Station 46029 (LLNR 688) - COLUMBIA RIVER BAR - 20NM West of Columbia River Mouth Image indicating link to RSS feed of recent meteorological observations for station 46029


Conditions at 46029 as of
(8:30 am PDT)
1530 GMT on 07/13/2026:
     

Click on the graph icon in the table below to see a time series plot of the last five days of that observation.

5-day plot - Wind Direction Wind Direction (WDIR): N ( 360 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 11.7 kts
5-day plot - Wind Gust Wind Gust (GST): 13.6 kts
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES):30.11 in
5-day plot - Air Temperature Air Temperature (ATMP): 56.5 °F
5-day plot - Water Temperature Water Temperature (WTMP): 56.8 °F
5-day plot - Wind Speed at 10 Meters Wind Speed at 10 meters (WSPD10M): 13.6 kts
5-day plot - Wind Speed at 20 Meters Wind Speed at 20 meters (WSPD20M): 13.6 kts
5-day plot -  Wind Speed, Wind Gust and Atmospheric Pressure Combined plot of Wind Speed, Gust, and Air Pressure
Supplemental Measurements
Lowest 1-minute Pressure
Time (PDT)Pressure
8:30 am30.11 in
Highest 1-minute Wind Speed
Time (PDT)5-day plot - 1-Minute Wind Speed WSPD 5-day plot - 1-Minute Wind Direction WDIR
8:24 am 13.6 kts N ( 350 deg true )
Previous observations
TIME
(PDT)
5-day plot - Wind Direction
WDIR
 
5-day plot - Wind Speed
WSPD
kts
5-day plot - Wind Gust
GST
kts
5-day plot - Wave Height
WVHT
ft
5-day plot - Dominant Wave Period
DPD
sec
5-day plot - Average Wave Period
APD
sec
5-day plot - Mean Wave Direction
MWD
 
