• Sailing is all about the Weather.

    Big into the exploration of Atlantic Hurricanes since Katrina came uninvited into his world, James (Jim) Gurley (JamesG161) has followed every Tropical Storm birthed in Atlantic, Gulf and Caribbean waters since. Being a boater, he knows that we often need more time to prepare than we get from the TV weather folk. Jim relies on the science of storm development to share early warning info with friends and fellow boaters.

    Early in 2018, Jim and John Shepard, (JSSailem) started to chat about the weather data available. John asked Jim to help forecast Pacific NW storms, and this morphed into discussions on weather forecasting.

    For John, sailing in the PNW is sometimes hit and miss. One day is ugly, then a string of beautiful days but no wind, followed by a series of blue-sky days and 12 knot breezes. Being ready for those great sailing days means you need to look to the Pacific Ocean and what is brewing. John has been into Pacific NW Weather since the 1970’s when his first PNW November storm hit bringing more than 40 days and 40 nights of continual rain.

    Together we want to share information, new APPs, safety, and thoughts about letting the weather help you. Identify some of the resources for sailors and help prepare you for your next sailboat outing.

    It is far better to go out on the water knowing what to expect in weather terms, than to be out on the water and see dark ominous clouds suddenly appear, unprepared.

Vessel Weather Radar Question

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bxdobs

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Mar 16, 2009
13
2 23.5 none
A Commercial Shrimp Boat sank last month during an overnight squall (45+ Knots) which came up in less than 5 minutes 0-45 ... the boat was on a Lake surrounded by Mountainous terrain roughly 2km wide at its last reported position. This Vessel was designed for Ocean Seas so a true mystery how it could be sunk by a lake squall.

Question: Would/Could Weather Radar work in the narrow confines of a lake surrounded by mountains?

Being this squall came down from a west slope not sure how much warning it might have provided ... having never used or looked at these devices, not sure what their capabilities are ... radar works off reflected radio waves so curious to know how they would react to a slopping shoreline? (as in determining weather reflection vs ground reflection)
 
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Captain Larry-DH

Captain Larry-DH

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Jun 14, 2010
2,350
Robertson & Caine 2017 Leopard 40 CT
I don’t know of any pleasure boat that would have the type of doppler radar capable of detecting a microburst of wind, or even if such a thing exists.
Doppler weather radar that’s used by weather services for detecting precipitation and atmospheric information is tuned specifically for this, with special software. Ships radar can detect precipitation, and doppler radar such as Raymarine offers might be able to also display direction of precipitation movement relative to the vessel, but it’s not capable of being an early warning system for the type of wind event you described.
I have the Raymarine doppler radar, but the doppler display is very simple - red targets are stationary or moving toward the boat, green shift indicates targets moving away, with green at the trailing edge. I’ve never tried to use it to track rain (I try to tune it out as clutter). As a costal sailor I get better rain movement information on my phone using weather apps.
 
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tfox2069

tfox2069

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Apr 8, 2011
772
Hunter 40 Deale, MD
Concur with what @Captain Larry-DH wrote. I also own a Raymarine doppler radar unit, and while it does have a "weather" setting (which just means it switches the radar settings to be more sensitive to weather in the atmosphere than objects on the water), I think it mostly is good for detecting the density of moisture/rain. This being my first season with it I haven't tried it yet with any summer thunderstorms to see if there's any detectable rotation to the moisture it detects; my guess is that's the only way you'd know how the wind was behaving. I'm surmising maybe some moisture depicted as green as it moves away from your position, and red as it advances toward you? Maybe someone has looked at their radar in a thunderstorm and can comment. At any rate, the apps on your phone depict a much more advanced weather radar in almost real time that's very readable, so I agree that's probably a better way to go. But I'm willing to learn!
 
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sailme88

sailme88

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Jan 19, 2010
1,294
Catalina 34 Casco Bay
I have no fewer than 4 weather radar APPs and several wind APPs.. Why? Interpretation, that's why. While the weather radar all get their raw feed from the NWS, the each employ their own algorithms. Always interesting to toggle from one site to another and see the different projected future radar picture. Somewhere in the middle is the actual weather.. This is just the radar.. then there is the weather forecast modeling.. Gee, what's the European models for today say???

A science with a lot of variables.....
 
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JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,770
Hunter 430 Waveland, MS
Captain Larry-DH said:
Ships radar can detect precipitation, and doppler radar such as Raymarine offers might be able to also display direction of precipitation movement relative to the vessel, but it’s not capable of being an early warning system for the type of wind event you described.
Click to expand
:plus::plus:

We have tracked Summer Squalls using that method.

It Works!

Jim...
 
