Station 46041 (LLNR 733) - CAPE ELIZABETH - 45NM NW of Aberdeen, WA Image indicating link to RSS feed of recent meteorological observations for station 46041


Conditions at 46041 as of
(1:00 am PDT)
0800 GMT on 05/23/2026:
     

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): NW ( 320 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 13.6 kts
5-day plot - Wind Gust Wind Gust (GST): 17.5 kts
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES):29.94 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY):+0.00 in ( Steady )
5-day plot - Air Temperature Air Temperature (ATMP): 52.2 °F
5-day plot - Dew Point Dew Point (DEWP): 51.1 °F
5-day plot - Wind Chill Wind Chill (CHILL): 47.3 °F
5-day plot - Wind Speed at 10 Meters Wind Speed at 10 meters (WSPD10M): 15.5 kts
5-day plot - Wind Speed at 20 Meters Wind Speed at 20 meters (WSPD20M): 15.5 kts
5-day plot -  Wind Speed, Wind Gust and Atmospheric Pressure Combined plot of Wind Speed, Gust, and Air Pressure
Supplemental Measurements
Highest 1-minute Wind Speed
Time (PDT)5-day plot - 1-Minute Wind Speed WSPD 5-day plot - 1-Minute Wind Direction WDIR
12:58 am 15.5 kts-
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
2026-05-23 12:50 am NW 13.6 19.4 6.2 105.7WNW29.94- 52.2- 51.1---
2026-05-23 12:40 am NW 13.6 17.5 6.2-5.7WNW29.94- 52.3- 51.1---
2026-05-23 12:30 amNNW 11.7 15.5----29.95- 52.3- 51.1---
2026-05-23 12:20 am NW 13.6 19.4 5.9 105.7WNW29.95- 52.3- 51.1---
2026-05-23 12:10 amNNW 13.6 17.5 5.9-5.7WNW29.94- 52.5- 51.4---
2026-05-23 12:00 amNNW 13.6 17.5----29.94+0.00 52.5- 51.4---
2026-05-22 11:50 pm NW 15.5 19.4 6.2 105.8WNW29.95- 52.5- 51.4---
2026-05-22 11:40 pm NW 15.5 19.4 6.2-5.8WNW29.94- 52.5- 51.4---
2026-05-22 11:30 pmNNW 15.5 19.4----29.94- 52.5- 51.4---
2026-05-22 11:20 pmNNW 15.5 19.4 5.9 75.5 NW29.94- 52.5- 51.6---
2026-05-22 11:10 pmNNW 13.6 17.5 5.9-5.5 NW29.94- 52.7- 51.8---
2026-05-22 11:00 pm NW 13.6 17.5----29.94+0.00 52.7- 52.0---
2026-05-22 10:50 pm NW 15.5 21.4 5.6 105.3WNW29.94- 52.7- 51.8---
2026-05-22 10:40 pm NW 13.6 19.4----29.95- 52.9- 51.8---
2026-05-22 10:30 pm NW 15.5 19.4----29.95- 52.9- 51.8---
2026-05-22 10:20 pm NW 13.6 17.5 5.9-5.5WNW29.95- 53.1- 52.0---
2026-05-22 10:10 pm--- 5.9 85.5WNW--------
