Wave Heights

[tmagan]

In the attachment, I plotted wave heights around Florida, what units are the wave heights in?

[Greg Higgins]

Where did you getyour data? URL???

[tmagan]

Where did you getyour data? URL???

http://www.atmos.albany.edu/weather/dat ... @H_boy.wmo

[Greg Higgins]

Your answer is: meters

[tmagan]

Your answer is: meters

Well,
I have 'English' in my Station Plot Preference units, which would make some of the waves in the above map over 100 feet.

[LaurierWilliams]

Your answer is: meters

Well,
I have 'English' in my Station Plot Preference units, which would make some of the waves in the above map over 100 feet.

You've up-converted it twice. DA will take the original observation (in metres) and convert it to feet. I've just done a quick test on current (09z 19 Nov 2012) data, and wave heights in the Gulf when plotted using "English" units are mostly between 13 and 25 feet. Change to metric units, replot and the heights change back to less than one-third, as they should. When you drew your chart stations in the Gulf were reporting light to moderate N to NE winds with a light pressure gradient, a little steeper near the US southern coast [http://www.australianweathernews.com/ch ... _15-21.gif] and the wave heights look about right for that situation.

For reference, the largest rogue wave scientifically recorded in open water was 29.1m (95 feet) west of Scotland in February 2000 [http://en.wikipedia.org/wiki/Rogue_wave]. Tsunami waves get a bit bigger - this report [http://www.surfersvillage.com/surfing-n ... KoGveSvGqg] suggests 1740 feet as part of the Alaskan quake of 1958.

[tmagan]

Let me try it this way for data on 0200Z November 20th. On the map I have highlighted Buoy 41009. According to http://www.ndbc.noaa.gov/station_page.php?station=41009, the wave height reported at that time are 2.9 meters, or 9.5 feet. None of the two maps below, with arrows pointing to Buoy 41009 have wave heights anywhere near those two numbers, the first using metric station plot units, the second using English station plot units.

[Greg Higgins]

Did a little research for you. Here is the link to buoy data format: http://www.nodc.noaa.gov/General/NODC-Archive/f291.html


Here is the raw data for 41009 at 0200Z November 20th

****the raw data file from http://www.atmos.albany.edu/weather/dat ... @H_boy.wmo IS CORRUPT************
this is ALL the data in that file, so I'm guessing DA is using a different data set.

323

SNCA26 KWBC 202000 RRZ

AAXX 19201

78090 15/// /0000 30147 60041 92000=



I pulled the raw data from http://www.atmos.albany.edu/weather/dat ... @H_boy.wmo for

41009 19121 99285 70802 46/// /3310 10182 20156 40194 91220 22200

00253 333 91213 555 11110 22115 31146 43214 61219 329103 325105

328106 325102 325106 325109=



This is from: http://www.ndbc.noaa.gov/station_page.php?station=41009

Conditions at 41009 as of
(9:50 pm EST on 11/19/2012)
0250 GMT on 11/20/2012:


Wind Direction (WDIR): NNW ( 330 deg true )

Wind Speed (WSPD): 23.3 kts

Wind Gust (GST): 27.2 kts

Wave Height (WVHT): 9.5 ft

Dominant Wave Period (DPD): 11 sec

Average Period (APD): 6.2 sec

Mean Wave Direction (MWD): NE ( 46 deg true )

Atmospheric Pressure (PRES): 30.02 in

Pressure Tendency (PTDY): -0.02 in ( Falling )

Air Temperature (ATMP): 68.9 °F

Water Temperature (WTMP): 78.3 °F

Dew Point (DEWP): 64.4 °F

Wind Speed at 10 meters (WSPD10M): 25.3 kts




You would need to decide which of the data sets is being used and then compare raw data to see if they match up. I had originaly looked on Albany's page and found where they stated the data was in meters but the page you provided says feet, but it still didn't match up to your pics. Confusing, maybe TIm or someone else can jump in.

[LaurierWilliams]

AAXX 19201 41009 19121 99285 70802 46/// /3310 10182 20156 40194 91220 22200

00253 333 91213 555 11110 22115 31146 43214 61219 329103 325105

328106 325102 325106 325109=

I think it would have to be a SYNOP code dataset, as above, in which case it would be the same regardless of source. Unfortunately, the wave data in this observation is in one of the national coded sections. I've italicized or coloured four parts of the code.

19201 indicates 19th day, 20th hour, wind speeds measured and in metres/second. If the wind is measured in m/s rather than knots, it would seem unusual to report wave heights in other than metric.
22200 00253 is Section 2 where international-exchange wave data is normally put, but there is none there. 22200 just says Section 2, vessel stationary, and 00253 is water temperature 25.3.
333 91213 says this is Section 3 (international exchange) but 91213 is for a nationally developed code which I don't have.
Finally everything after 555 is national code only, which again I don't have.

Does any US resident know the US nationally developed SYNOP codes or where they can be found?

[Greg Higgins]

The other thing to consider is that DA has not been updated in years and some of the data formats and URL's have changed rendering DA inaccurate or "broken".