5-day plot - Atmospheric Pressure
PRES
in
5-day plot - Pressure Tendency
PTDY
in
5-day plot - Air Temperature
ATMP
°F
5-day plot - Water Temperature
WTMP
°F
5-day plot - Dew Point
DEWP
°F
5-day plot - Salinity
SAL
psu
5-day plot - Visibility
VIS
nmi
5-day plot - Tide (above MLLW)
TIDE
ft
2026-07-13 08:20 am N 11.7 13.6 3.6 74.5 NW30.11- 56.5 56.7----
2026-07-13 08:10 am N 13.6 15.5 3.6-4.5 NW30.11- 56.3 56.7----
2026-07-13 08:00 am N 13.6 15.5----30.11+0.01 56.5 56.7----
2026-07-13 07:50 am N 13.6 15.5 3.6 84.4 NW30.11- 56.5 56.7----
2026-07-13 07:40 am N 13.6 17.5----30.11- 56.5 56.7----
2026-07-13 07:30 am N 13.6 15.5----30.11- 56.5 56.7----
2026-07-13 07:20 am N 13.6 17.5 3.6 84.8WNW30.10- 56.5 56.7----
2026-07-13 07:10 am N 13.6 15.5 3.6-4.8WNW30.10- 56.5 56.7----
2026-07-13 07:00 am N 13.6 15.5----30.10+0.00 56.5 56.7----
2026-07-13 06:50 am N 13.6 15.5 3.6 74.9WNW30.11- 56.3 56.7----
2026-07-13 06:40 am N 13.6 15.5----30.11- 56.3 56.7----
2026-07-13 06:30 am N 13.6 15.5----30.11- 56.3 56.7----
2026-07-13 06:20 am N 13.6 15.5 3.6 84.7WNW30.10- 56.3 56.7----
2026-07-13 06:10 am N 13.6 15.5 3.6-4.7WNW30.10- 56.3 56.7----
2026-07-13 06:00 am N 13.6 15.5----30.10+0.00 56.3 56.7----
2026-07-13 05:50 am N 13.6 15.5 3.6 85.0WNW30.10- 56.3 56.8----
2026-07-13 05:40 am N 13.6 17.5----30.10- 56.3 56.8----
2026-07-13 05:30 am N 13.6 15.5----30.10- 56.3 56.7----
2026-07-13 05:20 am N 11.7 15.5 3.6 85.2WNW30.10- 56.3 56.8----
2026-07-13 05:10 amNNW 11.7 15.5 3.6-5.2WNW30.10- 56.3 56.8----
2026-07-13 05:00 amNNW 11.7 13.6----30.10+0.00 56.3 56.8----
2026-07-13 04:50 amNNW 13.6 15.5 4.3 85.3WNW30.10- 56.3 56.7----
2026-07-13 04:40 amNNW 13.6 15.5 4.3-5.3WNW30.10- 56.3 56.7----
2026-07-13 04:30 amNNW 11.7 13.6----30.10- 56.3 56.7----
2026-07-13 04:20 amNNW 9.7 13.6 3.9 85.1WNW30.11- 56.3 56.7----
2026-07-13 04:10 amNNW 11.7 13.6 3.9-5.1WNW30.11- 56.3 56.7----
2026-07-13 04:00 amNNW 11.7 13.6----30.11+0.00 56.3 56.5----
2026-07-13 03:50 amNNW 11.7 13.6 4.3 85.3WNW30.10- 56.3 56.5----
2026-07-13 03:40 amNNW 11.7 13.6----30.10- 56.3 56.5----
2026-07-13 03:30 amNNW 11.7 13.6----30.10- 56.5 56.5----
2026-07-13 03:20 am N 11.7 13.6 4.3 75.3WNW30.10- 56.5 56.5----
2026-07-13 03:10 am N 11.7 13.6----30.10- 56.5 56.7----
2026-07-13 03:00 am N 11.7 13.6----30.10-0.01 56.5-----
2026-07-13 02:50 am N 11.7 13.6 4.3 85.4WNW30.10- 56.5 56.7----
2026-07-13 02:40 am N 9.7 13.6----30.09- 56.5 56.7----
2026-07-13 02:30 am N 9.7 13.6----30.09- 56.5 56.7----
2026-07-13 02:20 am N 11.7 13.6 4.3 85.6 NW30.09- 56.5 56.7----
2026-07-13 02:10 am N 9.7 13.6 4.3-5.6 NW30.09- 56.5 56.7----
2026-07-13 02:00 am N 9.7 11.7----30.09-0.01 56.5 56.7----
2026-07-13 01:50 am N 9.7 11.7 4.9 85.7WNW30.09- 56.5 56.7----
2026-07-13 01:40 am N 9.7 11.7----30.09- 56.5 56.7----
2026-07-13 01:30 am N 9.7 11.7----30.09- 56.5 56.7----
2026-07-13 01:20 am N 9.7 11.7 4.9 95.7 NW30.10- 56.5 56.7----
2026-07-13 01:10 am N 9.7 13.6----30.10- 56.7 56.7----
2026-07-13 01:00 am N 9.7 11.7----30.10+0.00 56.7 56.7----
2026-07-13 12:50 am N 9.7 11.7 5.2 85.8WNW30.10- 56.7 56.8----
