WeatherFax ...

[rgleason]

Isn't this just a measurement for the distance between the isobars, which is translated into wind speed, based upon the barometric pressure differential. Once that is determined aren't there are other means of determining wind direction based upon the center of the low or high. We know the around a low in our hemisphere will have winds pointed at an angle from the isobar line about 15-30 degrees towards the center of the low, just like a hurricane.



Is there a way to determine what that angle is from the magnitude of the wind?

[rgleason]

I think we almost have this measurement tool available. Simply use the current measurement tool and note the distance. Then use the calculator_pi plugin to create the formula that David gave us and use that to enter the distance to get the wind speed.



Integrating these functions in a plugin would be the next step.

[Moo]

Originally Posted by BILLY_BUDD

Does this help? The flows are directional...so measure into low pressure and out of high pressure....and derive you hemisphere from you position....

No: I'm not talking about cyclonic of anticyclonic flow but the compass direction of the isobars ( and by how much it is curving ); drawing one measurement approximately perpendicular to the isobars will not give this information, to a very high resolution.

[Moo]

Billy_budd... just wondering which Billy Bud you are?

[BILLY_BUDD]

I agree...picking the gradient is more difficult especially in shore where the isobars direction are more variable...offshore they are more circular. So, some propose that you can know by looking at the isobars! I think as
an approximation of a dynamic system, you may not get it right (perfect) every time but given the vector of the weather system and your position you should understand your situation with a good feel for the magnitude.

I’ve toyed with some geometric approximations but they are not passing the simple, quick and dirty quotient. I think its possible to do some higher math but, that higher math effort runs the risk of alienating some.

Following up on Ricks question...the offset from true geostrophic wind is explained below with a discussion of Ekmann Spiral. Which applies to ocean currents as well as atmospheric ones.

To let the cat out of the bag, I think drawing a rectangle between isobars with some limits on the included angles to fault the process when the geometry is ambiguous. The midpoint would be the target point with a mean value derived from the two side directions + 30° Ekmanm (friction ) offset.

If it intrigues you? Fine! If you find yourself put off by codifying your seat of the pants judgement, or more comfortable with GRIB strategies where the interpolation is taken care of for you. That’s cool too!

I think the modern PC is capable of the analytics, FitzRoy was onto something when he started trending barometric pressure. I felt it was worthy of more thought last winter when I told my friends by cell phone...”you better be somewhere safe before the barometer on the bulkhead reaches xxxxx millibar. Trend it, we will have an idea how much time you have?

Finally, I apologize for thinking out loud, its a product of the digital forum method of collaborating....

PS In the open ocean with, relative to land, smooth surface roughness, it’s effect is less but probably handled just fine with GRIBS fore true blue water mariners.

Ekman spiral - AMS Glossary

[mackerel man]

After spending THREE SOLID DAYS I've given up hope of Installing the Weatherfax Plugin.

I've installed other plugins previously without drama but this one has me beat. It seems one has to be pretty technical to follow this procedure, I have tried over and over believe me.

I'm thinking maybe SOMEONE might be willing to take control of my Laptop (remote access) and just do it....PLEASE?

About to cross the Atlantic from Caribbean to UK non stop solo so would be nice to have weather forecasts!!

Please don't send me a link to the Weatherfax Plugin instructions page OR post links to other Weatherfax programmes. TIA 🙏

I'm running V4.8.4 Opencpn
Windows 10
Marine SSB/HF Radio is Icom M801-E input to Laptop via RS232/USB

[cagney]

Originally Posted by mackerel man

After spending THREE SOLID DAYS I've given up hope of Installing the Weatherfax Plugin.

I've installed other plugins previously without drama but this one has me beat. It seems one has to be pretty technical to follow this procedure, I have tried over and over believe me.

I'm thinking maybe SOMEONE might be willing to take control of my Laptop (remote access) and just do it....PLEASE?

About to cross the Atlantic from Caribbean to UK non stop solo so would be nice to have weather forecasts!!

Please don't send me a link to the Weatherfax Plugin instructions page OR post links to other Weatherfax programmes. TIA ��

I'm running V4.8.4 Opencpn
Windows 10
Marine SSB/HF Radio is Icom M801-E input to Laptop via RS232/USB

Just ignore all the complicated compile instructions.

