VIV: Verification, Initialization and Verification (Photo Credit: National Weather Service. Process Credit: 26 Operational Weather Squadron)
The central U.S. is no stranger to interesting and sometimes unusual weather patterns, but for those who have been watching, this winter has been unusual to say the least. Arkansas and Missouri went from cold and snowy at the beginning of one week, to tornadoes and warm by week’s end. This brings up the question, how have the forecasters in these locations been doing so well? One of the tools that forecasters use is known as VIV or Verification, Initialization and Verification.
First, it is important to note that any sort of weather models are mathematical algorithms. That is not to state that these models do poorly, it’s quite the opposite in that they are getting better as time goes on. They do, however, need to be checked for accuracy of the product, sometimes one model will work better that then others, sometimes none work well. While each forecaster seemingly has their own take and models they prefer, much of this process remains the same.
The first step of this process is Verification. This stage is checking the model against current weather observations. If the forecaster is looking at a 12 hour model run for winds, they are going to check this against the observations for winds in their given area. The model may be disregarded based on what the current weather pattern is, or adjusted. Whether or not the model is thrown out can, honestly, be situational. For instance, forecasters in Europe would have one or more products that would not handle the position of a cut-off low well. The model would handle winds, temperatures, and clouds accurately, but would want to move the pressure system out of the region sooner than expected. In situations like this, an experienced forecaster would adjust the model for the movement out and continue to use it.
The second part of the process is Initialization. This stage is checking the model against the previous model run. This is primarily to make sure there are not any major discrepancies between the two runs. If any are found and the new model is handling the situation well, the new model can be picking up on things the forecaster could have missed.
The final step is, again, Verification, this is continuing to check the model against current weather observations to make sure it’s still accurate. This part of the process runs similar to the first part, wherein the forecaster can check and see if their forecast is still accurate or if it needs to be amended. The only major difference between this step and the first step is that the final Verification is done every hour.
The VIV process is a handy and important process in every forecaster’s tool belt. Done properly and regularly it can help enhance a forecast and insure a more accurate forecast. This process or one of a similar nature is done for every forecast and has only continued to become more prevalent as model forecasting is becoming more of the norm.
To learn more about other high-impact weather events from across North America, be sure to click here!
To learn more about National Weather Service MOS be sure to click here!
©2018 Weather Forecaster Kevin W. Owens