Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-05-2013, 19:32   #31
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Quote:
Originally Posted by estarzinger View Post
^^ Yes, Sky Eye is interesting. Because Jonathan was down in Ushuaia it was/is used down there alot (and by some volvo and vendee racers) but cruisers/sailors elsewhere are less familiar with it.

I have been lazy and invested less time learning its strengths and capabilities than I should have. Perhaps you should start a thread and educate us all?
To be honest Evans, I only used it for the three trips I did south from Ushuia to the peninsula. What I have written above is pretty what I remember about using it. I would love one but at the moment have other ways to spend the $2000 that skyeye costs (with baby no1 on the way shortly!). But I am surprised that alot more of the top end (money is no object) boats haven't got Skyeye or similar given that it gives you real time info before the weather office guys even get it, and often long before it becomes available on the web. in places like Antarctica satpics might not even be available anywhere unless you download them yourself from the satellite. The resolution is not really good enough to pick out individual squalls or ice, but can show areas to avoid or prepare for.

As I understand it the satellites are constantly broadcasting the images they see. If you are underneath one with the right antenna (a quadrifilar helix antenna), and a radio capable of receiving on 137-138 mhz FM you can pick the images yourself and display them on a screen. This is old technology that has been around for some time, But it now sounds like some of the cheap $20 digital TV usb dongles can be configured as a receiver so by building an antenna you are good to go at a very affordable price. I am sure it's not quite as simple as this but...

One issue with overlaying satpics onto gribs is that the times don't always overlay perfectly, gribs being every 3 or 6 hours and the satpics being totally random depending on when they pass overhead. Normally you just have to mentally shift everything to mesh properly. It would be nice to have a grib viewer that interpolated the gribs so you could mesh them accurately. And even allowed you to offset the gribs to get them to match to a low, or frontal feature properly. I guess one issue of doing it yourself is it might be very hard to mesh the satpics at all. I think the skyeye software uses the satellite ephemeris data to mesh them geographically with reasonable accuracy.

If there was an easy piece of software that could overlay an internet sourced satpic onto gribs for coastal stuff I would love to use it more, and refine skills in this area. As I said I am very keen to try a homebuilt one as Wayne is doing here . With some success it seems (I was talking to him recently). Wayne crewed for me on one of the trips south and was also impressed with the sky eye system we had aboard.
__________________

__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 14-05-2013, 19:45   #32
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Snowpetrel,
Thanks for the real world experiences!!! (and the cool pictures...)


And I REALLY appreciate your comments about knowing how to use the GRIB charts effectively....(and use of wefax in areas that they cover well...)
I hope this isn't lost amongst all the other (cool) stuff in your posting....
Quote:
Originally Posted by Snowpetrel View Post
I've had good success with just the gribs as well, though I often also use a cheap receiver or HF to get wx faxes in the Tasman where NZ and Aus still put out good weather faxes, despite occasional mumbles about doing away with the fax radio broadcasts.

With the gribs I have found it's very important to watch the consistency of the forecasts over time. If they are changing significantly from one forecast to the next you know the computer is unsure and the situation is dynamic, in this case it is wise to be very cautious.

If they are consistent (stable) you can be pretty comfortable with the accuracy (by and large). The Gribs seem to show this better than the regular human interpreted forecasts and weather faxes which try to smooth out these computer generated irregularities.

The gribs seemed to me to be much less accurate around the coast than far offshore. But with a bit of commonsense you can often guess what additional local effects might be if you are to remote for proper local forecasts.







And, just to be clear, directly receiving the APT transmissions from the polar-orbiting LEO's (LowEarthOrbiting Satellites) / NOAA sats, has been around a LONG time....
My first experience using it was in the early-mid 1980's...along with use of the L-Band GOES satellite data, images, (and other charts transmissions from them), etc....

