Example Surface 3 Hour Temperature and Wind Change
Positive temperature change areas are contoured in solid yellow lines and indicate that the temperature is rising in that region. Negative temperature change areas are contoured in dashed yellow lines and indicate that the temperature is falling in that region. Both temperature change areas are contoured in intervals of 5 degrees Fahrenheit. Therefore, a positive temperature change contour of 5 would indicate that the temperature has risen by 5 degrees Fahrenheit in the past 3 hours within that contour.
The 3 hour wind change is represented by wind vectors in units of meters per second, as indicated by the length of each wind vector. The wind vectors also show the change in wind direction during the past 3 hours, as indicated by the direction the arrow is pointing. The length and magnitude of the strongest wind vector is shown in the lower right-hand corner.
The 3 hour wind change can help show the location of fronts, since one characteristic of both cold and warm fronts is a change in wind direction across the front.
The example image above shows an area of negative temperature change and an increase in the westerly winds located in Iowa. Both of these features are indications that a cold front has passed through the area.