2026-05-22 10:00 pmNNW 13.6 17.5----29.95+0.00 53.1- 52.2---
2026-05-22 09:50 pm NW 13.6 19.4 5.9 95.7WNW29.95- 53.1- 52.2---
2026-05-22 09:40 pm NW 15.5 19.4 5.9-5.7WNW29.95- 52.9- 51.8---
2026-05-22 09:30 pmNNW 15.5 19.4----29.95- 52.9- 52.0---
2026-05-22 09:20 pm NW 15.5 19.4 5.6 105.4 NW29.94- 52.9- 51.8---
2026-05-22 09:10 pm NW 15.5 19.4----29.94- 52.7- 51.6---
2026-05-22 09:00 pm NW 15.5 19.4----29.94-0.02 52.7- 51.6---
2026-05-22 08:50 pm NW 13.6 19.4 5.9 105.7WNW29.94- 52.7- 51.6---
2026-05-22 08:40 pm NW 15.5 19.4----29.94- 53.1- 52.2---
2026-05-22 08:30 pm NW 15.5 19.4----29.94- 53.1- 52.2---
2026-05-22 08:20 pm NW 13.6 17.5 5.6 105.6WNW29.94- 52.9- 52.0---
2026-05-22 08:10 pmNNW 13.6 19.4 5.6-5.6WNW29.94- 52.9- 52.0---
2026-05-22 08:00 pm NW 15.5 21.4----29.94-0.04 53.1- 52.3---
2026-05-22 07:50 pm NW 15.5 17.5 6.2 105.6WNW29.94- 52.9- 52.3---
2026-05-22 07:40 pm NW 15.5 19.4----29.95- 52.7- 52.3---
2026-05-22 07:30 pm NW 15.5 19.4----29.95- 52.9- 52.5---
2026-05-22 07:20 pm NW 15.5 21.4 5.9 75.6 NW29.95- 52.5- 52.3---
2026-05-22 07:10 pm NW 15.5 19.4 5.9-5.6 NW29.95- 52.7- 52.7---
2026-05-22 07:00 pm NW 15.5 19.4----29.95-0.04 52.5- 52.5---
2026-05-22 06:50 pm NW 13.6 19.4 5.6 105.7 NW29.96- 52.7- 52.7---
2026-05-22 06:40 pm NW 13.6 17.5----29.96- 52.7- 52.7---
2026-05-22 06:30 pm NW 13.6 19.4----29.96- 52.7- 52.7---
2026-05-22 06:20 pmNNW 13.6 17.5 5.6 115.6WNW29.96- 52.5- 52.5---
2026-05-22 06:10 pm NW 11.7 15.5 5.6-5.6WNW29.96- 52.5- 52.5---
2026-05-22 06:00 pm NW 13.6 15.5----29.96-0.04 52.7- 52.7---
2026-05-22 05:50 pm NW 13.6 17.5 6.2 106.0WNW29.96- 52.7- 52.7---
2026-05-22 05:40 pmNNW 13.6 17.5----29.97- 52.5- 52.5---
2026-05-22 05:30 pm NW 13.6 17.5----29.97- 52.3- 52.3---
2026-05-22 05:20 pm NW 13.6 17.5 5.9 115.9WNW29.98- 52.7-----
2026-05-22 05:10 pm NW 13.6 17.5 5.9-5.9WNW29.98- 52.7-----
2026-05-22 05:00 pmNNW 13.6 17.5----29.98-0.03 52.5-----
2026-05-22 04:50 pm NW 13.6 17.5 5.6 105.8WNW29.98- 52.5-----
2026-05-22 04:40 pm NW 13.6 15.5----29.98- 52.7-----
2026-05-22 04:30 pm NW 13.6 17.5----29.98- 52.3-----
2026-05-22 04:20 pm NW 15.5 19.4 5.2 105.8WNW29.99- 52.2- 52.2---
2026-05-22 04:10 pm NW 13.6 19.4 5.2-5.8WNW29.99- 52.7- 52.7---
2026-05-22 04:00 pm NW 15.5 17.5----29.99-0.02 52.5- 52.5---
