Wintertime Blues is the name of this quilt. That is what we have in the eastern USA. We are ready for summer, but the forecast looks like more bitter cold and snow. Yikes!
This time I want to talk about other methods of forecasting. Some are easier to do than others. Some of more accurate than others.
This forecast says what it is doing now it will be doing in the future. This would be like what you see in the table below. Boy I wish that were our forecast
|Today||Tomorrow||The day after tomorrow|
This is certainly and easy method, but is only good for very short range forecasts. Weather can change very quickly so I would not put any money bets on a persistence forecast. But it is so easy even my cat could make this kind of forecast!
Guarding the Catnip (or forecasting the weather) Maybe he can do better than the groundhog!
Steady State or Trend
This method is a bit more sophisticated than using persistence and does require knowledge of meteorology.This method assumes that weather systems such as a cold front will continue to move at the speed that have been moving at and in the same direction. This map from ww2010 shows a cold front moving a distance of 800 miles in 24 hours. We would assume that it will continue to move at the speed and in that direction so we know where it will be 24 hours later. Again this is only good for short range forecasts since systems can change speed and direction.
This method relies on a forecaster recognizing the current weather situation as something he/she has seen before. So a weather person would have to have a good knowledge of past weather scenarios. So you would think that a forecaster with lots of years of experience would do better with this method. The only trouble is seeing a similar situation in the past does not mean it will turn out exactly like that this time. In fact you can pretty much guarantee that it will not turn out the same. I guess this method is like a quilter working in a series. Each quilt will not be exactly like the one before. This method is actually better for longer range forecasts where you are just looking for trends.
The weather forecast for this winter made back in the early fall. Looks like it is shaping up to be just like they said it would be.
There are several different computer models that are used to forecast the weather. All of these models are run and then compared. If they forecast a similar outcome then there is pretty good confidence in the forecast. If the models all predict something different then there is a high degree of uncertainly. So it is less clear if you will get snow or freezing rain. Or if you will get 6 inches or 12 inches of snow.
This type of forecast is based on the average weather (climate) of a particular location. For example, July and August are nearly rain free in Los Angeles. It rains only 1 day in 90 in this area in the summer. That is only a 1% chance of rain. So if I made a forecast that it was going to be sunny this year on the 4th of July I would have a chance of 99% of being right. This would not be that easy to make in other locations.
What is the chance that a particular event will happen. This is given a percentage. The higher the % the more likely it will happen. A 90% chance of snow is certainly more likely than a 20% chance.
How do forecasters stack up against persistence and climatological forecasts?
The forecasters using their models and skills do much better early on. After 9 days you may as well just go with the what you would expect on that particular day (the climate). Looks like persistence is the worst method for forecasting.
Thanks for reading. Not sure what the topic will be next Monday.