1. Surface Weather Observations
(Worldwide, every 3 Hours GMT starting at 00:00)
Current and past state of the weather e.g. Rain, Fog, etc.
Air temperature
Dry bulb temperature
(Wet bulb temperature)
Maximum, minimum temperatures

2. Surface Observations (continued)
Relative humidity Amount and type of clouds Wind speed and direction Pressure, pressure tendency Precipitation

3. Clouds Aid in weather forecasting Trace atmospheric motions
(e.g. satellite imagery)
Produce precipitation
Reflect sunlight away from Earth
Absorb/emit heat radiation
Absorb or rainout air pollution

5. Basic types of clouds
High
Mid-level
Low

6. “Nimbo-” or
“-nimbus”
means cloud is producing precipitation.
e.g. Cumulonimbus, Cb (thunderstorm)
Nimbostratus, Ns (rain or snow)

8. Cirrus (Ci) clouds over
the Golden Gate bridge
Ci clouds over Germany

9. Altocumulus clouds over Edmundton, Alberta

10. Nimbostratus (Ns) cloud over Germany

11. Cumulus clouds in Victoria, Australia

12. Cumulonimbus (Cb) cloud near Hong Kong

13. Supercell thunderstorm in Australia

14. Clouds over Tucson

15. Wind Vane or Weather Vane
Measures direction wind is blowing FROM

16. “Dove of Peace” by Joseph Rakestraw (1787)

17. Windmill anemometer measures wind speed and direction

22. Water barometers
Berti (1639) in Rome Guericke (c1654) in Magdeburg

23. To make a mercury barometer, just fill a sealed tube with mercury then invert the tube in a container of mercury.

24. Mercury barometer

28. Tanker steam cleaned and closed, crushed when cooled off
Empty bottle
Opened at 2000m
Crushed at sea level

29. Force (air pressure x area)
UP is greater than weight of water DOWN

31. Weather glass or Thunder glass
Used to measure CHANGES
in atmospheric pressure (or temperature)
"decreasing pressure predicts
stormy weather"

32. Hurricane Wilma October 19, 2005 p = 882 mb

36. Location of the station on the map.
The name of the location or airport abbreviation might be given nearby.

37. Air temperature in degrees Fahrenheit (°F)

38. Dew Point temperature in degrees Fahrenheit (°F)
dewpt

39. A staff is rotated around the station.
Wind direction
A staff is rotated around the station.
Temp
dewpt
Remember, winds are identified as the direction FROM which they come. This would be a west northwest wind or about 290º.

40. Attached to the staff are symbols for speed.
Wind Speed
Attached to the staff are symbols for speed.
Temp
dewpt

41. The coding for the wind speed symbols can be generalized as:
half barb about 5 knots
note, barb is on the back end of a wind direction arrow
full barb about 10 knots
these are additive for the total amounts
three full barbs = 30 knots
full flag = 50 knots
65 knots

42. Each pennant (filled triangle) = 50 knots[
Wind Speeds
Each 1/2 flag knots =
5 knots
Each full flag = 10 knots
Each pennant (filled triangle) = 50 knots[

43. Current Barometric Pressure
Temp
dewpt
pressure

44. Barometric Pressure is VERY important!
average barometric pressure at sea level is mb.
current barometric pressure is reported to the nearest TENTH
BUT, in order to save space

45. average barometric pressure at sea level is 1013.25 mb, but
actual barometric pressure varies around this value
+ about 30 mb = 1043 mb
somewhat higher
1013.3
somewhat lower
- about 30 mb = 983 mb

46. So they do not PLOT the beginning number or numbers
1013.3 x
133
they, also, do not PLOT the decimal point, but report to the nearest TENTH

47. Which would make the value most realistic?
From the three numbers, you must INTERPRET whether the preceding value is 10 or 9
Which would make the value most realistic?

48. and then consider whether a 10 or a 9
Add the decimal point
and then consider whether a 10 or a 9
makes the value NEAREST to an average pressure of mb

49. (1013.3 mb) What is the pressure? 084 08.4 1008.4 962 96.2 996.2 281
28.1
1028.1
987.5
875
87.5
322
32.2
1032.2

50. So, more information may be given and must be coded.
Not only is the pressure itself important, but also the way the pressure has been changing.
So, more information may be given and must be coded.

51. How has the barometer been changing?
Temp
dewpt
pressure
trend
+ it is higher now than in the past
- it is lower now than in the past

52. How much the pressure has changed
Temp
dewpt
pressure
trend
change
the amount of change in the past three hours
again, reported in TENTHS without the decimal

53. What has the pressure been doing? Shown diagrammatically
Temp
dewpt
pressure
trend
change
shown

54. graphic depiction of percentage of the sky covered by clouds
Total amount of cloud
Temp
dewpt
pressure
trend
change
shown
graphic depiction of percentage of the sky covered by clouds

55. about 60% no clouds about 10% about 75% about 25% about 80%
Amount
about 60%
no clouds
about 10%
about 75%
about 25%
about 80%
completely overcast
about 40%
sky obscured
about 50%

56. Symbol positions to identify the cloud types
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
Cloud types tell much about the weather conditions. The cloud types are identified by symbols, and classed as low, middle, and high clouds.

57. How much of the sky is covered by low and middle cloud cover?
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
low or middle cloud cover
What amount, in tenths, of the sky is covered by low or middle clouds. This is a coded number with the percentage close to the printed number.

58. What is the present weather?
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
low or middle cloud cover
The current weather is very important.
A detailed set of symbols provides weather descriptions.

59. Symbols for present weather

60. , * . Samples of present weather symbols. rain fog snow haze
slight rain showers ,
thunderstorm
drizzle .
ice or snow pellets
lightning
cloud development not observed

61. Combining symbols tells more of the detail.
intermittent rain, slight at time of observation
continuous rain, slight at time of observation
continuous rain, moderate at time of observation
intermittent rain, moderate at time of observation
intermittent rain, heavy at time of observation
continuous rain, heavy at time of observation

62. 100 different symbols provide details about the PRESENT WEATHER.
(see Class Handout and

63. The visibility is especially important for pilots.
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
visibility
low or middle cloud cover
Visibility is given in miles and fractions

64. The past weather uses symbols.
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
visibility
low or middle cloud cover
PAST , *

65. Past
Weather
Symbols

66. Time precipitation began or ended
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
visibility
low or middle cloud cover
PAST
when
Coded for how many hours ago the precipitation began or ended. Again, the code is close to the number of hours.

67. Height of cloud base PAST
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
visibility
low or middle cloud cover
PAST
when
base
Coded height of base of clouds. Important for pilots.

68. The amount of precipitation
Temp
dewpt
pressure
trend
change
shown
low clouds
middle clouds
high clouds
wxnow
visibility
low or middle cloud cover
PAST
when
base
amount
Amount of precipitation is plotted in inches to the nearest hundredth of an inch.

70. Decode this station.
237 ,, 75 - 1 12 65 6 3

71. any low clouds. any middle clouds. any high clouds
any low clouds? any middle clouds? any high clouds? amount of low and middle clouds height of cloud base visibility barometric pressure trend in pressure pressure three hours ago how has pressure changed present weather past weather when precipitation began/ended amount of precipitation
yes
yes
237 ,, 75
yes - 1 12 6 4 65 6 3
1 mile mb
falling
1024.9
down then steady
temperature dew point wind direction wind speed amount of sky cover
75 °F
continuous slight drizzle
65 °F
rain
south 4
25 knots
.36”
80%