2026-05-22 03:50 pm NW 15.5 17.5 5.9 116.1WNW29.99- 52.3- 52.3---
2026-05-22 03:40 pm NW 13.6 17.5----29.99- 52.5-----
2026-05-22 03:30 pm NW 13.6 17.5----29.99- 52.5- 52.5---
2026-05-22 03:20 pmNNW 11.7 15.5 5.2 95.8WNW30.00- 52.5-----
2026-05-22 03:10 pm NW 13.6 17.5 5.2-5.8WNW29.99- 52.7- 52.7---
2026-05-22 03:00 pm NW 11.7 15.5----30.00-0.02 52.5- 52.5---
2026-05-22 02:50 pm NW 13.6 15.5 5.6 116.2WNW30.00- 52.5- 52.5---
2026-05-22 02:40 pmNNW 11.7 15.5----30.01- 52.7- 52.7---
2026-05-22 02:30 pmNNW 11.7 15.5----30.00- 52.7- 52.5---
2026-05-22 02:20 pmNNW 11.7 15.5 5.9 116.4WNW30.01- 52.9- 52.7---
2026-05-22 02:10 pm NW 11.7 15.5 5.9-6.4WNW30.01- 53.2- 53.1---
2026-05-22 02:00 pmNNW 11.7 15.5----30.01-0.01 53.2- 53.1---
2026-05-22 01:50 pm NW 11.7 15.5 5.6 116.4WNW30.01- 53.2- 53.1---
2026-05-22 01:40 pm NW 11.7 15.5----30.01- 53.4- 53.2---
2026-05-22 01:30 pm NW 11.7 13.6----30.01- 53.4- 53.1---
2026-05-22 01:20 pmNNW 11.7 13.6 5.2 76.2 NW30.01- 53.4- 53.1---
2026-05-22 01:10 pm NW 11.7 15.5 5.2-6.2 NW30.01- 53.4- 53.1---
2026-05-22 01:00 pm NW 11.7 13.6----30.01-0.01 53.4- 53.2---
2026-05-22 12:50 pm NW 11.7 13.6 5.6 106.3 NW30.01- 53.6- 53.2---
2026-05-22 12:40 pm NW 9.7 13.6----30.02- 53.6- 53.1---
2026-05-22 12:30 pmNNW 9.7 13.6----30.02- 53.4- 52.9---
2026-05-22 12:20 pm NW 11.7 13.6 5.6 106.3 NW30.02- 53.4- 53.1---
2026-05-22 12:10 pmNNW 9.7 11.7 5.6-6.3 NW30.02- 53.4- 53.1---
2026-05-22 12:00 pmNNW 9.7 11.7----30.02-0.01 53.2- 52.7---
2026-05-22 11:50 am NW 9.7 13.6 5.6 106.2WNW30.02- 53.2- 52.9---
2026-05-22 11:40 amNNW 9.7 13.6----30.02- 53.2- 52.9---
2026-05-22 11:30 amNNW 11.7 15.5----30.02- 53.4- 53.1---
2026-05-22 11:20 amNNW 9.7 11.7 5.2 116.2WNW30.02- 53.4- 53.1---
2026-05-22 11:10 amNNW 11.7 13.6 5.2-6.2WNW30.02- 53.2- 52.9---
2026-05-22 11:00 am NW 11.7 13.6----30.02+0.00 53.2- 52.9---
2026-05-22 10:50 amNNW 9.7 13.6 5.2 106.2WNW30.02- 53.2- 52.9---
2026-05-22 10:40 amNNW 11.7 15.5 5.2-6.2WNW30.02- 53.4- 53.2---
2026-05-22 10:30 am NW 9.7 15.5----30.02- 53.4- 53.2---
2026-05-22 10:20 am NW 9.7 11.7 5.2 106.0 NW30.02- 53.4- 53.2---
2026-05-22 10:10 amNNW 11.7 13.6----30.02- 53.4- 53.4---
2026-05-22 10:00 amNNW 11.7 13.6----30.02+0.00 53.4- 53.4---
2026-05-22 09:50 am NW 11.7 13.6 5.6 106.0 NW30.03- 53.2- 53.2---
