Weather Forecasting Elisabeth (Lis) Cohen
-
Upload
sebastian-spears -
Category
Documents
-
view
27 -
download
0
description
Transcript of Weather Forecasting Elisabeth (Lis) Cohen
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
Cloud Levels
• High Cumulus– Size of top of thumb
at arms length
• Low Cumulus– Size of fist at arms length
Photo: WBZ-Mos
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
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
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 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
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.
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?
Click here for:Computer model forecast for United States
Weather 6 hours from now
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