2026-07-13 12:40 am N 9.7 11.7----30.10- 56.7 56.8----
2026-07-13 12:30 am N 11.7 13.6----30.10- 56.7 57.0----
2026-07-13 12:20 am N 9.7 13.6 4.9 85.6WNW30.10- 56.7 56.8----
2026-07-13 12:10 am N 9.7 11.7----30.11- 56.7 56.8----
2026-07-13 12:00 am N 9.7 11.7----30.11+0.01 56.8 56.8----
2026-07-12 11:50 pm N 9.7 11.7 4.6 95.6 NW30.11- 56.8 56.7----
2026-07-12 11:40 pm N 11.7 13.6----30.11- 56.8 56.7----
2026-07-12 11:30 pm N 9.7 11.7----30.11- 56.8 56.5----
2026-07-12 11:20 pm N 9.7 13.6 4.9 85.7WNW30.11- 56.8 56.7----
2026-07-12 11:10 pm N 11.7 13.6 4.9-5.7WNW30.11- 56.8 56.7----
2026-07-12 11:00 pm N 9.7 11.7----30.11+0.00 56.8 56.8----
2026-07-12 10:50 pm N 9.7 13.6 4.9 85.8WNW30.11- 57.0 56.8----
2026-07-12 10:40 pm N 11.7 13.6----30.11- 57.0 56.8----
2026-07-12 10:30 pm N 11.7 13.6----30.11- 57.0 56.8----
2026-07-12 10:20 pm N 11.7 13.6 4.6 95.6 NW30.11- 57.0 57.0----
2026-07-12 10:10 pm N 11.7 13.6 4.6-5.6 NW30.11- 57.0 57.0----
2026-07-12 10:00 pm N 11.7 13.6----30.11-0.01 57.0-----
2026-07-12 09:50 pm N 11.7 15.5 4.6 95.5 NW30.11- 57.0 57.2----
2026-07-12 09:40 pm N 13.6 15.5 4.6-5.5 NW30.11- 57.2 57.2----
2026-07-12 09:30 pm N 13.6 15.5----30.10- 57.2 57.2----
2026-07-12 09:20 pm N 13.6 17.5 4.6 95.3WNW30.10- 57.2 57.4----
2026-07-12 09:10 pm N 15.5 17.5----30.10- 57.2 57.6----
2026-07-12 09:00 pm N 13.6 17.5----30.10-0.02 57.2 57.6----
2026-07-12 08:50 pm N 15.5 17.5 4.6 95.6 NW30.10- 57.4 57.6----
2026-07-12 08:40 pm N 13.6 17.5----30.10- 57.4 57.6----
2026-07-12 08:30 pm N 13.6 15.5----30.10- 57.4 57.6----
2026-07-12 08:20 pm N 13.6 15.5 4.3 95.2WNW30.10- 57.4 57.6----
2026-07-12 08:10 pm N 13.6 15.5 4.3-5.2WNW30.11- 57.6 57.6----
2026-07-12 08:00 pm N 13.6 17.5----30.11-0.02 57.6 57.6----
2026-07-12 07:50 pm N 13.6 17.5 4.3 95.2WNW30.11- 57.6 57.7----
2026-07-12 07:40 pm N 13.6 17.5----30.11- 57.7 57.7----
2026-07-12 07:30 pm N 13.6 17.5----30.11- 57.7 57.9----
2026-07-12 07:20 pm N 13.6 15.5 4.3 95.1WNW30.11- 57.7 57.7----
2026-07-12 07:10 pm N 13.6 15.5 4.3-5.1WNW30.11- 57.7 57.6----
2026-07-12 07:00 pmNNW 13.6 17.5----30.12-0.02 57.7 57.6----
2026-07-12 06:50 pmNNW 15.5 17.5 4.3 95.3WNW30.12- 57.7 57.6----
2026-07-12 06:40 pmNNW 15.5 17.5 4.3-5.3WNW30.11- 57.7 57.6----
2026-07-12 06:30 pmNNW 15.5 19.4----30.11- 57.7 57.7----
2026-07-12 06:20 pmNNW 15.5 17.5 4.6 95.2WNW30.11- 57.7 57.7----
2026-07-12 06:10 pmNNW 15.5 19.4 4.6-5.2WNW30.11- 57.7 57.7----
2026-07-12 06:00 pmNNW 15.5 17.5----30.12-0.04 57.9 57.7----
2026-07-12 05:50 pmNNW 15.5 17.5 4.3 95.2 NW30.12- 57.9 57.7----
2026-07-12 05:40 pmNNW 15.5 19.4----30.12- 57.9 57.9----
2026-07-12 05:30 pmNNW 15.5 17.5----30.13- 57.9-----
2026-07-12 05:20 pmNNW 15.5 17.5 3.9 95.6 NW30.13- 57.9 57.9----
2026-07-12 05:10 pmNNW 15.5 19.4 3.9-5.6 NW30.13- 57.7 57.7----
2026-07-12 05:00 pmNNW 13.6 17.5----30.13-0.03 57.9 57.9----
2026-07-12 04:50 pmNNW 13.6 17.5 3.9 95.4 NW30.13- 57.9 58.1----
2026-07-12 04:40 pmNNW 13.6 17.5 3.9-5.4 NW30.14- 57.9 58.3----
2026-07-12 04:30 pmNNW 15.5 17.5----30.14- 57.9 58.3----
2026-07-12 04:20 pmNNW 15.5 19.4 3.9 95.8 NW30.14- 57.9 58.5----
