ADDS Wind/Temp Help

Wind/Temp Plots

The Winds/Temps page provides 2D graphics of winds and temperatures at a multitude of altitudes from the current time until multiple days in the future.

Wind Speed and Streamlines

There are two presentation styles used to convey wind speed and direction. Common to both graphics is the wind speed, which is contoured and color-filled to indicate certain ranges of speed. Very low wind speeds do not receive a color, but progressively faster wind speeds are colored from blue to yellow, orange, gold, then red. Since wind speed generally increases with increasing height, users should expect to see more frequent orange to red colors at high altitudes. During most of the year, users can easily locate the "jet stream" by viewing the chart around 36,000 feet (FL360) and finding the ribbon of fastest-moving air.

The direction of the wind is very obvious on the wind streamlines graphics, which almost give the appearance of rivers or channels of wind (See Fig. 2). This presentation method also makes obvious the locations of high and low pressure centers and upper level ridges and troughs. The alternative presentation style is the classical "wind barbs" that show both wind speed and direction on a single icon that is best explained via the figure shown below.

Wind Barb
Figure 1: Wind Barbs

A sample plot of wind barbs can be seen in Fig. 3.

The computer models that create these data typically have thousands of "pixels" of information, but not every pixel can contain an icon for wind speed and direction, so only a representative sample of pixels are displayed on the graphic.

Wind streamlines
Figure 2: Wind Speed and Streamlines
Wind Speed
Figure 3: Wind Speed with Wind Barbs

Temperature and Temperature Difference

The temperature graphics are relatively easy to understand with a contour line created for every interval of 5 degrees C (See Fig. 4). The horizontal variation of temperature is greatest at low altitudes, especially at the earth's surface and lessens with increasing height. Therefore, do not expect to see much variation of temperature on the plot at FL360 where the temperature regularly hovers around -50 to -55C no matter where in the country you look.

The graphics called temperature difference are rather unique on ADDS. Because temperature can affect aircraft performance, some instruments are calibrated with respect to the ICAO standard atmospheric temperature. If the weather conditions on a given day are drastically different than this reference temperature, as they would be often during the hottest summer days, then pilots need to alter their calculations. For this reason, ADDS display graphics of the departure of upper-level temperature from the ICAO standard along with the standard temperature value at the level shown. Each contour is labelled with "ISA" meaning ICAO standard atmosphere followed by an offset like "+5" meaning 5 degrees C higher (warmer) than standard temperature (See Fig. 5). Most pilots have methods to enter the departure value rather than the actual temperature so this chart should simplify a pilots flight preparations.

In addition, there is one very special graphic depicting the aviation effect of high surface temperatures that lower the air density to dangerously low values and require longer runway lengths before an aircraft may lift off the runway. This is known as density altitude deviation. The graphic for temperature difference at the surface level is designed to give pilots this information. On this graphic, users will find values from zero to 4000 feet indicating the perceived additional altitude of the runway rather than the actual elevation. As an example, let's consider a moderately high altitude airport at Fort Collins-Loveland, Colorado, (KFNL) which is located at 5016 feet above sea level. A typical day in mid-summer may show a value of density altitude deviation of 3000 feet on the graphic. If so, the EFFECTIVE altitude of the airport is then 5016+3000=8016 feet above sea level. Some pilots may find this altitude requires a much longer runway distance to gain sufficient airspeed to achieve the lift needed for takeoff.

Temperature
Figure 3: Temperature
Temperature difference
Figure 4: Temperature Difference from
standard atmosphere

URL Options

Here is a list of the URL options:

  • type={wind|windstrm|temp|isa} - The type of plot:
    • wind - Wind speed with wind barbs
    • windstrm - Wind speed with streamlines
    • temp - Temperature
    • isa - Temperature difference from standard atmosphere
    The default is wind.
  • level={sfc|30|60|90|120|150|180|240|300|360|420|480} - The vertical level in 100s of feet. The default is sfc.
  • fore=### - Specifies the forecast time. Forecast times run hourly to 18 hours and then every 6 hours to 84. The default is 0.


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