And, I still occasionally see a turnstile antenna or (quadrafiller antenna), on an ocean-going sailboat.....and usually an INMARSAT-C antenna on the same boat as well...
Quote:
Originally Posted by Snowpetrel View Post
I have also used a Sky eye, and found it well worth it's space. It gives you the direct image downloaded from the satellite overhead, often before the met office gets them. By overlaying the satpic over the gribs you can get a very good idea of how accurate they are as far as low centres and frontal positions. It was also handy for forecasting clear days for shore trips. And brings the cloud patterns back into your forecasting, for example you can see if the cold front is Ana or a Kata type, and see how squally the cold pool behind it is. Also useful are the lee waves behind any islands or mountains, giving you an idea of cloud base height and wind direction.
I do LOVE satellites!!!!
This is a GREAT way to get real-time satellite imagery!!!
And, as you've already realized, this real-time Low Earth satellite imagery can be some of the best weather data available in some of the more remote areas!!!

But, in my opinion, using this (marketed as Sky Eye, as well as other models on the market), and overlaying it on GIRB charts, is not exactly easy for those not into hi-tech....and isn't the cheapest, nor least-complex approach around....
In the areas where other weather sources are non-existent, poor-quality, and/or unreliable, this is a GREAT way to get real-time weather data, but for most cruisers, it's a bit "too complex"....





Thanks again for posting your experiences!!!

Fair winds...

John
s/v Annie Laurie
__________________

__________________
ka4wja is offline   Reply With Quote
Old 14-05-2013, 19:53   #33
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,318
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

We used the sky-eye in Vanuatu to find and avoid the dreaded convergence zone--the weather can be crappy where you are and great 25 miles away, and the wfax and gribs just don't have that accuracy.

I think that if I was starting with a new boat and was going to do one ocean crossing, I'd probably go Iridium. If I planned to cruise for at least 5 years, I go with the SSB/ham rig.

I just don't understand Goboatingnow's aversion to radio nets. If you get on the morning VHF net and ask if anyone has an 8mm tap and die, you will probably get someone knocking on your hull in the next half-hour. On the Pacific Maritime net, one boat said that they were critically low on engine oil about 1200 miles from San Francisco. The problem was solved by a nearby boat on the net--try that on a sat-phone.

And for the guy who says both are just luxuries, check out the many threads on overdue boats.
__________________
donradcliffe is offline   Reply With Quote
Old 14-05-2013, 22:30   #34
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Quote:
Originally Posted by ka4wja View Post
But, in my opinion, using this (marketed as Sky Eye, as well as other models on the market), and overlaying it on GIRB charts, is not exactly easy for those not into hi-tech....and isn't the cheapest, nor least-complex approach around....
+1, And thanks John for the comprehensive list of weather sources, It's always good to have them all in one place.

I agree completely, for those on a budget it's very hard to beat weather fax on an old cheap computer with JV com or similar linked through the microphone/head phone jack to a simple HF receiver or secondhand SSB with a long wire antenna. This is part of my standard offshore delivery kit, as most often the HF on the boat I am delivering doesn't work properly. One day I might buy a satphone for my kitbag, as well...

Quote:
Originally Posted by donradcliffe View Post
We used the sky-eye in Vanuatu to find and avoid the dreaded convergence zone--the weather can be crappy where you are and great 25 miles away, and the wfax and gribs just don't have that accuracy.
Thanks for this info, very interesting to hear about it's use in the tropics. Downloading satpics is as much fun (or more!) as I had in the early days with a homemade demodulator downloading weatherfaxes at sea. I sometimes think it's all getting just to easy!

However I do love the way gribs very accurately give wind speeds rather than my crude estimates on a weatherfax chart, but they don't normally have fronts displayed, so both are useful. If you couple a weather chart with the voice forecast you can still get an excellent short term forecast. I still remember spending the evenings at sea plotting the voice data onto a crude map and figuring how best to work the fronts to my advantage. Back when laptops cost lots of money.

Another advantage of the gribs is being able to peer (through an often murky and very treacherous crystal ball) up to a week or more ahead. This is sometimes worse than useless and downright misleading, but is often all you have to go on, weather faxes normally only go out to +48 hours or so around here.There is a four day fax but it is only updated once a day at 1600 or so LT as opposed to the gribs updating every 6 hours or so.