2026-07-12 04:10 pmNNW 15.5 17.5 3.9-5.8 NW30.14- 57.9 58.5----
2026-07-12 04:00 pmNNW 15.5 17.5----30.14-0.02 57.7 58.6----
2026-07-12 03:50 pmNNW 15.5 17.5 4.3 96.7 NW30.14- 57.9 59.0----
2026-07-12 03:40 pmNNW 13.6 15.5----30.14- 57.9 59.2----
2026-07-12 03:30 pmNNW 13.6 15.5----30.15- 57.9 59.4----
2026-07-12 03:20 pmNNW 11.7 13.6 4.6 97.3WNW30.15- 57.9 59.2----
2026-07-12 03:10 pmNNW 11.7 13.6 4.6-7.3WNW30.15- 57.9 59.2----
2026-07-12 03:00 pmNNW 11.7 13.6----30.16-0.01 57.9 59.2----
2026-07-12 02:50 pmNNW 11.7 13.6 4.3 96.9 NW30.16- 57.9 59.2----
2026-07-12 02:40 pm N 9.7 11.7----30.16- 57.7 58.8----
2026-07-12 02:30 pm N 9.7 11.7----30.16- 57.7 58.6----
2026-07-12 02:20 pm N 9.7 11.7 3.9 96.9WNW30.16- 57.7 58.8----
2026-07-12 02:10 pm N 9.7 11.7 3.9-6.9WNW30.16- 57.7 59.4----
2026-07-12 02:00 pm N 9.7 11.7----30.16+0.00 57.6 59.0----
2026-07-12 01:50 pm N 9.7 11.7 4.3 96.9WNW30.16- 57.6 58.6----
2026-07-12 01:40 pm N 9.7 11.7----30.16- 57.6 58.6----
2026-07-12 01:30 pm N 9.7 11.7----30.16- 57.6 58.3----
2026-07-12 01:20 pm N 9.7 11.7 3.9 96.6 NW30.16- 57.6 59.0----
2026-07-12 01:10 pm N 7.8 9.7 3.9-6.6 NW30.16- 57.4 59.2----
2026-07-12 01:00 pm N 7.8 9.7----30.16-0.02 57.4 58.5----
2026-07-12 12:50 pmNNW 7.8 9.7 4.3 106.5 NW30.16- 57.4 58.6----
2026-07-12 12:40 pmNNW 7.8 9.7 4.3-6.5 NW30.16- 57.4 59.0----
2026-07-12 12:30 pmNNW 7.8 7.8----30.16- 57.4 59.2----
2026-07-12 12:20 pmNNW 7.8 9.7 3.9 86.4WNW30.16- 57.4 59.7----
2026-07-12 12:10 pmNNW 5.8 7.8 3.9-6.4WNW30.17- 57.4 59.7----
2026-07-12 12:00 pm N 3.9 5.8----30.17-0.01 57.4 59.5----
2026-07-12 11:50 am N 3.9 5.8 4.3 96.5WNW30.16- 57.4 59.5----
2026-07-12 11:40 am N 1.9 3.9 4.3-6.5WNW30.17- 57.4 59.5----
2026-07-12 11:30 am N 1.9 3.9----30.17- 57.4 59.4----
2026-07-12 11:20 am N 1.9 3.9 4.6 86.3WNW30.17- 57.2 59.2----
2026-07-12 11:10 am N 1.9 3.9 4.6-6.3WNW30.16- 57.0 58.8----
2026-07-12 11:00 am N 3.9 3.9----30.16-0.01 56.8 58.3----
2026-07-12 10:50 am N 1.9 3.9 4.6 96.3WNW30.16- 57.4 58.3----
2026-07-12 10:40 am- 0.0 1.9----30.16- 57.9 57.9----
2026-07-12 10:30 am- 0.0 1.9----30.17- 58.1 57.7----
2026-07-12 10:20 am- 0.0 1.9 4.6 86.3WNW30.18- 57.6 57.7----
2026-07-12 10:10 amSSE 1.9 1.9----30.18- 57.4 57.6----
2026-07-12 10:00 am- 0.0 1.9----30.18+0.01 57.6 57.4----
2026-07-12 09:50 am- 0.0 1.9 4.6 86.2WNW30.18- 57.4 57.2----
2026-07-12 09:40 am SE 1.9 3.9 4.6-6.2WNW30.18- 57.0 57.2----
2026-07-12 09:30 am SE 3.9 3.9----30.18- 56.7 57.2----
2026-07-12 09:20 am SE 3.9 5.8 4.9 86.1 NW30.18- 56.7 57.2----
2026-07-12 09:10 am SE 3.9 5.8 4.9-6.1 NW30.18- 56.7 57.2----
2026-07-12 09:00 amESE 3.9 5.8----30.18+0.03 56.7 57.0----
2026-07-12 08:50 amESE 3.9 5.8 4.9 106.4WNW30.18- 56.8 57.0----
2026-07-12 08:40 amESE 3.9 5.8 4.9-6.4WNW30.17- 56.8 57.0----
2026-07-12 08:30 amESE 3.9 3.9----30.17- 56.8 57.0----
2026-07-12 08:20 am SE 3.9 3.9 5.2 96.6WNW30.17- 56.8 57.0----
2026-07-12 08:10 am SE 1.9 3.9 5.2-6.6WNW30.18- 56.8 57.0----
2026-07-12 08:00 amESE 1.9 3.9----30.17+0.04 56.7 56.8----
2026-07-12 07:50 amESE 3.9 5.8 4.6 86.3WNW30.17- 56.7 56.8----

