizzle ► liquid drops with diameters between 0.2 and 0.5 mm ► because there are many more drops in a shower of drizzle than in a shower of light rain, drizzle reduces visibility more than light rain does

Drizzle and Rain

Heavy Drizzle vs. Heavy Rain

Freezing Rain or Freezing Drizzle liquid drops that fall into a layer of below freezing air close to the ground and freeze on contact liquid drops that fall into a layer of below freezing air close to the ground and freeze on contact glaze surfaces with a coating of ice glaze surfaces with a coating of ice create hazardous walking and driving conditions and can weigh down tree limbs and power lines so that they break create hazardous walking and driving conditions and can weigh down tree limbs and power lines so that they break do not bounce when hit the ground do not bounce when hit the ground

Freezing Rain

Freezing rain is dangerous.

SNOW solid, white or translucent ice crystals mainly branching in hexagonal forms most precipitation forms as snow

AMAZING MICROSCOPIC TIMELAPSE OF A SNOWFLAKE - YOUTUBE

Snowfall Intensity Very Light: Scattered flakes do not completely wet or cover the ground Light: visibility is 5/8 of a mile or more Moderate: visibility is less than 5/8 mile but not less than 5/16 of a mile Heavy: visibility is less than 5/16 of a mile

Snow

Heavy snow

Hartford CT - Snow Storm Timelapse - YouTube Time Lapse of Snow Fall in Hartford, Connecticut in 2013

Time Lapse of Snowfall in Belmar, NJ 2010 Time lapse of 2010 Snow Storm - YouTube

Snow Shoveling Time lapse snow shoveling. - YouTube

Snow vs Water Rule of Thumb: one foot of snow is = to one inch of water But this number is highly variable and strongly dependent on temperature. above freezing: 6” snow = 1” rain called wet snow around 30 F: 10” snow = 1” rain 10 F: 18” – 24” = 1” called dry snow or powder snow

Snow Pellets (soft hail or graupel) white, opaque, cone shaped or nearly round ice particles similar to snow in structure formed when ice crystals fall through layers of cold water droplets that stick to its surface ranges in size from 2 to 5 mm in diameter often falls in a shower before or with snow when surface temperatures are very near freezing

Small Snow Pellets

Large Snow Pellets

Snow Grains also known as granular snow very small, white, flat, elongated, opaque particles of ice diameters less than 1 mm never fall in showers fall in small quantities from stratus clouds or from fog always freeze prior to hitting ground

Ice Pellets or Sleet consists of spherical or irregularly shaped transparent or translucent pellets of ice less than 5 mm in diameter form when snowflakes fall through an above-freezing layer of air under the cloud and partially melt and then fall through subfreezing air and refreeze before reaching the ground pellets bounce off of surfaces on contact Ice Pellets falling from the sky - YouTube

Sleet

HAIL ► round or irregular lumps of ice produced by convective clouds (cumulonimbus) ► most hailstones are less than 1.0 cm in diameter ► hailstones larger than 2 cm in diameter is one criteria for to designate a thunderstorm as severe ► can reach size of grapefruits ► cause significant damage to property, particularly crops

How Hail Forms ► in thunderstorms that have tremendous updrafts and down drafts ► hailstones begin as tiny ice crystals that grow in size by accretion (adding layer after layer of ice) as they are thrown into water droplets in the storm ► storm updrafts suspend hailstones until they are too large and fall

Huge Hail

Hail Damage

Hail Storm Oklahoma City - YouTube

What is the opposite of precipitation?

Drought. Almaden Reservoir, San Jose, CA January 2014

The small city of Montague, which is located in north central California, "risks running out of drinking water by the end of summer.” 100% of CA is experiencing "moderate" to "exceptional" drought. 77% is experiencing "extreme" to "exceptional" drought, which are the two most severe categories.

NJ Water Supply Drought Indicators htindicators.pdf