Station Model

• TT - Temperature: In the United States surface temperature is expressed in units of degrees Fahrenheit. In most other countries of the world it is expressed in degrees Celsius.
• T_dT_d - Dew point temperature: Expressed in the same units as temperature .
• N - Cloud cover: Total cloud amount represents the fraction of sky covered by cloud.
• VV - Visibility: How far we can see, expressed in units of miles.
• dd - Wind direction: The line drawn represents the direction from which the wind is blowing.
• ff - Wind speed: The barbs on the lines representing wind direction give us information on the wind speed. Wind speed is measured in knots (1 knot =1.15 miles per hour). One long barb equals 10 knots, a short barb 5 knots and a triangle represents a wind speed of 50 knots.
• ww - present weather conditions: Symbols are used to convey information on the type of weather that was observed when the observations were made. The next page of this lesson and your book  list some of these symbols. A more extensive list does exist.
• PPP - Surface Pressure adjusted to sea level. The units are coded in mb.  The leading 9 or 10 are dropped as is the decimal.  So 234 represents a pressure of 1023.4 mb while 834 represents a pressure of 983.4 mb.
• pp - Change in surface pressure over the last three hours. The change in pressure is represented by a value and a line that tells us how the pressure was changing.