I guess we also shouldn't forget the humble barometer, couple this with real world onsite observations of sky sea and swell, plus a few weather faxes and you have a pretty powerful set of tools to decide what just might be a brewing... A few times I have "found" a developing low before the met office has (I would much rather I hadn't found it!) particularly in more remote areas. Mind you forecasts are getting much much better as time goes on, so much so that we are much more likely to get caught unprepared by a unforecast development.

I also found these which might be useful, the Ship (to set the position adjust it in the http tag) and yacht actual observations from the past 12 hours or so, so while not a forecast it can give you a heads up of what others are getting at sea around you, probably most useful if you are actually in range of cheap internet, although Mikes Yotreps system is very clever and I think can be compressed and downloaded via pactor. Anybody know any better place where actual latest observations from volunteer observing ships can be obtained?

Saying all this a small part of me (fortunately easily suppressed) misses the old days when we set off, armed with only a long range forecast, and put up with the weather we got... But I am not sure I'd go back without a fight.
__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 25-05-2013, 09:16   #35
Registered User

Join Date: Jan 2013
Location: E Caribbean
Boat: Hunter Passage 42
Posts: 115
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

This might be the better way to ask a question. We're trying to figure out how to receive weather fax using an ipad and the Black Cat app. We don't even understand the headings on the schedule out of New Orleans. We understand and have found the frequencies and the map areas but -
Trans Time given as 0000/1200 is that those two times are between those times?
Rpm/IOC what does that mean?
Valid time what does that mean?
Could you please let us know? Thank you, thank you
__________________
nolagal is offline   Reply With Quote
Old 25-05-2013, 09:34   #36
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,866
Images: 4
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Quote:
Originally Posted by nolagal View Post
This might be the better way to ask a question. We're trying to figure out how to receive weather fax using an ipad and the Black Cat app. We don't even understand the headings on the schedule out of New Orleans. We understand and have found the frequencies and the map areas but -
Trans Time given as 0000/1200 is that those two times are between those times?
Rpm/IOC what does that mean?
Valid time what does that mean?
Could you please let us know? Thank you, thank you
Trans Time 0000/1200 -- the broadcast is sent twice: at 0000 and at 1200. 0000 is midnight UTC (Coordinated Universal Time AKA Greenwitch Mean Time AKA Zulu)

RPM/IOC -- these describe the speed and format of the weatherfax. Your software will probably recognize them automatically, or there may be a place to enter these values.

Valid Time -- This is when the forecast was or will be valid. In other words, the time that the chart is drawn for.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 25-05-2013, 09:39   #37
Registered User

Join Date: Jan 2013
Location: E Caribbean
Boat: Hunter Passage 42
Posts: 115
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Thank you so much. Seems so obvious once its explained. Now we'll see if we can actually download something. We're anchored in Placencia and it seems a good time to finally try and learn to use our SSB (after 6 years of owning it).
:-))
__________________
nolagal is offline   Reply With Quote
Old 25-05-2013, 09:40   #38
Registered User

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 3,537
Quote:
Originally Posted by nolagal View Post
This might be the better way to ask a question. We're trying to figure out how to receive weather fax using an ipad and the Black Cat app. We don't even understand the headings on the schedule out of New Orleans. We understand and have found the frequencies and the map areas but -
Trans Time given as 0000/1200 is that those two times are between those times?
Rpm/IOC what does that mean?
Valid time what does that mean?
Could you please let us know? Thank you, thank you
The transmission time links to the valid time, for instance the 48h at 18.45 is valid for 12.00 day after tomorrow. Rpm & ioc are to do with transmission, if you can see an image OK then don't worry about them. Or have a look here..
http://www.hffax.de/html/hauptteil_beginners_guide.html:-D

Edit - or wot Paul said
__________________
conachair is online now   Reply With Quote
Old 25-05-2013, 09:42   #39
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,866
Images: 4
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

One more thing -- remember, you generally have to tune a SSB receiver 1.9 KHz below the published frequency. This is because the published frequency is the center frequency of the FSK (Frequency Shift Keying) signal. Io receive it with a SSB radio we need to tune lower in frequency. If the receiver has USB or LSB selection it needs to be set for USB. USB = Upper Side Band, LSB = Lower Side Band. We use USB on the marine bands.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 25-05-2013, 16:16   #40
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Quote:
Originally Posted by nolagal View Post

Trans Time given as 0000/1200 is that those two times are between those times?
Read into each particular station info very carefully.

