Each chart has associated with it an intended audience and purpose (some not specifically for the WWW). Quite often, separate charts for different weather elements such as temperature are provided - a surface chart not intended as a thorough depiction of weather conditions. Many common elements exist though, no matter which type of depiction is used. These include air masses - broad areas of quasi-homogeneous weather conditions - and their movement (thus winds), temperatures, and areas of storms. I think the way these charts differ is not so much what they portray, but the interpretation which is required. Some people like seeing the big red L's and blue H's, fierce blue cold fronts with sharp teeth, and gentle red warm fronts with rounded teeth; and others can recognize a baroclinic zone seeing nothing other than plotted data Speaking of which, let's look at how 'surface' data is plotted.

Somewhere, the origin of almost any weather map is a map with plotted data (main site). Maps (usually for larger areas) using such plots are called synoptic charts. Among meanings of the word synoptic are a synopsis and/or account from the same view. Weather observations are routinely made at hundreds of U.S. and many other locations - hourly or more frequently during rapidly changing weather. The observation and dissemination process is a story of its own, the Federal Meteorology Handbook #1 (FMH-1) being a useful references for standards used. The primary means of communicating these observations are SYNOP reports and METAR reports. A close inspection of the format of these codes and information contained is quite helpful, if not memorization if you envision using these frequently. Reading SYNOP reports is very difficult, but reading basic METAR reports is not so difficult, and these (example (main site)) are a significantly better description of weather conditions than typical reports (example). Using these reports most effectively is a story of its own also - I mention these now so the source for the 'surface' data on the plotted charts is clear.

Why do I place the word surface in single quotes, you may ask ? I do so because the data described is not really surface data, but near-surface data; and weather maps often illustrate weather well above the surface. Frankly, the weather which concerns me most is around 5 feet above ground - the cold wind on my face, etc.; and that's precisely where most standard temperature measurements are; though wind is typically measured higher - about 3 - 10 meters (10 - 33 feet).

Below is the standard form for surface data plots and 2 examples. If you are unfamiliar with this, it'll be more clear after reading below.

Both plots contain abundant weather information for one place and time, so a map of these can contain abundant information for many places @ one time - a synoptic chart ! The standard form is designed for SYNOP reports, each of the codes shown corresponding with part of the SYNOP format. The coded data is not plotted as is, but done so such that a plot is more meaningful - the code is used for data transmission. Thus, temperature and dewpoint are shown as whole degrees (usually Fahrenheit in U.S., but Celsius (stupid units) elsewhere), visibility as miles, and accumulated precipitation as inches, among others. Descriptive symbols were developed for past and present weather characteristics (weather symbols), cloud types, and pressure tendencies (click on image to right for descriptions and/or downloading individual symbols) and winds - indicating direction wind blows from and speed. Plotting winds is quite simple - a flag is 50 kt (or 25 m/sec for metric), a long stem is 10 kt (or 5 m/sec), and a short stem 5 kt (or 2½ m/sec), as illustrated :

Very seldom will all of this be plotted. Though the NWS fax surface charts contain station plots using the standard form, most relevant variables are generally reported or plotted. Typically these are present weather, sky cover, temperature and dewpoint, wind, and pressure. Wind barbs are very common, though sometimes I like plotting only the shaft and printing the speed at its end (quite useful when specifically forecasting winds). Thus, I show a couple practical station plots (above & right). These are the forms on most of my plotted charts. Note that several variables are not plotted. This is mainly because METAR reports are the most common source of data. This presents no problem - the form of the plot need not be changed. I show variables most useful for a typical situation, though which variables are plotted depend what your purposes are. Note the symbols below the station circle. Though Canadian surface reports include cloud type (and are typical reported exactly @ the hour), U.S. ones don't (and are most often reported 15 - 5 minutes before the hour). Each include cloud base height and cumulative coverage (from ground up) for each cloud layer though :

When you're out & about, the primary aspect of clouds you probably notice is ceiling. As the name suggests, this is the lowest opaque broken or overcast layer. If a daytime ceiling is low, chances are the sky is drab; if high or non-existent, skies are likely bright. This is significant for many other reasons - abundant solar heating with high or non-existent ceiling, and many aviation concerns, for example. Cloud ceiling is shown on a weather depiction (requires TIF viewer). Though intended for aviation, weather depictions are excellent supplements for satellite images, on which cloud base heights can seldom be estimated well. One thing I hope I'm making clear is reasons why reports of current weather at many sites can be misleading. How many times did you see a report of mostly cloudy or overcast skies, then go outside to a bright, sunny sky covered with transparent cirriform clouds ? I plot ceiling unless it is too high for much significance, then I plot the lowest cloud layer as illustrated - a scattered layer at 2200 feet - or perhaps both. It's my map - I'd make the rules if they existed - though a couple good characteristics of any station plot are clarity and compactness.

Am I suggesting downloading METAR reports and plotting stations on a map every hour like a fool ? Well, I did that many times before PC's were common (actually every 2 or 3 hours was doing well - and base charts are obviously needed), and still sometimes do for special situations; though unless you write a plotting program, chances are you won't get exactly the type of plot you want quickly. Evidently, being a computer geek is part of being an effective modern-age meteorologist...speaking of which, let's see what choices you have then

Among many other fine features, Digital Atmosphere can be used for making rather customized surface plots from downloaded METAR reports. You can choose most variables and regions you wish on color maps including topography; and can even let the program do some analysis. Downloading the reports requires time though - you can sometimes get a detailed current plotted chart slightly quicker at one of the several sites which provide these (examples shown) :