Weather InstrumentsP 611-614

We need data to forecast the weather Temperature Air pressure Humidity Type of clouds Level of precipitation Wind direction and speed

Instruments used to gather the data Lower Atmospheric ConditionsTemperature

Thermometer• Uses a liquid either mercury or alcohol

sealed in a glass tube Electrical thermometer

• As temp rises the electrical current increases

• A thermistor responds very quickly and is used where temps change quickly

Air pressure Barometer Aneroid (pictured) Mercury

fronts are usually indicated by a drop in air pressure

Wind Speed and direction Anemometer

Wind speed Wind vane

Wind direction

Rainfall Rain gauge

Measuring Upper Atmospheric Conditions

Doppler image of a hurricane

RadarStands for radio

detection and ranging Uses reflected radio

wavesDoppler radar Can indicate precise

location, intensity of precip and extent of a storm

Shows wind patterns Towards or away

from the radar

Radiosonde An instrument

package that is carried by a helium-filled balloon

Radio sends info to ground

Determines direction and speed of high altitude winds

Skew-T Shows a vertical

slice of the atmosphere

Temperature on right Dew point on left Air pressure Wind speed and

direction

Weather SatellitesCan measure visible Infrared Ocean conditions

temperature and flow of ocean currents and

height of ocean waves

Computers Solve

mathematical equations that describe the behavior of the atmosphere

Can store weather data

Can store weather records

This info is reported from stations WMO World Meteorological

Organization 10,000 land based stations and

hundreds of ship-based stations Weather satellites GOES Global Orbiting Earth Satellite

Data from stations is compiled and analyzed to forecast In the past this was done by hand Now much is done by computer But, different programs work better

for different locations and types of weather

Often two or three computer models are consulted to make one forecast

Weather Station Symbols Temperature is

upper left corner Barometric (air)

pressure is upper right

Air pressure represents the last

three digits of the observed pressure reading in millibars (mb)

Like on previous labs

Dew point Dew Point is lower left

corner When the air

temperature and the dew point are the same the air is saturated

Relative humidity can be inferred High if temp and dp are

close Low if large difference

between dp and temp

Relative Humidity can be inferred When the air and dew point

temperatures are very close, this indicates that the air has a high relative humidity.

The opposite is true when there is a large difference between air and dew point temperatures, which points to air with a low relative humidity.

Wind Speed and Direction Wind stick points

in the direction "from" which the wind is blowing

Which direction is the wind from?

Wind Speed May be measured

in mph, km/hr or knots

The more barbs the windier it is

Each long barb is approx 10 knots

Cloud Cover

Precipitation Symbols

WorksheetsSurface Weather Map Study the tables and the station

model Use the info to answer the questions

Transparency worksheets Study the tables and the station

model Use the info to answer the questions

Dry Line Note the sharp

difference in dew points

The line that separates dry air from moist air

Isobars Lines that connect

points with equal air pressure

Drawn at 4 mb (millibar) intervals

Pressure and Wind Relationships Draw isobars Use pencil CI = 4 Mark high and

low pressure Answer the

questions

Methods of Forecasting Persistence Trend Analog

Persistence Persistence—

based on continuity of a weather pattern—if it is raining now it will probably be raining tomorrow

Trend Trend—based on

the movement or trend of the weather system Ex. Cold front moving E at 20 Km/hr will affect weather 80 KM away in 4 hours

Happy Birthday, Hoang

AnalogOthers Climatology—data

accumulated through many years 4th of July is usually hot

and dry Numerical Weather

Prediction—uses programs built by meteorologists Not exact

compares present weather (cloud cover, wind, temperature, humidity, etc) with weather conditions produced by same features in the past

MeteorologistsWhat high school courses are

necessary to prepare for a career in meteorology?

Because meteorology is a science, a good background in mathematics and the sciences is mandatory. Knowledge of physics and chemistry is helpful toward a career in the atmospheric sciences.

