How we do it

I have been receiving plenty of e-mails regarding forecasting. What tools we use, charts etc... Here is a quick look at how we do it. We utilize different methods in order to reach a forecast consensus. There are many that can be used to create a forecast. The one used depends upon the experience of the forecaster, how reliable it is and how confident he/she feels about the method. Here are a few examples.

Persistence Method : In other words, Today equals Tomorrow
The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 87 degrees today, the persistence method predicts that it will be sunny and 87 degrees tomorrow. If we got 1 inch of rain today, then tomorrow we should get the same. This method is pretty good when patterns don't change . It also works well in places like southern California, where summertime weather conditions vary little from day to day.

Trends Method : Involves Math
This one involves determining the speed and direction of movement for fronts, highs and lows, and areas of clouds and rain. This will give us an idea where any of those features will be in the near future. For example, if a storm system is 1000 miles west of your location and moving to the east at 250 miles per day, using the trends method you would predict it to arrive in our area in 4 days.

Using the trends method, you would predict this weather system to move another 800 miles in the next 24 hours, reaching the East Coast of the United States. The trends method works well when systems continue to move at the same speed in the same direction for a long period of time. If they slow down, speed up, change intensity, or change direction, the trends forecast will probably not work as well.

Analog Method: This one is a bit more difficult, it involves examining today's forecast scenario and remembering a day in the past when the weather scenario looked very similar. The forecaster would predict that the weather in this forecast will behave the same as it did in the past.

Numerical Weather Prediction: Numerical Weather Prediction (NWP) uses the power of computers to make a forecast. Supercomputers run model data on many atmospheric variables such as temperature, pressure, wind, and rainfall. A forecaster examines how the features predicted by the computer will interact to produce the day's weather. This is not a perfect method as some of the data entered could be corrupt. Also if the initial weather conditions are not known, the computer's prediction will not be entirely accurate.
Despite these flaws, the NWP method is probably the best of the ones mentioned above.

Here at the 7weather office we mostly rely on Numerical Weather Prediction and Trend forecasting, although sometimes persistence forecasting works well during winter months. After we review all this data we compare our findings with what the National Weather Service is showing and formulate our daily forecasts accordingly.

But as with everything, there is plenty to learn about Mother Nature and she keeps throwing us curve balls. As soon as we think we have something figured out, she opens the door to another mystery.