What information does a wind barb show?
Quick answer
On the National Weather Service station plots covered here, the shaft points toward the direction the wind is coming from. The marks on the shaft show speed: a long barb is 10 knots, a short barb is 5 knots, and a pennant is 50 knots. Add the marks to read speed. Plotted speeds are rounded to the nearest 5 knots, so treat the result as a plotted value, not an exact measurement. [S1]
The question, the details, the next step.
I see a line with little marks on a weather map. What information does a wind barb show, and which part should I look at first?
A wind barb shows two things: the direction the wind is coming from and its plotted speed. For the National Weather Service station-plot convention described here, start with the shaft, the main line. It points toward the direction the wind is coming from—not toward where the wind is blowing. Then read the marks attached to the shaft to work out speed. [S1]
For example, if the shaft extends toward the northwest on a plot with compass directions, the wind is from the northwest. It is not a map arrow indicating motion toward the northwest. Check the map’s orientation or compass labels before naming a direction, since the barb itself does not supply a compass rose.
How do I tell the long and short marks apart, and what does the triangle-shaped flag mean?
The marks encode speed in knots. In this NWS convention, one long barb represents 10 knots, one short barb represents 5 knots, and a pennant—the filled, flag-like triangle—represents 50 knots. Add the values of all the marks on the shaft. [S1]
A quick visual key:
- Pennant (flag): 50 knots.
- Long barb: 10 knots.
- Short barb: 5 knots.
- Shaft: indicates the direction the wind is coming from.
Count the flags and barbs attached to the same shaft. Don’t mistake a pennant for a long barb: they represent different amounts. This key applies to the station plots covered by the cited NWS page; another chart or plotting system may use a different convention.
Can you show a worked reading, including how to add the symbols?
Suppose a station plot shows one pennant, one long barb, and one short barb. The speed calculation is:
50 + 10 + 5 = 65 knots
So the plotted speed is 65 knots. If the shaft points toward the northwest, the wind is from the northwest at 65 knots, under this station-plot convention. [S1]
The NWS page says plotted speeds are rounded to the nearest 5 knots and that higher speeds can combine pennants with additional barbs. The symbols therefore give a plotted, rounded speed; this reading alone does not establish the wind’s exact instantaneous speed. [S1]
What’s a reliable way to read one when the symbol is crowded or I’m unsure of the direction?
Separate the two questions rather than trying to interpret the whole symbol at once. First trace the shaft back to the station and compare its orientation with the map’s compass directions: the shaft points toward the direction the wind is coming from. Then count the pennants, long barbs, and short barbs, adding 50, 10, and 5 knots respectively for each. [S1]
If the marks overlap or are too small to distinguish, avoid guessing the speed. Zoom in or consult a clearer version of the chart. Also verify that the map uses the NWS station-plot convention described here; the source establishes this convention for those station plots, not for every weather graphic or symbol system.
A practical checklist
Confirm the chart uses the NWS station-plot convention described here.
Use the map’s compass labels to orient the shaft.
Read the shaft as the direction the wind is coming from.
Count each pennant as 50 knots, each long barb as 10, and each short barb as 5.
Add the marks and remember the plotted speed is rounded to the nearest 5 knots.
A few more useful answers
Does the shaft point where the wind is blowing toward?
No. In the NWS station-plot convention covered here, it points toward the direction the wind is coming from. [S1]
How many knots does a pennant represent?
A pennant represents 50 knots in this convention. Add it to any other marks on the shaft. [S1]
Is a wind-barb speed an exact measurement?
The cited NWS page says plotted speeds are rounded to the nearest 5 knots. The symbol therefore gives a rounded plotted value, not an exact instantaneous speed. [S1]
Sources
References used for this guide.
- [S1] National Weather Service: Wind Barb Information weather.gov · Checked