2026-05-22 09:40 am NW 9.7 13.6----30.03- 53.4- 53.4---
2026-05-22 09:30 am NW 11.7 15.5----30.03- 53.4- 53.4---
2026-05-22 09:20 am NW 11.7 13.6 5.9 116.2WNW30.03- 53.4- 53.4---
2026-05-22 09:10 am NW 11.7 15.5 5.9-6.2WNW30.03- 53.4- 53.4---
2026-05-22 09:00 am NW 11.7 15.5----30.03+0.02 53.6- 53.6---
2026-05-22 08:50 am NW 11.7 13.6 5.6 105.8WNW30.03- 53.4- 53.4---
2026-05-22 08:40 am NW 9.7 13.6----30.03- 53.6- 53.6---
2026-05-22 08:30 am NW 11.7 13.6----30.03- 53.4- 53.4---
2026-05-22 08:20 am NW 11.7 13.6 5.6 115.8 NW30.02- 53.4- 53.4---
2026-05-22 08:10 am NW 11.7 13.6 5.6-5.8 NW30.02- 53.6- 53.6---
2026-05-22 08:00 am NW 11.7 13.6----30.03+0.02 53.6- 53.4---
2026-05-22 07:50 am NW 11.7 13.6 5.9 115.7WNW30.02- 53.6- 53.4---
2026-05-22 07:40 am NW 11.7 15.5 5.9-5.7WNW30.02- 53.8- 53.4---
2026-05-22 07:30 am NW 11.7 17.5----30.02- 53.8- 53.4---
2026-05-22 07:20 am NW 11.7 15.5 5.6 65.6 NW30.02- 53.8- 53.4---
2026-05-22 07:10 am NW 13.6 15.5 5.6-5.6 NW30.02- 53.8- 53.2---
2026-05-22 07:00 amNNW 13.6 17.5----30.02+0.00 53.8- 53.2---
2026-05-22 06:50 am NW 13.6 17.5 5.6 75.6 NW30.02- 53.6- 53.1---
2026-05-22 06:40 am NW 13.6 17.5 5.6-5.6 NW30.02- 53.6- 53.1---
2026-05-22 06:30 am NW 13.6 17.5----30.01- 53.8- 53.2---
2026-05-22 06:20 am NW 11.7 13.6 5.6 75.4 NW30.01- 53.8- 53.2---
2026-05-22 06:10 amNNW 13.6 17.5 5.6-5.4 NW30.01- 53.8- 53.2---
2026-05-22 06:00 am NW 13.6 15.5----30.01-0.01 53.8- 53.2---
2026-05-22 05:50 am NW 13.6 15.5 5.9 105.5 NW30.01- 53.8- 53.2---
2026-05-22 05:40 amNNW 13.6 15.5----30.01- 54.0- 53.2---
2026-05-22 05:30 amNNW 15.5 19.4----30.01- 54.0- 53.1---
2026-05-22 05:20 amNNW 15.5 19.4 5.9 75.5 NW30.01- 54.1- 53.2---
2026-05-22 05:10 amNNW 15.5 21.4 5.9-5.5 NW30.01- 53.8- 52.5---
2026-05-22 05:00 am NW 15.5 19.4----30.01-0.02 54.0- 52.9---
2026-05-22 04:50 am NW 17.5 21.4 5.2 75.4 NW30.01- 54.0- 52.9---
2026-05-22 04:40 am NW 15.5 19.4----30.01- 54.0- 53.1---
2026-05-22 04:30 am-------29.99-------
2026-05-22 04:20 am NW 15.5 21.4 5.6 75.6 NW30.01- 54.0- 53.2---
2026-05-22 04:10 am NW 15.5 21.4 5.6-5.6 NW30.01- 54.1- 53.4---
2026-05-22 04:00 am NW 15.5 17.5----30.01-0.04 54.3- 53.4---
2026-05-22 03:50 am NW 15.5 19.4 5.2 75.7WNW30.01- 54.3- 53.4---