What happens when you're installing this plugin?
https://github.com/rgleason/weatherf...ov42-win32.exe
Link from your screenshot.

If you want help you need to describe exactly what you have tried and what didn't work.



Thomas

[LeaseOnLife]

Originally Posted by mackerel man

...snip...
I'm running V4.8.4 Opencpn
Windows 10
Marine SSB/HF Radio is Icom M801-E input to Laptop via RS232/USB

Since you mention the type of radio you have. This plugin only takes audio, it will not tune your radio... below message is from the plugin:

[mackerel man]

Thanks for your response. A friend suggested I upgrade to the latest version (v.5.0) then the plugin procedure is simple...I did that and it installed easily ��

[rgleason]

The weatherfax files badly need updating to new current URL's that provide weatherfaxes. This is not going to be accomplished by one person, therefore please add in this thread any weatherfax urls for your area that you have working with weatherfax_pi.


There is a beta update of weatherfax for OpenCPN 5.1 Beta that has been tested on Windows and Ubuntu 18.04 Bionic, and the Noaa OPC files all download properly, but not many of the other URL's are current and result in 404 errors. Therefore we need to get the weatherfaxInternetRetrieval.xml updated!


The link to Cloudsmith repository is here (using a search for the weatherfax*tarballs)
If you wish to give it a try you can download the tarball.

[rgleason]

I notice that there is a problem with this version. Internet Retrieval downloads some faxes, Noaa OPC atlantic and pacific for example, but does not properly download

Goes for example https://tgftp.nws.noaa.gov/fax/evnt12.jpg
or the smaller tif version of
https://tgftp.nws.noaa.gov/fax/PJAA99.gif
The error shows as a URL error



Also Passageweather files fail, but they do exist.

[rgleason]

We need experienced help modifying and updating the weatherfaxinternetretrieval.xml file and the Schedules.xml file for weatherfax_pi


The OPC Ocean Prediction Center website https://ocean.weather.gov/index.php
is being used almost exclusively and http://www.opc.ncep.noaa.gov/
is not being used anymore.


There are very good sources on the ocean.weather.gov pages, but they may also need recalibration.


At the moment I do not have time to do this, so we need some user volunteers to pick up the task!


Also we need some users that can test the new plugin weatherfax recording capability and verify the Fax schedules in the xml.

[rgleason]

David's post on updating weatherfaxinternetretrieval

Here is an updated source file for the weatherfax plugin. Here is a video showing an install example. https://youtu.be/Ks4JwUYu84w Sorry.. would not allow xml, and changing extension, it was 300 bytes too big. the video will include a link when i sort this out. Here is the link: Get the needed update file here: https://www.starpath.com/downloads/W...tRetrieval.xml

[rgleason]

WeatherfaxUK no longer works, but this website metoffice.gov.uk/weather/maps-and-charts/surface-pressure has good b&w faxes, we just have to figure out how the images are numbered.
https://www.metoffice.gov.uk/weather...rface-pressure


We need to get this into weatherfaxinternetretrieval.xml
https://www.weathercharts.org/ may be something useful here, has good links too.
familiar website http://www1.wetter3.de/
English http://www1.wetter3.de/index_en.html


Jetstream Analysis http://squall.sfsu.edu/crws/jetstream.html

[rgleason]

WeatherfaxUK does work now, and we do have the wetter website, testing with the most recent Plugin Manager version Weatherfax 1.9.5.15 which has an updated WeatherfaxInternetRetrieval.xml and is available now in the master catalog, beta.


This version has been updated so that the OPC server works. There are still servers and specific faxes that are no longer available or need recalibration with the wizard, but most of the links and faxes are good.

Someone needs to go through the entire weatherfaxInternetRetrieval.xml and clean it up.

Meanwhile the UK Meto server has great potential for good color and b&w faxes, we just have to figure out the naming sequence and respond in the weatherfax program. Someone here may recognize how they are naming these images. Please advise how these numbers are created and assigned for this sequence of faxes.. Look at the file names (first the number and then I have added the Date & UTC to help. How is the fax number created? Someone may know this. Thanks.


Also we would be interested in any testing of the sound feature.