The "Climatology" Technique a forecast that is based on "climatology" or average weather example: Lets say the climatological records show that it rains only 1 day out of 100 during the summer months in LA. Then, if you forecast "no rain" for any day in July and August, the probability you will be wrong is 1/100. Therefore, the probability you will be right is about 99% NOTE: precip forecasts are usually given as probabilities ex: "there is a 60% chance of rain today" this means that there is a 60% chance of measurable precip at any random place in the forecast area Accuracy and skill in forecasting What is an accurate forecast? your forecast for tonights min temp is 0°F if the actual min was 1°F, is in inaccurate? if the actual min was 10°F, is in inaccurate? Accuracy (in forecasting) is arbitrary and relative - it's not clearly, objectively defined How does a forecast show skill? must be more accurate than utilizing persistence or climatology persistence is "hard to beat" on a time frame of minutes to hours skill is often shown on time frame of hours to a few days Beyond 10 days, forecasts are generally no better than those generated by climatology QUESTION FOR THOUGHT: Climatology shows that the skies over Vancouver, Canada are cloudy 327 days a year. If you were to forecast cloudy skies for every day of the year, how accurate will your forecasts be? Do your forecasts show skill? Explain.