2026-05-22 03:40 am NW 13.6 17.5 5.2-5.7WNW30.01- 54.5- 53.6---
2026-05-22 03:30 am NW 13.6 17.5----30.01- 54.3- 53.4---
2026-05-22 03:20 am NW 13.6 15.5 4.9 105.5 NW30.02- 54.5- 53.6---
2026-05-22 03:10 am NW 11.7 15.5 4.9-5.5 NW30.02- 54.5- 53.8---
2026-05-22 03:00 am NW 13.6 15.5----30.02-0.04 54.3- 53.6---
2026-05-22 02:50 am NW 11.7 13.6 5.2 105.8WNW30.02- 54.3- 54.0---
2026-05-22 02:40 am NW 11.7 13.6----30.02- 54.3- 54.1---
2026-05-22 02:30 am NW 9.7 11.7----30.03- 54.3- 54.3---
2026-05-22 02:20 am NW 9.7 11.7 5.2 105.7WNW30.03- 54.5- 54.5---
2026-05-22 02:10 amNNW 9.7 11.7 5.2-5.7WNW30.03- 54.5- 54.5---
2026-05-22 02:00 amNNW 9.7 13.6----30.03-0.04 54.5- 54.5---
2026-05-22 01:50 amNNW 9.7 13.6 5.2 105.8WNW30.04- 54.7- 54.7---
2026-05-22 01:40 amNNW 9.7 11.7----30.04- 54.7- 54.5---
2026-05-22 01:30 amNNW 9.7 11.7----30.04- 54.7- 54.5---
2026-05-22 01:20 amNNW 9.7 13.6 4.9 115.5 NW30.04- 54.9- 54.5---
2026-05-22 01:10 amNNW 11.7 13.6 4.9-5.5 NW30.04- 54.9- 54.5---
2026-05-22 01:00 amNNW 11.7 15.5----30.05-0.02 54.9- 54.3---
2026-05-22 12:50 amNNW 13.6 17.5 5.2 105.7WNW30.05- 55.0- 54.5---

Wave Summary
for 46041 as of (12:40 am PDT)
0740 GMT on 05/23/2026:

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): 6.2 ft
5-day plot - Swell Height Swell Height (SwH): 4.3 ft
5-day plot - Swell Period Swell Period (SwP): 10.0 sec
5-day plot - Swell Direction Swell Direction (SwD):WNW
5-day plot - Wind Wave Height Wind Wave Height (WWH): 4.3 ft
5-day plot - Wind Wave Period Wind Wave Period (WWP): 6.7 sec
5-day plot - Wind Wave Direction Wind Wave Direction (WWD):WNW
5-day plot - Wave Steepness Wave Steepness (STEEPNESS): SWELL
5-day plot - Average Wave Period Average Wave Period (APD): 5.7 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
2026-05-23 12:10 am 5.9 4.6 10.0WNW 3.3 5.6 WNW SWELL 5.7
2026-05-22 11:40 pm 6.2 4.6 10.0WNW 3.9 3.7 WNW SWELL 5.8
2026-05-22 11:10 pm 5.9 3.6 10.0WNW 4.6 6.7 NW STEEP 5.5
2026-05-22 10:40 pm 5.6 3.6 10.0WNW 3.9 6.7 NW AVERAGE 5.3
2026-05-22 10:10 pm 5.9 3.9 8.3WNW 4.3 6.2 NW AVERAGE 5.5
2026-05-22 09:40 pm 5.9 4.3 9.1WNW 4.3 5.9 NW AVERAGE 5.7
2026-05-22 09:10 pm 5.6 3.6 10.0 NW 3.9 6.7 NW AVERAGE 5.4
2026-05-22 08:40 pm 5.9 3.9 10.0WNW 4.3 5.9 NW AVERAGE 5.7
2026-05-22 08:10 pm 5.6 4.3 10.0WNW 3.6 5.0 NW SWELL 5.6
