Meteorology: Part 2Meteorology: Part 2Weather MapsWeather Maps

EckertEckert

Minerva DeLand ScienceMinerva DeLand Science

Partner DiscussionPartner Discussion

What are some variables shown on a What are some variables shown on a weather map? Be specific.weather map? Be specific.

On a Weather Map…On a Weather Map…

Weather Station ModelsWeather Station Models• Covered in Meteorology Part 1Covered in Meteorology Part 1• See ESRT pg 13 for an exampleSee ESRT pg 13 for an example

Picture from: http://weather.about.com/od/forecastingtechniques/ss/mapsymbols_8.htm

Weather StationsWeather Stations

% cloud cover% cloud cover– Shown on a station model when Shown on a station model when part of part of

the circle is shadedthe circle is shaded– Sometimes shown on a map by Sometimes shown on a map by shadingshading

IsolinesIsolines

• Lines that connect points of equal Lines that connect points of equal valuevalue

An isoline map is drawn to show any change An isoline map is drawn to show any change over a certain area or fieldover a certain area or field

• 1. Isolines 1. Isolines NEVERNEVER cross each other cross each other Ex: one spot has two Ex: one spot has two temperatures?temperatures?

20°

30 °

40 ° 50 ° 60 °

X

YZ

Isoline Rules

2. Isolines are generally parallel2. Isolines are generally parallel

Isoline RulesIsoline Rules

3. Isolines are continuous – they make 3. Isolines are continuous – they make circles or run off the map.circles or run off the map.

Isoline rulesIsoline rules

IsothermsIsotherms

• Lines connecting points of equal Lines connecting points of equal temperature.temperature.

http://earth.usc.edu/~stott/Catalina/images/tempdist.images/isotherms.jpg

IsobarsIsobars

• Lines on a weather map connecting Lines on a weather map connecting points of equal barometric pressure.points of equal barometric pressure.

• Usually 4 mb incrementsUsually 4 mb increments

http://vathena.arc.nasa.gov/curric/weather/hsweathr/isomap4.gif

GradientGradient

• The gradient formula is in the ESRT pg The gradient formula is in the ESRT pg 11• The The field valuefield value means whatever the surface is means whatever the surface is

that you are measuring (elevation, depth, that you are measuring (elevation, depth, thickness, etc)thickness, etc)

• Distance is the measured distance between two Distance is the measured distance between two pointspoints

Gradientvalue

dis c e

tan

• A A steep (high)steep (high) gradient changes gradient changes quickly and the isolines are close quickly and the isolines are close together.together.

• A A gentle (low)gentle (low) gradient changes slowly gradient changes slowly and the lines are far apart.and the lines are far apart.

Steep area

Gentle area

WindWind

• Horizontal movement of air over Horizontal movement of air over Earth’s surfaceEarth’s surface

• Shown on weather map with Shown on weather map with arrowsarrows and and feathersfeathers– See ESRT page 13See ESRT page 13

What causes wind?What causes wind?

• Difference in temperature and Difference in temperature and pressurepressure

• Wind always blows from high to low Wind always blows from high to low pressurepressure

Coriolis EffectCoriolis Effect

• Caused by Earth’s rotationCaused by Earth’s rotation• Deflects windsDeflects winds

– Curves winds to the right in the northern Curves winds to the right in the northern hemispherehemisphere

• A north wind is deflected to the A north wind is deflected to the WestWest• East wind is deflected to the East wind is deflected to the North

http://nsidc.org/arcticmet/images/factors/coriolis.gif

Winds Huge Convection CellWinds Huge Convection Cell

Draw a huge convection cell…Draw a huge convection cell…

Relationship of wind speed and Relationship of wind speed and pressure gradientpressure gradient

• Closer isobars means great change in Closer isobars means great change in pressurepressure