Wave Summary
for 46029 as of (8:10 am PDT)
1510 GMT on 07/13/2026:

These wave data are displayed in rounded times.

     

Click on the graph icon in the table below to see a time series plot of the last five days of that observation.

5-day plot - Significant Wave Height Significant Wave Height (WVHT): 3.6 ft
5-day plot - Swell Height Swell Height (SwH): 2.6 ft
5-day plot - Swell Period Swell Period (SwP): 7.1 sec
5-day plot - Swell Direction Swell Direction (SwD): NW
5-day plot - Wind Wave Height Wind Wave Height (WWH): 2.3 ft
5-day plot - Wind Wave Period Wind Wave Period (WWP): 5.3 sec
5-day plot - Wind Wave Direction Wind Wave Direction (WWD):WNW
5-day plot - Wave Steepness Wave Steepness (STEEPNESS): AVERAGE
5-day plot - Average Wave Period Average Wave Period (APD): 4.5 sec
Previous observations
TIME
(PDT)
5-day plot - Wave Height
WVHT
ft
5-day plot - Swell Height
SwH
ft
5-day plot - Swell Period
SwP
sec
5-day plot - Swell Direction
SwD
 
5-day plot - Wind Wave Height
WWH
ft
5-day plot - Wind Wave Period
WWP
sec
5-day plot - Wind Wave Direction
WWD
 