2026-05-22 07:40 pm 6.2 4.3 10.0WNW 4.3 6.2 NW SWELL 5.6
2026-05-22 07:10 pm 5.9 3.6 10.0 NW 4.6 7.1 NW STEEP 5.6
2026-05-22 06:40 pm 5.6 3.9 10.0 NW 3.9 6.2 NW SWELL 5.7
2026-05-22 06:10 pm 5.6 4.3 10.8WNW 3.6 4.8 NW SWELL 5.6
2026-05-22 05:40 pm 6.2 4.9 10.0WNW 3.9 5.9 NW SWELL 6.0
2026-05-22 05:10 pm 5.9 4.6 10.8WNW 3.6 5.0 NW SWELL 5.9
2026-05-22 04:40 pm 5.6 4.3 10.0WNW 3.3 5.3 NW SWELL 5.8
2026-05-22 04:10 pm 5.2 3.9 10.0WNW 3.6 6.2 NW SWELL 5.8
2026-05-22 03:40 pm 5.9 4.3 10.8WNW 3.9 6.7 NW SWELL 6.1
2026-05-22 03:10 pm 5.2 4.3 9.1WNW 3.3 5.3 WNW AVERAGE 5.8
2026-05-22 02:40 pm 5.6 4.9 10.8WNW 3.0 5.9 NW SWELL 6.2
2026-05-22 02:10 pm 5.9 5.2 10.8WNW 2.6 5.3 NW SWELL 6.4
2026-05-22 01:40 pm 5.6 4.9 10.8WNW 2.6 4.5 WNW SWELL 6.4
2026-05-22 01:10 pm 5.2 4.6 7.1 NW 2.6 5.3 NW STEEP 6.2
2026-05-22 12:40 pm 5.6 4.9 10.0 NW 2.3 4.2 WNW SWELL 6.3
2026-05-22 12:10 pm 5.6 4.9 10.0 NW 2.0 4.8 NW SWELL 6.3
2026-05-22 11:40 am 5.6 4.9 10.0WNW 2.3 4.8 WNW SWELL 6.2
2026-05-22 11:10 am 5.2 4.9 10.8WNW 2.3 5.3 WNW SWELL 6.2
2026-05-22 10:40 am 5.2 4.9 10.0WNW 2.3 4.5 NW SWELL 6.2
2026-05-22 10:10 am 5.2 4.6 10.0 NW 2.6 4.5 NW SWELL 6.0
2026-05-22 09:40 am 5.6 4.9 10.0 NW 2.6 4.8 NW SWELL 6.0
2026-05-22 09:10 am 5.9 4.9 10.8WNW 3.0 4.5 NW SWELL 6.2
2026-05-22 08:40 am 5.6 4.9 10.0WNW 3.0 4.5 NW SWELL 5.8
2026-05-22 08:10 am 5.6 4.6 10.8 NW 3.0 5.3 NW SWELL 5.8
2026-05-22 07:40 am 5.9 4.6 10.8WNW 3.6 5.9 NW SWELL 5.7
2026-05-22 07:10 am 5.6 3.6 10.8 NW 4.3 6.2 NWVERY_STEEP 5.6
2026-05-22 06:40 am 5.6 4.3 6.7 NW 3.9 4.5 NW STEEP 5.6
2026-05-22 06:10 am 5.6 3.9 6.7 NW 3.9 5.9 NW STEEP 5.4
2026-05-22 05:40 am 5.9 3.9 10.0 NW 4.3 6.7 NW AVERAGE 5.5
2026-05-22 05:10 am 5.9 3.3 10.0 NW 4.9 6.7 NW STEEP 5.5
2026-05-22 04:40 am 5.2 3.3 10.0WNW 3.9 6.7 NW STEEP 5.4
2026-05-22 04:10 am 5.6 3.3 10.0WNW 4.6 7.1 NW STEEP 5.6
2026-05-22 03:40 am 5.2 3.9 7.1WNW 3.6 6.2 WNW STEEP 5.7
2026-05-22 03:10 am 4.9 3.9 10.0 NW 3.3 4.8 WNW SWELL 5.5
2026-05-22 02:40 am 5.2 4.3 10.0WNW 3.0 4.8 NW SWELL 5.8
2026-05-22 02:10 am 5.2 4.6 10.0WNW 2.3 4.3 WNW SWELL 5.7
2026-05-22 01:40 am 5.2 4.6 10.0WNW 2.6 4.0 WNW SWELL 5.8
2026-05-22 01:10 am 4.9 4.3 10.8 NW 2.6 4.5 NW SWELL 5.5

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