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The National Weather Service (NWS) provides weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy. NWS data and products form a national information database and infrastructure which can be used by other governmental agencies, the private sector, the public, and the global community.
Weather Forecasting - Tracking your Observations and Determining the Big Picture
Chris Strong with the National Weather Service discusses how you can determine the big picture from what's going on in your location.
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Chris Strong: Hi! I am Christ Strong with the National Weather Service and I am talking to you today about how you can forecast the weather.
The next thing we are going to talk about is how you can determine the big picture from what's going on in your location. From the beginnings of time, meteorologists have looked at what's going on at their location to figure out exactly what they are going to say, is going to happen in the future. But in order to know what's going to happen in the future, certainly you have to know not what's just going on where you are but what's going on all around you, what the bigger picture is.
So, if we take our observation and we figure out exactly what our surface pressure was, we can look at what surface pressures are all across the country, all across the globe.
Once we figure out where the highest pressures are and where the lowest pressures are, we can figure out where the centers of big whirlpools of air are in the atmosphere and those big whirlpools are going to tell us a lot.
If we look at the television weather cast on TV, they will usually have a map that has Hs and Ls on it. Well, what are those Hs and Ls mean? They are simply who has the highest pressure and who has the lowest pressure in a region.
If we look at a high pressure area, that's a big whirlpool of air, that's moving around in a clockwise direction. So where it's circulating around this H in a clockwise motion, again drawing northward colder air down to the south and warmer air in the south up to the north.
Low-pressure areas are the same thing. Low pressure is just a whirlpool of air that's circulating air in a counterclockwise direction. It's moving warm air to the north and again, and colder down to the south. But these low-pressure areas are generally areas of storminess and storm systems.
The middle of big winter storms are at low-pressure, the middle of hurricanes are at low-pressure. Storm systems are marked by these low-pressure systems; these low-pressure whirlpools of counterclockwise moving air.
So, if we look at the pressure map of where pressures are all across the country, just knowing one individual pressure point at your location isn't going to tell you too much but if you know what's going on pressure wise across the whole country, we can see where the centers of these great whirlpools of air are in the atmosphere, and from that we can learn a lot.
So, I am just looking at the weatherman's map on television or pulling up a latest surface map. You can see exactly where the centers of these whirlpools are, where the high-pressure and low-pressure are, and how they're moving overtime if you tract them over a period of few days.
Once we have those down, we can also use our satellite imagery and radar imagery. Instead of looking at it at a local scale, we can look at it more broadly and see how rain and clouds match up with these low-pressure systems, these storm systems and exactly how they are moving again.
So, once we start tying everything together, tying together the surface observations not just from our station, but also all across the nation, tying that together with a radar imagery and tying that together with the satellites, we can start to get a broader picture of not - again, what's just going on our spot but what's going on all around us.
And once we start looking at that over a period of hours, over a period of days, we can really see how these storm systems are moving and just by simple extrapolation we can start to get an idea of where things are going to be moving over the next few days.