5-day plot - Wave Steepness
STEEPNESS
 
5-day plot - Average Wave Period
APD
sec
2026-07-13 07:40 am 3.6 2.6 7.7 NW 2.6 5.9 NW AVERAGE 4.4
2026-07-13 07:10 am 3.6 2.6 8.3WNW 2.3 5.6 WNW AVERAGE 4.8
2026-07-13 06:40 am 3.6 3.0 7.1WNW 2.3 5.6 WNW AVERAGE 4.9
2026-07-13 06:10 am 3.6 2.6 8.3WNW 2.3 3.8 NW AVERAGE 4.7
2026-07-13 05:40 am 3.6 3.0 8.3WNW 2.3 5.3 NW AVERAGE 5.0
2026-07-13 05:10 am 3.6 3.0 7.7WNW 2.3 5.0 WNW AVERAGE 5.2
2026-07-13 04:40 am 4.3 3.3 7.7WNW 2.6 5.6 WNW AVERAGE 5.3
2026-07-13 04:10 am 3.9 3.3 7.7WNW 2.3 5.0 WNW AVERAGE 5.1
2026-07-13 03:40 am 4.3 3.3 8.3WNW 2.3 5.3 WNW AVERAGE 5.3
2026-07-13 03:10 am 4.3 3.6 7.1WNW 2.3 5.0 WNW STEEP 5.3
2026-07-13 02:40 am 4.3 3.6 8.3WNW 2.3 4.8 WNW AVERAGE 5.4
2026-07-13 02:10 am 4.3 3.9 8.3 NW 2.3 5.0 WNW AVERAGE 5.6
2026-07-13 01:40 am 4.9 4.3 7.7WNW 2.3 4.5 NW AVERAGE 5.7
2026-07-13 01:10 am 4.9 4.3 9.1 NW 2.3 4.5 WNW AVERAGE 5.7
2026-07-13 12:40 am 5.2 4.6 7.7WNW 2.3 4.3 WNW AVERAGE 5.8
2026-07-13 12:10 am 4.9 4.3 8.3WNW 2.3 4.8 WNW AVERAGE 5.6
2026-07-12 11:40 pm 4.6 3.9 9.1 NW 2.6 4.8 WNW SWELL 5.6
2026-07-12 11:10 pm 4.9 4.3 8.3WNW 2.3 5.3 W AVERAGE 5.7
2026-07-12 10:40 pm 4.9 4.3 8.3WNW 2.3 5.0 W AVERAGE 5.8
2026-07-12 10:10 pm 4.6 3.9 9.1 NW 2.6 4.2 WNW SWELL 5.6
2026-07-12 09:40 pm 4.6 3.9 9.1 NW 2.6 5.6 WNW SWELL 5.5
2026-07-12 09:10 pm 4.6 3.6 9.1WNW 2.6 3.7 NNW SWELL 5.3
2026-07-12 08:40 pm 4.6 3.6 9.1 NW 2.6 3.7 NNW SWELL 5.6
2026-07-12 08:10 pm 4.3 3.6 9.1WNW 2.6 5.9 W SWELL 5.2
2026-07-12 07:40 pm 4.3 3.6 9.1WNW 2.6 5.9 W SWELL 5.2
2026-07-12 07:10 pm 4.3 3.6 9.1WNW 2.3 3.6 NW SWELL 5.1
2026-07-12 06:40 pm 4.3 3.6 9.1WNW 2.3 3.2 NNW SWELL 5.3
2026-07-12 06:10 pm 4.6 3.9 9.1WNW 2.3 3.1 NNW SWELL 5.2
2026-07-12 05:40 pm 4.3 3.6 9.1 NW 2.0 2.9 NNW SWELL 5.2
2026-07-12 05:10 pm 3.9 3.6 9.1 NW 1.6 5.0 WNW SWELL 5.6
2026-07-12 04:40 pm 3.9 3.6 9.1 NW 1.6 5.3 WNW SWELL 5.4
2026-07-12 04:10 pm 3.9 3.6 9.1 NW 1.6 4.3 WNW SWELL 5.8
2026-07-12 03:40 pm 4.3 3.9 9.1 NW 1.6 5.9 WNW SWELL 6.7
2026-07-12 03:10 pm 4.6 4.3 9.1WNW 1.6 5.6 WNW SWELL 7.3
2026-07-12 02:40 pm 4.3 3.9 9.1 NW 1.3 4.8 NW SWELL 6.9
2026-07-12 02:10 pm 3.9 3.9 9.1WNW 1.3 5.0 NW SWELL 6.9
2026-07-12 01:40 pm 4.3 3.9 9.1WNW 1.3 4.3 WNW SWELL 6.9
2026-07-12 01:10 pm 3.9 3.9 9.1 NW 1.0 3.8 WNW SWELL 6.6
2026-07-12 12:40 pm 4.3 3.9 10.0 NW 1.0 3.6 WNW SWELL 6.5
2026-07-12 12:10 pm 3.9 3.9 8.3WNW 1.0 3.6 W AVERAGE 6.4
2026-07-12 11:40 am 4.3 4.3 9.1WNW 1.0 3.6 W SWELL 6.5
2026-07-12 11:10 am 4.6 4.3 8.3WNW 1.3 3.7 WNW AVERAGE 6.3
2026-07-12 10:40 am 4.6 4.6 9.1WNW 1.3 3.6 WNW SWELL 6.3
2026-07-12 10:10 am 4.6 4.3 8.3WNW 1.3 3.8 W AVERAGE 6.3
2026-07-12 09:40 am 4.6 4.3 8.3WNW 1.3 4.0 W AVERAGE 6.2
2026-07-12 09:10 am 4.9 4.6 7.7 NW 1.3 3.8 W AVERAGE 6.1
2026-07-12 08:40 am 4.9 4.6 10.0WNW 1.3 3.8 WSW SWELL 6.4
2026-07-12 08:10 am 5.2 4.9 9.1WNW 1.3 3.6 WSW AVERAGE 6.6

Plot icon Plot of wave energy versus frequency (and period)