The Trend Technique

• If a phenomenon is in steady state, or is moving at constant speed, the trend technique can be used.
• rate x time = distance
• so if distance traverse by cold front is known over a given time period, its position can be extrapolated in time.
• more accurate on shorter time scales (minutes to hours)
• a short term forecast is called a "nowcast"

QUESTION FOR THOUGHT:

Suppose that is is presently warm and raining. A cold front will pass your area in three hours. Behind the front it is cold and snowing. Make a persistence forecast for your area 6 hours from now. Would you expect this forecast to be correct? Explain. Now, make a forecast for your area using the steady-state, or trend method.