OU is the Best for Meteorology

Weather Station Symbols Temperature is

upper left corner Barometric (air)

pressure is upper right

Lab Do isotherms in red (every 2)

Do lightly in pencil first Do isobars in blue (Every4)

Do lightly in pencil first

Winds

Three causes of motion(recap)

1. Warm air rises and cool air sinks because of density This is called a convection current

2.pressure differences in the atmosphere that are a result of temperature differences Wind is horizontal air movement

3. The deflection of objects to the right in the northern hemisphere—called the Coriolis Effect Due to rotation of the earth

Winds blow from high to low pressure.

Highs and Lows? Winds circle

Clockwise around a high

Highs generally mean cold dry air that is sinking

High pressure usually = fair weather

Low Pressure Systems Winds circle

counterclockwise around a low

Warmer air rises and cools and forms clouds and precipitation

Low pressure usually = rainy weather

Global Circulation Patterns We are located

in the Westerlies section

That means our weather moves from the west coast to the east coast

Overall movement is west to east

Local wind patterns can be from any direction

Recognizing fronts on a map

sharp temperature changes over relatively short distances

changes in the moisture content of the air (dew point)

shifts in wind direction low pressure troughs

and pressure changes clouds and

precipitation patterns

Types of fronts Named for the

invader Each type of front

has a typical weather scenario

Cold Front heavy cold air

displaces lighter warm air, pushing it upward

Cumulus clouds form and usually grow into thunderstorms

Temperatures drop anywhere from 5 to 15.

Winds become gusty and erratic.

Rain, snow, sleet, and hail can occur with a cold front.

Warm Front Warm fronts occur

when warm air replaces cold air by sliding over it.

Altocumulus clouds form and may be associated with rain, snow, or sleet.

Temperatures may warm slightly.

Winds are usually gentle with this kind of front.

Stationary Front neither warm nor cold

air advances. The two air masses reach a stalemate. That is what stationary

means - that neither front is moving.

can last for days, producing nothing but Altocumulus clouds

Temperatures remain stagnant and winds are gentle to nil

Occluded Front cold air is replacing

cool air or vice versa at the surface, with warm air above.

Both types of fronts are usually associated with rain or snow and cumulus clouds.

Temperature fluctuations are small and winds are gentle.

Where are the fronts?Stationary front Change in wind

direction Can dump heavy

rains

Warm Front Marked

temperature difference

Cold front Cold temperatures

are moving in

Wind and Pressure Relationship Lab

Remember Topographic Maps?

Same Concept—Different Use

Isotherm=equal temperature

Isobar=equal barometric pressure

contour interval (CI)1. The contour intervals

vary

2. Isobars often have an interval of 4

3. Read the directions or look at examples to see the contour level

Iso therm Equal temperature If a station reports

the exact value the line will go through the station symbol

If it is not exactly on the value it will not

Points shown are reporting stations Here, the stations

reported pressure and temperature

The lines are drawn in different colors to help differentiate them

There may be areas that do not report or have no station

The closer contour lines are to one another, the higher the wind speed.

Where is the wind speed high? Where is it low?

Inside a series of closed contours (the contours make a circle) is a High or Low pressure

Describe the motion of the wind.

Wind Flow around Isobars Winds flow

roughly parallel to the isobars, as depicted in the schematic below

Current Weather Conditions

Current Weather Station Data

Source:University of Illinois http://ww2010.atm

os.uiuc.edu/(Gh)/home.rxml

Metars In a small group try to figure out

what each set of numbers or letter mean

TYPEIDTIMEWINDVISWXSKYT/TDALTREMARKMETAR KORD 041656Z 19020G26KT 6SM -SHRA BKN070 12/08 A3016 RMK AO2

Understanding MetarsActivity Brainstorm about

what the numbers and letters may mean

Discuss as a class Interpret metars and

decode them

Zulu Time Used to be known as Greenwich

Mean Time Uses the military clock of 24 hours For numbers above 13 subtract 12

Converting to KS time For CST –6 For CDT -5

Upper Air Data Shows

Become a meteorologist OU is the best