When viewing the static weather imagery in EZWxBrief, you may notice that the time slider at the bottom starts at the very far left position or very far right position depending on the imagery being viewed. Here's what's going on and why there's a difference.
Given that the time slider is always rendered with time increasing from left to right, any imagery that is solely based in the recent past will start with the slider in the right-most position. This is so that when you visit that imagery collection it will render with the most recent image available in the collection. This includes imagery such as the surface analysis chart below. In this case, the latest (most recent) surface analysis available is valid at 09Z as shown by the yellow arrow. Moving the slider to the left will cause the imagery to move backward in time.
If the imagery collection is a forecast of some sort, then the time slider will start at the left-most position. This includes any forecast such as the prog charts as shown below with the blue arrow. In this case, moving the slider to the right will cause the imagery to move forward in time.
It is important to understand that when the slider is first positioned when you are viewing a forecast collection, you may notice that some of the forecasts might be valid in the recent past. This is very normal behavior. This is because forecast models are run at intervals of one hour, six hours or even 12 hours. Because of this, some of the early forecast hours (including the model's analysis) may have valid times in the past since the new run of the model may not be issued for several more hours. Even so, it's good to see the trends of how the forecast is evolving over time.
Interested in learning more about the Skew-T? You can order your copy of The Skew-T log (p) and Me book today in soft cover or eBook format.
Most pilots are weatherwise, but some are otherwise™
Dr. Scott Dennstaedt
Weather Systems Engineer
CFI & former NWS meteorologist