Some stations broadcast at all given frequencies at all given times, but some other stations may use different frequencies at different times. They may be broadcasting on one fqcy mornings, another fqcy evenings, etc.

b.
__________________
barnakiel is offline   Reply With Quote
Old 27-05-2013, 16:50   #41
Registered User

Join Date: May 2013
Location: Mystic
Boat: Sabre 38 mkII
Posts: 261
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Thanks to the OP for a comprehensive list of connectivity for weather..

At the shoestring end of the spectrum, can i suggest a used Grundig Satelit 800 to get an honourable mention along with those SSB receivers...yacht boy etc... it has outstanding performance along with an antenna ran up the flag halyard.
__________________
Mystic38 is offline   Reply With Quote
Old 29-05-2013, 12:23   #42
Registered User

Join Date: Jan 2013
Location: E Caribbean
Boat: Hunter Passage 42
Posts: 115
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

At the risk of sounding extremely inept I ask this question.
Once both audio ends are plugged in (to icon and iPad) should I still be hearing the fax tone from the icon? When audio buds are plugged into my iPhone all sound comes though the earplugs but with the icon I'm still hearing thr audio. Trying to figure out why the picture quality is so poor.
Thanks
__________________
nolagal is offline   Reply With Quote
Old 29-05-2013, 13:09   #43
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

If you are using audio cable then the loudspeaker working or not will not affect the picture.

I'd prefer to still hear the sound as I use the sound to tune into the fqcy. Otherwise the only thing that counts is if there is good signal in the cable.

Mind that inshore you are not likely to receive a clean radiofax. Especially in a marina.

b.
__________________
barnakiel is offline   Reply With Quote
Old 29-05-2013, 13:29   #44
Registered User

Join Date: Jan 2013
Location: E Caribbean
Boat: Hunter Passage 42
Posts: 115
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Thanks barnakiel, I'm not in a marina we are in the anchorage at Placencia. Think that's the problem? It seems not to make a difference whether the cable is plugged in or not. Picture is still unreadable actually doesn't look like a picture at all. The frequencies I'm using are 4316, 8502, 12788 (that's after the 1.9 adjustment). We've turned everything off but still no good.
This is sooooo frustrating but nice of you to help.
__________________
nolagal is offline   Reply With Quote
Old 29-05-2013, 14:09   #45
Registered User
 
LakeSuperior's Avatar

Join Date: Jan 2008
Boat: Teak Yawl, 37'
Posts: 1,581
Images: 7
Re: Obtaining Accurate Offshore/Hi-Seas Weather data/forecasts, while at sea

Most points have been made in CF in the past. So just to make one more point for the SatPhone camp...you can take a Satphone in the liferaft with you when your yacht is sinking. This cannot be done with a SSB.

One does not have to fumble around with bad atmospheric conditions to issue an SOS on an SSB under extreme duress.

We had US and UK marine emergency numbers preprogrammed into the Iridium. It would take 2 seconds to dial help. One cannot do this with an SSB.

We used prepaid SIM cards for our Iridium so no monthly charges.

We had a brand new ICOM SSB and a brand new Iridium on our 2 year trip. The SSB is still new as we found it a PIA to use.

Simplify your life and just download the GRIBS on a SatPhone. Almost zero learning curve.

We only used the Iridium offshore. Near land we relied on a 15 dB WIFI antenna for full web access.
__________________

__________________
LakeSuperior is online now   Reply With Quote
Reply

Tags
weather

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:52.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.