PrecipitationPrecipitation

PrecipitationPrecipitation

Any form of moisture Any form of moisture that falls from the skythat falls from the sky

The main forms areThe main forms are

RainRain SnowSnow SleetSleet HailHail

RainRain

Liquid precipitationLiquid precipitation Varies in sizeVaries in size Normal raindrops between 0.5 to 5 Normal raindrops between 0.5 to 5

mmmm Less that 0.5 mm drizzleLess that 0.5 mm drizzle

SnowSnow

May be May be Small pelletsSmall pellets Individual crystals Individual crystals

or or Crystals that Crystals that

combine to form combine to form snowflakessnowflakes

Large at temps Large at temps near 0 C and near 0 C and become smaller at become smaller at lower temperatureslower temperatures

SleetSleet

When snow falls When snow falls through a layer of through a layer of freezing air near freezing air near the surfacethe surface

Damaging PrecipitationDamaging Precipitation

http://www.chaseday.com/hailfall.htm

HailHail

Solid precipitation Solid precipitation in lumps of icein lumps of ice

Spherical or Spherical or lumpslumps

Forms in Forms in cumulonimbus cumulonimbus cloudsclouds

                      

Remember Convection!!!!Remember Convection!!!!

Hot, less dense Hot, less dense air risesair rises

Requires daytime Requires daytime heatingheating

Patches of Patches of sunlight helpsunlight help

Updrafts (in red) rise as ground surface is heated by

the sun above ambient air temperatures (blue).

Formation of HailFormation of Hail

Hail FormationHail Formation Hail stones form by Hail stones form by

accretionaccretion Small hail gets caught up in Small hail gets caught up in

the updraft and goes to the the updraft and goes to the top of the cloud where it top of the cloud where it receives another receives another layer of layer of iceice

This repeats until the hail This repeats until the hail cannot be supported by cannot be supported by the updraftthe updraft and it falls and it falls

                 

Hail Hail requiresrequires strong updrafts to formstrong updrafts to form

For the smallest hail to For the smallest hail to form, an updraft of form, an updraft of around 36 to 54 km/h (24-around 36 to 54 km/h (24-34 mph) is required. 34 mph) is required.

golf-ball sizegolf-ball size (1 3/4 inch (1 3/4 inch diameter) -- require diameter) -- require updrafts of around 88 updrafts of around 88 km/h (55 mph) to form.km/h (55 mph) to form.

Softball-sizeSoftball-size hail involves hail involves updrafts exceeding 160 updrafts exceeding 160 km/h (100 mph).km/h (100 mph).

““like driving on ball like driving on ball bearings”bearings”

http://www.chaseday.com/hailfall.htm

Record HailRecord Hail Record hail fell in Record hail fell in

Coffeyville, KSCoffeyville, KS diameter 14.4 diameter 14.4

cm (5.67 cm (5.67 inches)inches)

Credit: NOAA Photo Library

Punching the corePunching the core

Hail SizesHail Sizes PeaPea6.4 millimeters (0.25 in)6.4 millimeters (0.25 in) DimeDime17.9 millimeters (0.70 in)17.9 millimeters (0.70 in) PennyPenny19 millimeters (0.75 in)19 millimeters (0.75 in) NickelNickel21.2 millimeters (0.83 in)21.2 millimeters (0.83 in) QuarterQuarter24.26 millimeters 24.26 millimeters

(0.955 in)(0.955 in) Half dollarHalf dollar30.6 millimeters 30.6 millimeters

(1.20 in)(1.20 in) WalnutWalnut38 millimeters (1.5 in)38 millimeters (1.5 in) GolfballGolfball44 millimeters (1.7 in)44 millimeters (1.7 in) Tennis BallTennis Ball64 millimeters 64 millimeters

(2.5 in)(2.5 in) BaseballBaseball70 millimeters (2.8 in)70 millimeters (2.8 in) Grapefruit108 millimeters Grapefruit108 millimeters

(4.3 in)(4.3 in) Softball114 millimeters (4.5 in)Softball114 millimeters (4.5 in)

Measuring Precipitation Measuring Precipitation

A Rain gauge is A Rain gauge is used to measure used to measure liquid liquid precipitationprecipitation

Doppler RadarDoppler Radar

Doppler radar is a Doppler radar is a key forecasting key forecasting tooltool

Based on the Based on the Doppler principle Doppler principle also used with also used with light and soundlight and sound

All weather radars send out radio All weather radars send out radio waves from an antenna.waves from an antenna.Objects in the air, Objects in the air,

such as raindrops, such as raindrops, snow crystals, snow crystals, hailstones or even hailstones or even insects and dust, insects and dust, scatter or reflect scatter or reflect some of the radio some of the radio waves back to the waves back to the antenna. antenna.

All weather radars, All weather radars, including Doppler, including Doppler, electronically convert the electronically convert the reflected radio waves into reflected radio waves into pictures showing the pictures showing the location and intensity of location and intensity of precipitation. precipitation.

By Jack Williams, By Jack Williams, USATODAY.com USATODAY.com

Remember the meteorologist saying the wind Remember the meteorologist saying the wind is blowing towards or away from the radaris blowing towards or away from the radar

Used to indicate rotation in a thunderstorm Used to indicate rotation in a thunderstorm which could indicate a tornado formingwhich could indicate a tornado forming