• Closer isobars means faster wind Closer isobars means faster wind speedspeed

Low Pressure SystemsLow Pressure Systems

• Temperature…warmerTemperature…warmer• Wind circulation…counterclockwise; Wind circulation…counterclockwise;

inward; risinginward; rising

http://www.usatoday.com/weather/tg/wlowpres/wlowpres.htm

Low Pressure Systems Low Pressure Systems

• Cloud Cloud development…development…humid; cloudyhumid; cloudy

• Precipitation…Precipitation…good chance of good chance of precipitation precipitation

http://www.uwsp.edu/gEo/faculty/ritter/images/atmosphere/pressure_wind/high_pressure_small.jpg

High Pressure SystemsHigh Pressure Systems

• Temperature…coolerTemperature…cooler• Wind circulation…clockwise; Wind circulation…clockwise;

outward; fallingoutward; falling

http://www.usatoday.com/weather/tg/wlowpres/wlowpres.htm

High Pressure SystemsHigh Pressure Systems

• Cloud development…Cloud development…clear; no cloudsclear; no clouds

• Precipitation…no Precipitation…no precipitationprecipitation

http://www.uwsp.edu/gEo/faculty/ritter/images/atmosphere/pressure_wind/high_pressure_small.jpg

Partner DiscussionPartner Discussion

• If the wind blows weather from a If the wind blows weather from a higher latitude what will probably higher latitude what will probably happen to our temperatures? happen to our temperatures?

• Lower Latitude?Lower Latitude?

H LWind moves from High to Low or Low to High Air Pressure?

BUT, will the wind have a straight path between High and Low?

Why or Why Not?

LWhich way will Air rotate, as it

rushes into a Low Pressure area?

HWhich way will Air rotate, as it rushes

away from a High Pressure area?

L

Will Surface Winds converge or diverge at Low Pressure Area?

Ground Level

H

Will Surface Winds converge or diverge at High Pressure Area?

Ground Level

Air Masses and place of originAir Masses and place of origin

• Air mass – huge region of air with Air mass – huge region of air with similar temperature and humiditysimilar temperature and humidity

• Source region – place where air mass Source region – place where air mass originates originates

Air Mass animationAir Mass animation

• Air Mass AnimationAir Mass Animation

Air Mass Source RegionsAir Mass Source Regions

http://members.aol.com/pakulda/images/stpptam.gif

Fill in chart in note packetFill in chart in note packet

FrontsFronts

• Boundary between two air massesBoundary between two air masses

Cold frontCold front

• Leading edge of a cold air massLeading edge of a cold air mass• Moves quickly (25-35 mph)Moves quickly (25-35 mph)• Rounded edge because cold dense Rounded edge because cold dense

air is trying to go beneath warm airair is trying to go beneath warm air

What weather is associated with a What weather is associated with a cold cold frontfront??

Violent storms followed by cold weather Violent storms followed by cold weather often result when a cold front moves in. often result when a cold front moves in. Cold dense air quickly pushes up the warm Cold dense air quickly pushes up the warm air. The warm air cools and moisture air. The warm air cools and moisture quickly condenses, forming storms. quickly condenses, forming storms.

Cold frontCold front

Behind frontBehind front• Clear, dry airClear, dry air• High pressureHigh pressure• Cool temps.Cool temps.

Cold FrontCold Front

At FrontAt Front• Cumulus cloudsCumulus clouds• Winds gust because warm air is Winds gust because warm air is

forced upforced up• Pressure dropsPressure drops• Brief, heavy rain/thunderstormsBrief, heavy rain/thunderstorms

Cold frontCold front

Ahead of the FrontAhead of the Front• Warm airWarm air• Humid airHumid air

ThunderstormsThunderstorms

• Usually associated with a cold frontUsually associated with a cold front

Warm frontWarm front

• Leading edge of a warm air massLeading edge of a warm air mass• Angled edge because warm air is Angled edge because warm air is

sliding up and over the cold airsliding up and over the cold air• Slower than a cold frontSlower than a cold front

What weather is associated with a What weather is associated with a warm frontwarm front??

As warm air moves over a colder air mass, As warm air moves over a colder air mass, the air cools. This causes moisture in the the air cools. This causes moisture in the air to condense creating rainy weather. air to condense creating rainy weather. Hot, humid weather usually follows.Hot, humid weather usually follows.

