Weather InstrumentsWeather Instruments

How do they help in How do they help in predicting weather?predicting weather?

TemperatureTemperature

A meteorologist would use a thermometer to A meteorologist would use a thermometer to measure the local temperature.measure the local temperature.

Generally, there is a high temperature and Generally, there is a high temperature and low temperature predicted for each day. A low temperature predicted for each day. A

mathematical formula is used to help mathematical formula is used to help make these predictions as accurate as make these predictions as accurate as

possible. Also, a high and low possible. Also, a high and low temperature is recorded each day. The temperature is recorded each day. The low generally occurs in early morning low generally occurs in early morning

hours and the high in late afternoon hours.hours and the high in late afternoon hours.

ThermometerThermometerMeasures temperature

Scales used: degrees Fahrenheit (F) or degrees Celsius (C)

PrecipitationPrecipitation

Precipitation is collected in a rain Precipitation is collected in a rain gauge. It then tells a meteorologist gauge. It then tells a meteorologist how much it has rain or snowed in an how much it has rain or snowed in an area.area.

Rain GaugeRain GaugeMeasures amount of precipitation

Scale: collected in inches (in.) or centimeters (cm)

Air PressureAir Pressure

The difference in air pressure results in The difference in air pressure results in wind. Fronts then move as the wind wind. Fronts then move as the wind pushes them. Air will move from an area pushes them. Air will move from an area of high pressure to an area of low of high pressure to an area of low pressure. As winds blow into a low pressure. As winds blow into a low pressure area, air moves upward causing pressure area, air moves upward causing clouds to form leading to precipitation. In clouds to form leading to precipitation. In general, weather improves when pressure general, weather improves when pressure increases and worsens when pressure increases and worsens when pressure decreases. decreases.

BarometerBarometerMeasures Air Pressure

Scale: Inches

Some barometers use mercury (a liquid metal) and when the pressure pushes on the air in the tube of metal, the mercury will rise.

More commonly used today are aneroid barometers which do not have a tube of mercury but instead in a small box. The difference in air pressure causes this small box to change shape and move a needle on a gauge that indicates the air pressure. Normal air pressure is between 28 and 31 inches. Sudden changes in the air pressure means that the weather will be changing.

Barometer – measures air pressureBarometer – measures air pressure

HumidityHumidityHumidity is the amount of moisture in the air. As more water evaporates, the humidity gets greater.

Humidity is measured with a tool called a hygrometer.

HygrometerHygrometer

Measures: HumidityMeasures: Humidity Recorded in percents (%)Recorded in percents (%) 100 % humidity is raining; 10 – 30% humidity 100 % humidity is raining; 10 – 30% humidity

means it’s relatively drymeans it’s relatively dry

WindWind

Wind is simply just moving air. It moves Wind is simply just moving air. It moves because of a difference in air pressure or a because of a difference in air pressure or a difference in temperature. Wind direction difference in temperature. Wind direction and wind speed in measured in order for and wind speed in measured in order for meteorologists to determine the way a meteorologists to determine the way a front will move and how quickly it will it front will move and how quickly it will it will move. So, two instruments are used will move. So, two instruments are used to measure wind: wind vane and an to measure wind: wind vane and an anemometer. anemometer.

Wind VaneWind VaneDetermines wind direction – which way the wind is blowing from

Scale used: cardinal and intermediate directions

The pointer or the arrow

generally turns into the wind.

AnemometerAnemometerMeasures wind speed – how fast is the wind blowing

Scale used: knots or miles per hour

Beaufort Scale = used in measuring windBeaufort Scale = used in measuring windBeaufort Beaufort number number

Wind speed Wind speed MPH MPH Description Description  Sea conditions Sea conditions Land conditions  Land conditions 

00 <1<1 calmcalm flatflat calmcalm

11 1-31-3 light airlight air ripples without crestsripples without crests wind visible in smokewind visible in smoke

22 4-74-7 light breezelight breeze small waveletssmall wavelets leaves rustleleaves rustle

33 8-128-12 gentle breezegentle breeze large waveletslarge wavelets smaller twigs in smaller twigs in constant motionconstant motion

44 13-1813-18 moderate breezemoderate breeze small wavessmall waves small branches begin small branches begin to moveto move

55 19-2419-24 fresh breezefresh breeze moderate longer moderate longer waveswaves

small trees swaysmall trees sway

66 25-3125-31 strong breezestrong breeze large waves with foam large waves with foam crestscrests

large branches movelarge branches move

77 32-3832-38 near galenear gale sea heaps up and sea heaps up and foam begins to streakfoam begins to streak

whole trees in motionwhole trees in motion

88 39-4639-46 galegale moderately high moderately high waves with breaking waves with breaking

crestscrests

twigs broken from twigs broken from treestrees

99 47-5447-54 severe galesevere gale high waves with dense high waves with dense foamfoam

light structure damagelight structure damage

1010 55-6355-63 stormstorm very high waves; the very high waves; the sea surface is whitesea surface is white

trees uprooted; trees uprooted; considerable structure considerable structure

damagedamage

1111 64-7264-72 violent stormviolent storm except ally high wavesexcept ally high waves widespread structural widespread structural damagedamage

1212 73-8273-82 hurricanehurricane sea completely white sea completely white with driving spraywith driving spray

massive damage to massive damage to structuresstructures

Force 0

Force 1

Force 2

Force 3

Force 4

Force 5

Force 6

Force 7

Force 8

Force 9

Beaufort ScaleBeaufort Scale

Force 10

Beaufort ScaleBeaufort Scale

Force 11

Name that InstrumentName that Instrument

thermometerthermometer

wind vanewind vane

barometerbarometer

anemometeranemometer

rain gaugerain gauge