Weather Forecasting Elisabeth (Lis) Cohen. Motivation Foxtrot Comic Strip.
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Transcript of Weather Forecasting Elisabeth (Lis) Cohen. Motivation Foxtrot Comic Strip.
Weather
Forecasting
Elisabeth (Lis) Cohen
Motivation
Foxtrot Comic Strip
What will the weather be tonight?
1 – Cloud and Rain Observations
2 – Pressure Systems
3 – Current Observations
4 – Computer Models
5 – Predict & Verify
Our Forecasting Steps
Why focus on clouds?
• Rain/Snow producers• Heating and Cooling• Indicator of weather• Come in interesting
shapes
Common Cloud Types
Cloud Levels
• High Cumulus– Size of top of thumb
at arms length
• Low Cumulus– Size of fist at arms length
Photo: WBZ-Mos
Cloud Levels
• High Stratus– Sun and Moon easily seen
• Low Stratus– Sun and Moon difficult to see
Sign of moisture high up in the atmosphere.
(Storms possible in 6-24 hours).
Three Cloud LevelsHigh Clouds
Possible marker of afternoon thunderstorm when clouds seen in the morning are growing or are
very tall.
Three Cloud LevelsMiddle Clouds
Cloud LevelsLow Clouds
Can form drizzle like precipitation
Often indicative of thunderstorms and heavy rain.
Cloud LevelsLarge Vertical Development
Cold and Warm Front Clouds
Cold Front Warm Front
Frontal Movement
Cloud Levels
Satellites
• Monitor one area constantly, as it remains stationary with respect to an observer on earth’s surface
Scan from north to south
Click here for:
Satellite loop of the United States
Are the clouds moving in your direction?
When will they reach you?
RadioMicrowavesInfraredVisible UltravioletX RaysGamma Rays
Wavelengths of LightW
avel
engt
h In
crea
ses
Earth Surface
Infrared Energy
Infrared Energy
High CloudHigh Cloud
Low CloudLow Cloud
Cold
Satellite
Infrared Image
Warm
Appears Gray Appears White
High and Low Clouds in Infrared Image
Visible image Infrared image
How RADAR works
USA Today Weather Book Jack Williams
Click here for:
Infrared Satellite loop of the United States
Are the clouds moving in your direction?
When will they reach you?
Click here for the :Radar Map of the United States
Where is the rain moving?Is it getting heavier or lighter?
Look at the scale
Clear During the Day
Cooler Air
Relatively Warmer Air
All Solar Energy Received = Warmer
Low Clouds During the Day
Some Solar Energy Received = Cooler
Clear at Night
Clear at Night
Ground radiatively cools at night and the energy is lost to space. The ground can get very cool on these nights.
Cloudy at Night
Cloudy at Night
The ground radiately cools at night. Some of that radiation is absorbed by the clouds and reradiated in all directions. Some of that radiation reaches the ground and keeps warms the ground. This keeps it warmer at night.
What clouds are outside now? Click on the image to check the clouds in Colorado.
Ingredients for Cloud Formation
1. Condensation Nuclei
2. Moisture
3. Cooling / Lift
Surface Weather Map
General Rules• Low-
– cloudy skies
– Sucks air
– Lousy
• High-– mostly clear
– blows air
– Happy
Click here to see the: United States Surface Weather Map
Where are the highs and the lows?Are their lows close by that might
be associated with clouds?
Winds Moving Air Masses
Warm Air Cold Air
Temperature
During the Day…
Temperatures decrease with height, in this layer of the atmosphere.
At Night….
Air at the ground is often cooler than the
air above it.
Temperature
Winds at Night
Cooler Air
Relatively Warmer Air
Local Observations
• Past and Current
– Wind Speed
– Wind Direction
– Temperature
– Humidity
Click here for: Surface Observations in Denver (Mesowest data)find your city on the map
Click here for:Computer model forecast for United States
Weather 6 hours from now
Climate Normals for Boulder
Helpful Hints
Observation Forecast Reason
NightCooler
than day
Ground Cools (Outgoing Longwave Radiation> Incoming Shortwave
Radiation +Incoming Longwave Radiation)
Clear SkyCool
EveningThe atmosphere is mostly transparent to the outgoing
longwave radiation.
Calm WindsCool
EveningLittle mixing of air from aloft keeps the air close to the
ground cooler.
Low Humidity
Cool Evening
The lack of moisture will mean less heat will be reradiated back to earth.
Your Forecast
Observation Forecast Reason
Clouds-satellite
-sky cover-highs/lows
Temp -clouds-winds
Rain-high/lows
-radar
Other