Gary Archibald, Weathercaster

I have been asked many times over the years: how do you show the maps on TV? How’s that orchestrated exactly? Are you reading from a prompter or is it ad lib?

Well the time is now to answer these important questions.

SLIDESHOW: How We Weathercast

First and foremost, it’s not really that complex in terms of the setup. Usually, the weathercaster and/or meteorologist stands in front of what is technically called a CHROMA KEY (“green screen”). It is exactly what it appears to be. Some studios have a specially designed “backdrop” hung – it’s green as you can see in the photos I have posted here, hence the name – “green screen”.

Here are some of the essential technical information you need to know:

A chroma key is the removal of a color (or small color range) from one image to reveal another image 'behind' it. The removed color becomes transparent. This technique is also referred to as "color keying", "color-separation overlay" ("CSO") (primarily by the BBC), "greenscreen" and "bluescreen". It is commonly used for weather forecast broadcasts, wherein the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background.

The principal subject is photographed/filmed against a background having a single color or a relatively narrow range of colors, usually in the blue or green because these colors are considered to be the furthest away from skin tone. When the phase of the chroma signal corresponds to the preprogrammed state or states associated with the desired color(s), the signal of the alternate background is composited and presented as the output. When the phase of the chroma signal deviates from the chosen color, the principal video is presented at the output. This process is commonly known as "keying", "keying out" or simply a "key".

A chroma key subject must not wear clothing similar in color to the chroma key color(s) (unless intentional), because the clothing may be replaced with the background video. An example of intentional use of this is when an actor wears a blue covering over a part of their body to make it invisible in the final shot.

Monitors and teleprompters help us tell the story

OK. Now, what about telling the story of weather while standing essentially in front of a green wall. Well, there are monitors to help guide the on-air presenter as she/he broadcasts the segment. On either side of the set – off screen, one is able to position himself/herself in such a way to point out key points on maps, graphs, live shot etc… It does indeed take a lot of pratice to get really good at it for most people. It’s not a natural act.

And while we are up there – we are ad libbing 98% of what we are saying (although at the desk when we are presenting weather news items with video, one-on-one reporter stories it’s a mix of teleprompter and ad-libbing at work. We use a hand-held remote to advance the maps/graphics and we are directed via audio cues (that’s the earpiece that you see on-air which is plugged into a wireless pack that we have attached to our waist by a clip.

We are also of course “miked-up”, so that you can hear what we are saying about the thunderstorms in Florida or the wet weather over Portland OR…or the tornado watch over eastern Nebraska. Always check your batteries. I get paranoid about losing power on-air. That’s disasterous. It’s happened a few times in the past. I changed them regularly! You get the idea. We also stand on a mark – it’s a green line – green duct tape to be exact. Our set is lit precisely so we have to present in front of “the wall” on that line without straying off it – otherwise we will either be to light (washed out – over-exposed) or too dark on camera (with horribly unflattering shadows).

Before we go on air we are forecasting, studying the weather - computer models, text, statistical, visual, radar, and data souces as it pertains to the weather. So, we have to know the story and then we use the visually presentation to assist in the storytelling process. The STORY is and will always be the STAR, the FOCUS. We, as on-air presenters are merely conduits who aid in getting the essential information to you the viewer in (hopefully) an infromed, accurate, enlightening, and authoratative manner. In addition, we would like to entertain, as a bonus.

I hope that this blog helps to answer those questions! Love to hear from you if you have any questions concerning the weather and how we do what we love here at NBC Weather Plus. Take care -

Cheers!