Answers: Finding wind data

By Jack Williams ©2014

Q: What is your favorite source for near real time surface wind visualizations in the mid Atlantic region. I need the information for balloon flight planning in the field.

Curt, Falls Church, Va.

A:  I’ve yet to find any really good visualizations for surface winds because none show the winds in any real detail. That said,  best that I’ve found are NWS surface charts, such as the one this link takes you to. It shows basic weather observations, including wind speeds and directions for the middle Atlantic states. Similar charts are available for other regions.

Let’s first look at the available visualizations and then I’ll describe some sources for text data, which I think might work better for you.

The image below shows part of the chart, which has weather station observations collected shortly before 2 p.m. ET, on Dec. 26.  An NWS Web page explains the symbols used on surface charts–only some of them are used on the chart shown below. In brief, you can imagine the line showing the wind as an arrow that’s flying with the wind and has hit the dot representing the station.

By the way, all of the charts and text products that I refer to use UTC (also known as Zulu) time. When the U.S. is on standard time UTC is five hours later. When we’re on daylight time UTC is four hours later than EDT.

This chart is the best visual way to find wind data because it is relatively uncluttered–for a weather chart. Most such charts show much more information such as lines of equal air pressure, fronts, and centers of high and low air pressure.

Part of a surface chart showing wind speeds and directions reported by weather stations - NWS imagehigh and low air pressure.

The map linked to above and shown in part on the left is from the American Meteorological Society’s DataStreme Web site for students and teachers. Teachers can use such maps to teach students how to draw the more complex maps.

The NWS updates these charts each three hours.

While these charts might work for you, I think that text data might work better. Instead of visualizing data from a relatively small number of weather stations, the text data are updated each few minutes from scores of automated weather stations in any region, unlike the chart data from a relatively few weather stations.

An easy way to access these reports is to go to an NWS Web page with links to Automated Surface Observations Stations (ASOS) in all 50 U.S. states. Once on this page you should use the pull-down menu on the left side of the page to select a state and then the pull-down menu that takes you to the location in that state you want.

This gives you an ordinary English list weather data, not the reports in METAR code you’ll get if  via the “Enter Station ID” box below the pull-down menu.

Since weather conditions change,  you might sometimes want a winds forecast in addition to the latest reported wind speed and direction. Aviation forecasts supply the kind of detail you would want. To find these, you can go to the NWS Web page for Terminal Aerodrome Forecasts (TAFs).

On the right side of this page you’ll see a space to enter the four-letter identifier for the airport you are interested in. For much of the U.S. the four-letter identifier is the same as the familiar three-letter identifier with a “K” added at the beginning, i.e, IAD is KIAD for Dulles International Airport. Unless you are familiar with the METAR code, you should click the “translated” dot next to the identifier box.

To find the four-letter identifier for an airport or other weather station, go to the NWS station information Web page and select the state you’re interested in from the pull-down menu under the “Display All Stations in a State” headline.

Finally, since you are launching balloons, you probably also want information on the winds aloft. Finding useful information on these winds, both observed and forecast, is more difficult. Charts intended for pilots that show winds aloft begin at  3,000 feet altitude, which I suspect is higher than the altitudes you are interested in.

Both observed and forecast wind information for altitudes up to 3,000 feet are available, but it’s intended for meteorologists, pilots, and other users who know a fair amount about meteorology.

The best  source that I’ve found is a NOAA Web page that enables you to plot soundings from the NWS Rapid Update Cycle (RUC) computer forecasting model. A meteorological “sounding” refers to measures of air pressure, temperature, humidity, and wind speed and direction at various altitudes in the atmosphere at a particular location.

On the RUC sounding Web page, you first select a data source–I don’t think it makes any difference for you which one you select because you probably won’t be interested in forecasts for more than a few hours ahead. You then enter either a latitude and longitude or a four-letter airport identifier, and click “Plot sounding.”

Sample of upper-air sounding table. NWS image

When the plot comes up you’ll see a Skew T, Log P diagram, but don’t worry about it; you want to scroll down past the diagram to a table like the one on the left here, which will be on the left side of the soundings page below the diagram. This sample shows only the lower part of the table you’ll see.

The first column is the pressure altitude, which will be very close to the true altitude. The next column is the atmospheric pressure at that altitude in millibars. Don’t worry about the “A” in the next column. The next two columns are the wind direction in degrees from true north and the speed in knots at each altitude.

On the soundings page, between the diagram and the table, you’ll see places to click to see the forecast soundings for one, two, or three hours ahead.

By the way, if you want to learn more about the Skew T, Log P diagram you can go to my answer to a question by a pilot on using such diagrams.

Finally, chapters 6 and 7 of my AMS Weather Book: The Ultimate Guide to America’s Weather, cover weather observations and forecasts, will help you better understand observations and forecasts.

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