Issue with WeeWX Forecast - XTide Thread

[Rory Gillies]

Hi,

I am trying to add tides to my ephemeris page on my website but having difficulty getting it to work. I'm not at the stage of adding he code to my page template yet as I can't seem to get valid tide data. I am running forecast version 3.4.0b12. I have the nonfree data installed and XTide is working:

weewx@weather:$ sudo tide -l "Lerwick"
Indexing /usr/share/xtide/harmonics-dwf-20100529-nonfree.tcd...
Indexing /usr/share/xtide/harmonics-initial.tcd...
Indexing /usr/share/xtide/harmonics-dwf-20191229-free.tcd...
Lerwick, Shetland Islands, Scotland - READ flaterco.com/pol.html
60.1540° N, 1.1403° W

2023-05-22  1:32 PM BST   1.83 meters  High Tide
2023-05-22  7:21 PM BST   0.66 meters  Low Tide
2023-05-22  9:52 PM BST   Sunset
2023-05-23  1:40 AM BST   1.91 meters  High Tide
2023-05-23  2:17 AM BST   Moonset
2023-05-23  4:08 AM BST   Sunrise
2023-05-23  5:38 AM BST   Moonrise
2023-05-23  7:52 AM BST   0.49 meters  Low Tide
2023-05-23  2:12 PM BST   1.72 meters  High Tide
2023-05-23  7:56 PM BST   0.76 meters  Low Tide
2023-05-23  9:55 PM BST   Sunset
2023-05-24  2:16 AM BST   1.84 meters  High Tide....>

When WeeWX restarts I can see the XTide thread:

May 22 08:56:52 weather weewx[1048507] INFO user.forecast: MainThread: XTide: forecast version 3.4.0b12
May 22 08:56:52 weather weewx[1048507] INFO user.forecast: MainThread: XTide: interval=1800 max_age=2419200 location='Lerwick, Shetland Islands, Scotland' duration=3600

But when it generates a report it reports no tidal events:

May 22 09:35:18 weather weewx[1048507] INFO user.forecast: XTideThread: XTide: generating tides from 2023-05-22 00:00:00 BST (1684710000) to 2023-05-22 01:00:00 BST (1684713600)
May 22 09:35:18 weather weewx[1048507] INFO user.forecast: XTideThread: XTide: got no tidal events

For some reason it appears to be generating tides from the past, and between midnight and 01:00, where is it getting this time range from?

Here's the [Forecast] section in weewx.conf:

[Forecast]
    data_binding = forecast_binding
    interval = 1800
    [[XTide]]
        location = "Lerwick, Shetland Islands, Scotland"
    [[Zambretti]]
        hemisphere = NORTH
    [[Aeris]]
        client_id = xxxxxxxxxxxxxxxxxxxxxx
        client_secret = xxxxxxxxxxxxxxxxxx
    [[WU]]
        api_key = xxxxxxxxxxxxxxxxxxxxxxxx
    [[UKMO]]
        api_key = xxxxxxxxxxxxxxxxxxxxxxxx
        location = 352262

And here's the [Services] section:

 [[Services]]

 archive_services = weewx.engine.StdArchive, user.forecast.ZambrettiForecast, user.forecast.NWSForecast, user.forecast.WUForecast, user.forecast.OWMForecast, user.forecast.UKMOForecast, user.forecast.AerisForecast, user.forecast.WWOForecast, user.forecast.DSForecast, user.forecast.XTideForecast

All other forecast threads are working correctly, just the XTide thread with the issue. If I use the bundled tides.html it reports "Tide forecast is not available."

Any ideas?

[Rory Gillies]

OK, I sussed it out by adding duration = 1209600 to the XTide section. I thought this was the default value as it is commented out in forecast.py but it needs to be there for it to work.

Now I have the tides the heights are showing up in feet, not metres, any idea how to change this?

Thanks,

Rory

[Rory Gillies]

Not an elegant solution but I just converted the feet to metres:

#set $tides = $forecast.xtides
#if len($tides) > 0
  #for $tide in $tides  
  #set $height=$tide.offset.raw / 3.281
<tr>
   <td>$tide.event_ts.format("%a %d %H:%M")</td>
   <td>$tide.hilo</td>
   <td>
   #echo '%.2f' % $height
   m</td>
</tr>
#end for

Produces:

Mon 22 19:21 L 0.66 m
Tue 23 01:40 H 1.91 m
Tue 23 07:52 L 0.49 m
Tue 23 14:12 H 1.72 m
Tue 23 19:56 L 0.76 m
Wed 24 02:16 H 1.84...