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bxdobs

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Mar 16, 2009
13
2 23.5 none
Thanks everyone ... most responses appear to suggest APPS are the way to go ... but ... APPS DON'T work well on inland lakes! We are a couple of hundred miles inland from the Pacific Ocean where most weather app data is being collected ... local weather reports don't work well either ... several converging valleys can cause some extreme MICRO CLIMATE effects ... we can have a raging storm in one part of the lake and 3 miles away the lake can be quiet as a church mouse. Lake is 100 Miles long and 2 miles max width

Maybe I am asking the question the wrong way OR not understanding what these Radar units will provide ... was wondering what effect the mountainous terrain surrounding the lake would have on Marine Radar ... basically, would the radar software be smart enough to see any weather coming down the mountain slope ... or ... perhaps radar can only see rain ... I don't believe there was any rain that accompanied this squall
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,679
Beneteau Oceanis 37 Havre de Grace
bxdobs said:
Thanks everyone ... most responses appear to suggest APPS are the way to go ... but ... APPS DON'T work well on inland lakes! We are a couple of hundred miles inland from the Pacific Ocean where most weather app data is being collected ... local weather reports don't work well either ... several converging valleys can cause some extreme MICRO CLIMATE effects ... we can have a raging storm in one part of the lake and 3 miles away the lake can be quiet as a church mouse. Lake is 100 Miles long and 2 miles max width
Click to expand
Sorry I don’t have any experience with using a radar for weather, but to clarify on the apps - I use apps for looking at real time radar (at least when there’s a chance of storms). I’m not using it as a forecast tool, because on many days there’s just a general hit or miss chance of storms across the region. But the real time radar is not a forecast - it’s actual conditions. If you’re watching it you can see storm cells fire up and move, just as you’re hoping to see on your boat based radar, but without needing to worry about if you’ve configured everything right and if you can see over the next mountain.
 
tfox2069

tfox2069

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Apr 8, 2011
772
Hunter 40 Deale, MD
So you're really asking whether conventional radar can detect wind - not just the moisture which may accompany turbulent wind in a thunderstorm, for example.

The answer is no - they cannot. But they CAN detect particles being driven by the wind, with the sensitivity/type of radar determining the size of the particles it can detect and track. Here's a pretty good thread on the subject, even though it discusses aircraft radar.

weather - How does radar detect turbulence and wind speed? - Aviation Stack Exchange

As for the mountains, depending on the capability of the radar the return from the mountains may well obscure the return from the particles, since it would be much stronger. Heavy moisture will provide a better - and possibly impenetrable return, so you may be much more likely to see a return from moisture before seeing the mountains, than with wind without significant enough moisture in it.

P.S. - The ability of even Raymarine's latest Quantum radar to see particles in the air other than moisture is pretty limited. You can read lots of reports of fishermen who would like to use it to spot birds in the air, which indicate potential fishing spots, are unable to effectively use it for that purpose - its not sensitive enough. To see the particles as fine as those which are swirled by high winds you'd likely need FAA quality radars - big static installations - and they have to have at least two of those to detect wind shear in a given spot.
 
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bxdobs

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Mar 16, 2009
13
2 23.5 none
thanks that suggests that there would be no way to see something like this coming, even with marine Radar, especially late at night (DARK) ... when we are out on the lake, ONLY EVER IN DAYLIGHT HOURS, we constantly watch the water for wind lines that can warn of approaching winds ... 2 miles of lake typically provides us a few minutes warning ... last year one of these squalls hit us within seconds, almost knocking down our hunter 23..5 (water ballast) all sails up ... and that was just from a 24 Knot squall ... although we have a mountain top radar station about 10 miles from this lake we actually use the University of Washington State Radar ... BUT ... find it can only provide a big picture, and not the micro climate events that seem to just pop up out of nowhere
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,145
CAL 35 Cruiser #21 moored EVERETT WA
Let first look at the types of radar on small boats. Most systems of not have Doppler. Whose that do use a rudimentary design at low power. The NOAA systems are high power systems and they provide some wind response but it is limited to the power and the reflectivity of the elements. Wind is a poor reflective element. Precipitation is a stronger reflective element.

bxdobs said:
Question: Would/Could Weather Radar work in the narrow confines of a lake surrounded by mountains?
Click to expand
The typical radar system provided for pleasure boaters would not work well in the conditions you describe.
  1. The power is not strong enough to distinguish wind
  2. the wind would be masked by the surrounding mountains reflective signal.
  3. If the weather condition is just wind not precipitation the radar sensitivity level would unlikely register any change in condition.
Lastly I suspect no one would be willing to pay the cost nor have the room to equip a boat like the 23.5 with the type of radar that would be needed.

In Canada they call these winds
Williwaw - A stormy, cold wind that blows down mountains.
 
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