Lecture 15Outline of Last Lecture I. ReviewII. Upper-Air Troughs and Surface LowsIII. Review IV. Stages of Mid-Latitude Cyclone DevelopmentV. CyclogenesisVI. Where do cyclones form?VII. Rocky MountainsVIII. Mid-Latitude Cyclone LifeIX. Review: Heights and TemperaturesX. Mid-Latitude Cyclone TracksOutline of Current Lecture XI. Scales and LifespanXII. How is Forecast Made?XIII. Sources of DataXIV. Surface Station NetworkXV.Rawinsonde NetworkXVI. Satellite ImageryXVII. RadarXVIII. The National Weather ServiceXIX. WatchesXX.WarningsATMS 100 1st EditionXXI. Watches, Warnings, and AdvisoriesXXII. Weather ForecastingXXIII. Review of FrontsXXIV. Computer ModelsXXV. Weather ModelingXXVI. Numerical Weather PredictionCurrent LectureXXVII. Scales and Lifespana. The larger atmospheric phenomenon is the longer it lasts, the more predictable it isb. Scale:i. small turbulent eddiesii. thunderstorms, tornadoes, waterspouts,dust devilsiii. land/sea breeze, mountain/valley breeze, chinook wind, santa ana windiv. hurricane, tropical stormsv. weather map features, high/low pressure areas, weather frontsvi. longwaves in the westerliesXXVIII. How is Forecast Made?b. Gather Datai. satelittes, radar, station data, soundings, etc.c. Analyze Datai. Why is the weather doing what it is doing?ii. Why is it raining?d. Issue forecast based on analysisi. How and why do I expect the weather to change?XXIX. Sources of Datab. Surface Weather Stationsi. airports, ships, buoys, etc.ii. hourlyc. Rawinsondes (weather balloons)i. Twice daily (00Z and 12Z)d. Satellite e. RadarXXX. Surface Station Networkb. Various points around the worldi. concentrated at airportsc. not equally spacedi. tend to be where more people liveXXXI. Rawinsonde Networkb. Upper-air observing networkc. more sparcei. one or two weather balloons per state twice per day1. Indiana has no weather Balloon launches2. 1 in missouriXXXII. Satellite Imageryb. Visible Satellite: detects reflected sunlight (from clouds) i. Does not work at nightii. thick clouds white, thin clouds grayiii. can see texture and shadowsc. IR Satellite: detects infrared radition i. Works 24 hours a day1. IR radiation emitted depends on temperature2. Low clouds appear gray, high clouds appear whited. Water Vapor Satellite: Detects IR radiation emitted by water vapori. senses water vapor even where there are no cloudsii. upper troposhpere only1. cannot sense water vapor near groundiii. dry=dark/red/orangeiv. moist=purple/blueXXXIII. The National Weather Serviceb. In the US, the National Weather Service (NWS) is responsible for the collection and dissemination of all weather datac. Branch of US governmentd. Issues officlal forecasts, watches, warnings, and advisories for threat-ening weather conditionsXXXIV. Watchesb. A watch means that a certain type of hazardous weather (severe thun-derstorms, tornadoes, heavy snow) is possiblec. Example: a tornado watch means increased chance of tornadoes over next several hoursd. severe thunderstorm watchXXXV. Warningsb. A warning means that hazardous weather is occurringi. observed or detected by radarc. a severe thunderstorm or tornado warning means to take shelter im-mediatelyd. warnings usually last for less than an houri. except blizzards, etc.XXXVI. Watches, Warnings, and Advisoriesb. watch means increased risk of hazardous weatheri. specific location (large part of state) and time period (several hours)c. warning means hazardous weather is imminent or occurringd. advisories issues for less hazardous conditionsXXXVII. Weather Forecastingb. Simple Method: Moving things alongi. assume weather features (lows, fronts, rain, etc.) continue to move, unchanged in the direction they are movingii. can provide a good first guess at weather for the next 24 hoursc. Can also run the same model several times to produce an ensemble offorecastsi. better captures variability and uncertainty ii. atmosphere is chaoticd. Statistical methodse. computer models are NOT and never would be perfecti. forecasts continue to imporveXXXVIII. Review of Frontsb. Cold Front:i. leading edge of advancing cold airii. temps drop as front passesc. Warm Fronts:i. back edge of retreating cold air massii. temps increase as front passesXXXIX. Computer Modelsb. Atmospheric motions described by complicated set of equationsi. can’t solve them by hand even with 3 semesters of calculusc. What to do? Use a computerd. Supercomputeri. thousands of CPUSXL. Weather Modelingb. Weather observations from all over the world are assimilated by super-computersc. there is inherent uncertainty and error in these observationsd. there are regions without many observationsi. especailly over the oceane. Observations interpolated to a regular 3D grid of pointsi. some models only cover USii. some cover entire worldf. Computer generates analysis current conditionsXLI. Numerical Weather Predictionb. Numerical models solves atmospheric equations at each grid point nadproduces a forecasec. Different models have different grid spacingsi. finer grid spacing (resolution) does not necissarily make models more accurateii. model is able to capture smaller-scale featuresXLII. TV Forecastersb. don’t wear greenin front of a green screen or blue in front of a blue