LESSON 6-7: Managing Weather Risk 

This tutorial describes:
• How to include weather events in your project using the risk register
• Weather events as working time uncertainty during defined weather periods 
• Weather Detail window
• How to enter an estimate of non-working days
• How to use non-working time estimates to calculate durations and dates

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1. Include weather events in your project using the risk register.
Weather is a risk whether you are planning a picnic or a project. Use the risk register to include weather events in your project schedule. In the risk register, create a risk. In the Type field, select weather.

2. Weather events as working time uncertainty during defined weather periods.
Note that impact thresholds are removed from the risk register when the weather risk type is selected. This is because weather events are modeled as working time uncertainty during defined weather periods. So rather than selecting Cost and Schedule Impacts for the risk, you will estimate the probability of days when work cannot be done on affected activities.

3. Weather Detail window.
When the weather risk type is selected, the weather detail window becomes active. Click Add to define a weather period for the risk. Type a name for the weather period. Select a period start and period finish date.

4. Estimate of non-working days.
Next, enter an estimate of non-working days for the period. Enter them as a uniform or triangle distribution, for example, 15 to 25 days with the most likely number being 22.
You can also enter an estimate of non-working days as a percentage. In the non-working percentage column, enter the probability that any particular day during the period may be a non-working day.

Persistence is a weather modeling concept that defines the probability of a non-working day immediately following another non-working day. Click Add to add another weather period for the risk. Define the period start and finish dates, and enter the non-working percentage and persistence estimates.

When you create a weather risk, the application runs a simulation of 100 iterations using the risks defined periods and non-working time estimates. The results of the simulation are plotted on a probabilistic calendar that displays the non-working probabilities for each day that occurs during the risks defined periods.

5. Use non-working time estimates to calculate durations and dates.
Use the calendar to confirm that your weather data is being estimated as expected. Finally, assign the risk to the activities that it may affect. When you run a risk analysis, non-working time estimates are used to calculate durations and dates of activities to which weather risks are assigned.