2We need data to forecast the weather TemperatureAir pressureHumidityType of cloudsLevel of precipitationWind direction and speed
3Instruments used to gather the data Lower Atmospheric ConditionsTemperatureThermometerUses a liquid either mercury or alcohol sealed in a glass tubeElectrical thermometerAs temp rises the electrical current increasesA thermistor responds very quickly and is used where temps change quickly
4Air pressure Barometer Aneroid (pictured) Mercury fronts are usually indicated by a drop in air pressure
5Wind Speed and direction AnemometerWind speedWind vaneWind direction
9Radar Doppler radar Stands for radio detection and ranging Uses reflected radio wavesDoppler radarCan indicate precise location, intensity of precip and extent of a stormShows wind patternsTowards or away from the radar
10RadiosondeAn instrument package that is carried by a helium-filled balloonRadio sends info to groundDetermines direction and speed of high altitude winds
14Weather Satellites Can measure visible Infrared Ocean conditions temperature and flow of ocean currents andheight of ocean waves
15ComputersSolve mathematical equations that describe the behavior of the atmosphereCan store weather dataCan store weather records
16This info is reported from stations WMO World Meteorological Organization10,000 land based stations and hundreds of ship-based stationsWeather satellitesGOES Global Orbiting Earth Satellite
17Data from stations is compiled and analyzed to forecast In the past this was done by handNow much is done by computerBut, different programs work better for different locations and types of weatherOften two or three computer models are consulted to make one forecast
18Weather Station Symbols Temperature is upper left cornerBarometric (air) pressure is upper right
19Air pressurerepresents the last three digits of the observed pressure reading in millibars (mb)Like on previous labs
20Dew point Dew Point is lower left corner When the air temperature and the dew point are the same the air is saturatedRelative humidity can be inferredHigh if temp and dp are closeLow if large difference between dp and temp
21Relative 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.
22Wind Speed and Direction Wind stick points in the direction "from" which the wind is blowingWhich direction is the wind from?
23Wind Speed May be measured in mph, km/hr or knots The more barbs the windier it isEach long barb is approx 10 knots
35Analogcompares present weather (cloud cover, wind, temperature, humidity, etc) with weather conditions produced by same features in the pastOthersClimatology—data accumulated through many years4th of July is usually hot and dryNumerical Weather Prediction—uses programs built by meteorologistsNot exact
36MeteorologistsWhat 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.
41Three causes of motion(recap) WIND ALWAYS FLOWSFROM HIGH TO LOW PRESSURE1. Warm air rises and cool air sinks because of densityThis is called a convection current2.pressure differences in the atmosphere that are a result of temperature differencesWind is horizontal air movement3. The deflection of objects to the right in the northern hemisphere—called the Coriolis EffectDue to rotation of the earth
43Highs and Lows? Winds circle Clockwise around a high Highs generally mean cold dry air that is sinkingHigh pressure usually = fair weather
44Low Pressure Systems Winds circle counterclockwise around a low Warmer air rises and cools and forms clouds and precipitationLow pressure usually = rainy weather
45Global Circulation Patterns We are located in the Westerlies sectionThat means our weather moves from the west coast to the east coast
46Overall movement is west to east Local wind patterns can be from any direction
47Recognizing fronts on a map sharp temperature changes over relatively short distanceschanges in the moisture content of the air (dew point)shifts in wind directionlow pressure troughs and pressure changesclouds and precipitation patterns
48Types of fronts Named for the invader Each type of front has a typical weather scenario
49Cold Frontheavy cold air displaces lighter warm air, pushing it upwardCumulus clouds form and usually grow into thunderstormsTemperatures drop anywhere from 5 to 15.Winds become gusty and erratic.Rain, snow, sleet, and hail can occur with a cold front.
50Warm FrontWarm 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.
51Stationary Frontneither 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 cloudsTemperatures remain stagnant and winds are gentle to nil
52Occluded Frontcold 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.
53Where are the fronts? Stationary front Change in wind direction Can dump heavy rains
58Same Concept—Different Use Isotherm=equal temperatureIsobar=equal barometric pressure
59contour interval (CI) The contour intervals vary Isobars often have an interval of 4Read the directions or look at examples to see the contour level
60Iso therm Equal temperature If a station reports the exact value the line will go through the station symbolIf it is not exactly on the value it will not
61Points shown are reporting stations Here, the stations reported pressure and temperatureThe lines are drawn in different colors to help differentiate themThere may be areas that do not report or have no station
62The closer contour lines are to one another, the higher the wind speed.