Weather Resources - Expanded Discussion

1. NWS Surface Analysis Chart

This is the first step in looking at the day’s weather. What I am interested in here is just an overview of where the surface weather is today. The map is has a one-click magnification, so you can look more closely at areas, station symbols and so forth. In the magnified view, it is particularly useful for getting a picture of surface wind directions and temp/dew point spreads.

2. NWS Standard Barotropic Level Fax Charts

My next stop is to obtain a 700 mb analysis of pressure heights and temperatures. This will aid in locating shortwave and longwave troughs and high pressure centers and ridges. For some idiosyncratic reason, the NWS insists on publishing these charts upside down. So I usually open a "print" copy as a PDF, and then flip it around so I can find Florida and Texas...

3. NWS WPC Short Range Forecast

The Weather Prediction Center folks at College Park, MD generate a 24 hour short range forcast discussion that will quickly summarize the national weather trends for the coming day. Part of the reason for reading this as the third stage of my weather briefing is that the text in this forecast will often refer specifically to weather features that I have already noted on surface analysis and/or 700 mb charts. Consequently, this text begins to reinforce the national weather picture that I am developing in my mind.

4. Earthwinds

A really useful site with which to get a big picture look at the upper air situation is Cameron Beccario's  Earthwinds. It is incredibly dynamic; you can rotate the globe around with your mouse and look at the situation from any point on the globe. In the lower left corner, the menu is suppressed under the word "Earth" on it, and the menu opens. If you click on any point on the map, a display will open in the lower left providing a digital readout of whatever parameters you have selected at that particular point; the units can be changed to taste.

I usually look at the winds at 250 mb, which gives me a good picture of the day at cruise altitude, and then look at the total water content (TWC) at the 700 mb level. This gives me a sense of how wet the atmosphere is around 10,000 feet as well as the flow at that level, which can be influential for thunderstorms. Mostly, this information just prepares me for the next several sites.

5. SPC Sounding Analysis Page

Once I have a reasonable national weather picture developed, I start localizing my day's understanding by looking at the latest soundings from the Storm Prediction Center at Norman, OK. Generally, I only look at wherever I may be going that day, although I may check some locations along a longer route as well. I am primarily interested in inversions, CAPE values, lifted index values, relative humidity and wind direction/strength. In particular, the CAPE and LI values will give an indication of thunderstorm potential, the proximity of the RH plot to temperature may indicate cloud tops, and the wind barbs will give me an idea of low-level wind shifts that may influence departure and arrival planning.

6. SPC Mesoanalysis Pages

The SPC Mesoanalysis pages can be configured to provide a huge amount of weather data. I start with the national sector, but regional sectors of the same data can be obtained here. Radar, county warning areas, cities and highways and the like can be selected on the right side of the page. The top menu bar provides all of the weather options. Under the "Thermodynamics" menu header, I look at 3 sets of data.
  • First I pull up the surface based CAPE plot. This shows the convective available potential energy at the surface, which is one of the raw ingredients for thunderstorm initiation.
  • Second, I look at the surface based lifted index, whichshows the basic instability of the atmosphere, with the more negative numbers indicating greater instability.
  • Lastly, I review the K-Index plot. The K-Index is a computed indication of thunderstorm potential, based on lapse rate, amount of moisture and moisture depth.

7. SPC One Day Convective Outlook

This page will provide both graphical plots and very detailed textual discussion of the 24 hour convective outlook. It nicely wraps up the model that I have already constructed in my mind of the convective situation, based on the soundings and mesoscale analysis.

8. NWS Area Forecast Discussions

This is probably one of the most important pages to read before flying. Start by clicking on the state you are interested in; this will take you to a menu of weather data for that particular state. On the right hand side, you will find a menu button titled "Forecast Discussion". Click on this, and you will arrive at a text page. At the top will be a list of content links, each labelled by the weather station it leads to. For example, Dallas-Fort Worth is labelled "AFDFDW". This will finally bring you to the specific forecaster's written discussion of the current forecast.

The content tends to vary depending on the forecast office and, I'm sure, the individual forecaster. However, you will almost always find a detailed discussion of both the short and long range forecasts, along with some justifications for those forecasts. In some cases, an aviation paragraph will be added that specifically discusses the TAF. This can often contain the forecaster's concerns for the next TAF, and even what they have withheld from the current TAF because they cannot yet substantiate their local gut feel on the trends.

9. NWS Enhanced Radar Image Loop

Now that I have looked at all of the background, it is time to see how things are actually developing. I start with the national radar loop. You can click on any location within this map to pull up the local radar.

10. ADDS Infrared Satellite Plots

Having looked at the radar situation, I take a look at the IR satellite image covering the same area. At the top of the image is a temperature/color scale, which will enable you to relate the color to a static air temperature. This will give you a good idea of the cloud tops, based on what you know about the SAT. The basic idea, of course, is that orange cloud tops are warm, blue tops are cold. Of course, no clouds is usually warm, too, since you are looking at the IR temperature of the dirt...

Different regions can be selected here, as well as other option such as visible satellite imagery.


The Aviation Digital Data Service provides a wealth of useful information. I start with the TAFs on this page. In the lower part of the page, below the map, you can input your destinations and obtain the current METAR (if you check the box) and the TAF. You can also obtain both graphical and textual compilations of area TAFs around the particular region. Note also that if you pull up the ADDS METAR page here, you can pull a set of recent METARs, up to 36 hour prior if you wish to study the trends.

12. ADDS Wind Plots

The ADDS Wind plot will display forecast winds at 3000 foot intervals below FL 180 and 6000 foot intervals above. The forecast time can be selected anywhere from 1 hour to 30 hours into the future. Because you can simply trigger the scroll arrows in the altitude field, you can literally step the plot up or down at will, which allows you to build a better picture in your mind of the winds in the vertical dimension as well as the geographic map. The same plot can be converted to a temperature aloft plot, allowing you to evaluate the upper air temperatures and get an idea what the relationship to ISA will be.

Since you have already looked at the upper atmosphere through Earthwinds, this will hopefully not reveal any surprises; rather, it simply confirms the picture you already have.

13. ADDS Turbulence Plots

The ADDS turbulence plot will function exactly the same way as the Winds plot, allowing you to step up or down at 1 hour intervals for 3 hours, and then 3 hour intervals for the next 12 hours. I have found this plot to be uncannily accurate. It allows me to have a good idea where the bumps are likely to be and which direction of altitude change, up, down, or it doesn't matter, will be the most useful. There really is no reason to be caught unawares regarding choppy air; it is almost always forecast right here.

Turbulence PIREPS can be accessed from this page as well...when there are any!

14. ADDS CIP/FIP Plots

The Current Icing Potential (CIP) and the Forecast Icing Potential (FIP) are highly sophisticated algorithms that identify where and when icing is expected, ranging from light icing to Supercooled Large Droplet (SLD) icing. The CIP displays the present time icing potential; the FIP looks forward for 2 hours then at 3-hour intervals fo 18 hours. Different combinations of severity and probability can be pulled up.

From the CIP/FIP plots page, you can also access icing PIREPS and, most importantly, a chart depicting the freezing level.

15. NWS International Flight Folder

This is a very, very useful site for international planning. All of the old B&W significant weather charts are here, as well as international NOTAMs, volcanic activity, and a comprehensive set of pre-specified route forecasts, one of which is probably going to be close to whatever you are flying. It is well worth some time to explore; I used this site and the next one for several years while flying the North Atlantic.

16. NAVCanada

Not to be outdone, the Canadians have a very useful page which is good not only for Canadian weather, but for the North Atlantic as well.