1. DoNow
Name 3-5 observations that are made for weather. (Hint: example = wind)

2. Weather Observations

3. Types of Observations
Temperature
Dewpoint
Atmospheric Pressure
Wind Speed and Direction
Cloud Cover
Humidity
Precipitation Types/quantities

4. Observations
Observations are taken by both weather instruments and individuals

5. Temperature and Dewpoint
Both are measured with a thermometer that is shielded from direct sunlight
Hygrothermometer
Temperature around the world is recorded as oC
Scientists use degrees Kelvin
United States uses oF

7. Dewpoint (Td)

8. Dewpoint (Td) Air around us contains water vapor
Warm air can hold more water vapor than cold air
Dewpoint tells us the temperature at which the current amount of water vapor would saturate the cooler air and start to condense (form dew) on an object
What is saturate?

9. Dewpoint (Td)
If we have a little moisture in the air, we have to cool the air more to get it condense
Can you think of when we see dewpoint not related to weather?

10. Dewpoint (Td)
Soda Can
A cold soda can from the fridge meets the warmer air and forms drops.
Drops form on it because it is colder and cools the air coming in contact with it to below the dew point so it cannot hold the water it contains in vapor form.
Water condenses out of the air and forms on the sides of the can. 
Water vapor or water in the form of a gas exists in the atmosphere. If you listen to weather reports, you will hear a number called the dew point. That number is the temperature. When the temperature drops below that number, the water in the atmosphere condenses. It turns to dew. If you have a glass with ice in it, the temperature on the outside of the glass is below the dew point. When water vapor hits that glass, it turns to dew. In your case, it was a can of soda that became covered with dew. If the dew point had been below the temperature of the soda can, you would not have seen any dew form on the can of soda.

11. Atmospheric Pressure
AKA Barometric pressure
Units of pressure:
Hectopascals (hPa)
Millibars (mb)
Inches of mercury (in Hg)
NOTE: not same as pressure in other sciences (chemistry)

12. Atmospheric Pressure
Reported values are adjusted to sea level

13. Wind Speed and Direction
Speed measured in knots:
1 knot = m/s
1 knot = mph
Weak hurricanes have wind speeds of over 65 knots (75 mph!)
Why do we care about wind direction?

14. Wind Speed and Direction
Help predict where a storm is heading (wind patterns)
Most storms move east-west so look at weather to the east to determine if a storm may come
Helpful for sailors because determines roughness of water

15. Clouds
Cloud amounts and height
Cloud type only done by sight

16. Humidity
Amount of water vapor in the air
What is the relationship between humidity and dewpoint?

17. Humidity and Dewpoint
A high relative humidity indicates that dewpoint is closer to the current air temperature
When humidity is 100%, dewpoint is equal to the current air temperature and the air is completely saturated

18. Humidity and Dewpoint

19. Precipitation Types
What is precipitation?

20. Precipitation Types
Definition – any product of the condensation of atmospheric water vapor that falls due to gravity
Name 3 types of precipitation.

22. Precipitation Types
In pairs, write one sentence to describe each type of precipitation

23. Precipitation Types
Rain – drops of liquid that fall from clouds when water vapor condenses
Diameter > 0.5 millimeters
The drops become too heavy to hold so they fall
Drizzle – rain with droplet diameter < 0.5 millimeters

24. Precipitation Types
Hail – forms within thunderstorm clouds when upward air prevents frozen water pellets from falling
They eventually become heavy and fall in large stone-like shapes
Sleet – slush falling from sky
Raindrops that freeze into ice as they fall

25. Precipitation Types
Snow – ice crystals that form due to sublimation
What is sublimation?

26. Precipitation Quantity
Totality of fallen liquid or solid precipitation for a certain time interval
Measured in mm per hour