Warm frontWarm front

Behind frontBehind front• Warm airWarm air• ClearsClears• Pressure levels offPressure levels off

Warm frontWarm front

At FrontAt Front• Stratus cloudsStratus clouds• Pressure dropsPressure drops• Long, steady rainLong, steady rain

Warm frontWarm front

Ahead of the frontAhead of the front• Clouds thicken/may rainClouds thicken/may rain• Cold, dry air further awayCold, dry air further away

Stationary frontStationary front

• Occurs when cold and warm air come Occurs when cold and warm air come togethertogether– The system stalls and it rainsThe system stalls and it rains

http://library.thinkquest.org/C0125863/weather/image/front_stationary_en.gif

Occluded frontOccluded front

• Occurs when a cold front catches up Occurs when a cold front catches up to a warm frontto a warm front– rainsrains

How can you find the position of How can you find the position of weather fronts on a weather map?weather fronts on a weather map?

• Always radiate from the center of a Always radiate from the center of a low pressure systemlow pressure system

• Fronts are located between station Fronts are located between station models that are close to each other, models that are close to each other, but have very different weather but have very different weather conditionsconditions

http://ww2010.atmos.uiuc.edu/guides/mtr/af/frnts/wfrnt/gifs/cyc2.gif

General Circulation of Air in the General Circulation of Air in the TroposphereTroposphere

TroposphereTroposphere– Lowest level of atmosphereLowest level of atmosphere– Contains weatherContains weather

The movement of weatherThe movement of weather

• In U. S. caused by prevailing In U. S. caused by prevailing westerlieswesterlies

• Moves weather from (S) West to (N) Moves weather from (S) West to (N) EastEast

• 400 to 600 miles per day400 to 600 miles per day

Jet StreamJet Stream

• At top of the At top of the tropospheretroposphere– Band of Band of fast moving airfast moving air– Directs (controls movement of) air Directs (controls movement of) air

massesmasses

http://ww2010.atmos.uiuc.edu/guides/maps/upa/gifs/jet1.gif

What will temperatures be like in Rochester, when the Jet Stream is to the South of New York?

What will temperatures be like in Rochester, when the Jet Stream is to the North of New York?

Canada USAPola

r Fr

on

tcP mT

Jet Stream/Polar FrontJet Stream/Polar FrontA Side ViewA Side View

StormsStorms

• Low pressure systemsLow pressure systems

HurricaneHurricane

• Form over warm water near equatorForm over warm water near equator• Covers hundreds of square milesCovers hundreds of square miles

– Lasts for daysLasts for days– Common from late summer to early fallCommon from late summer to early fall

• 74-200 mph winds, damaging storm 74-200 mph winds, damaging storm surgesurge

http://www.agu.org/report/hurricanes/Katrina_big.jpg

TornadoTornado

• Form over land at mid latitudes in Form over land at mid latitudes in springspring

• Covers yards and lasts for minutesCovers yards and lasts for minutes• Produces greatest wind speeds on Produces greatest wind speeds on

EarthEarth

http://www.tornadoexpress.com/images/pics/tornado_alley.jpg

Emergency preparednessEmergency preparedness

• Power for light (batteries/generators)Power for light (batteries/generators)• RadioRadio• Warm clothesWarm clothes• Clean waterClean water• First Aid KitFirst Aid Kit

Emergency preparednessEmergency preparedness

Technology and satellites have Technology and satellites have improved forecasting accuracy and improved forecasting accuracy and helps reduce loss of lifehelps reduce loss of life

On shore/Sea BreezeOn shore/Sea Breeze

• DaytimeDaytime• Blows from water toward landBlows from water toward land• Land has lower air pressure and Land has lower air pressure and

higher temperature than waterhigher temperature than water

Off shore/ Land BreezeOff shore/ Land Breeze

• NighttimeNighttime• Blows from land to waterBlows from land to water• Water has lower air pressure and Water has lower air pressure and

higher temperature than landhigher temperature than land