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Old 01-12-2018, 18:58   #1
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Help me get a handle on weather

A hypothetical problem, the images a real time now but I'm sitting at home practising.

We have dropped 6hpa in a short time and if I were betting I say it will drop more.

Looking at the other images it doesn't look like an issue.

What would you do.... what should I do.
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Old 01-12-2018, 19:08   #2
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Re: Help me get a handle on weather

Where are you relative to the low in your hypothetical situation? If you are in Brisbane then its just sit back watch.
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Old 01-12-2018, 19:11   #3
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Re: Help me get a handle on weather

This is for tomorrow but the forecast is for 30kn. Is it all caused by the trough?

The trough doesn't seem deep?
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Old 01-12-2018, 19:13   #4
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Re: Help me get a handle on weather

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Where are you relative to the low in your hypothetical situation? If you are in Brisbane then its just sit back watch.
Brisbane, roughly in the little green circle in the top image. The low is roughly 1800klms away.
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Old 01-12-2018, 19:40   #5
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Re: Help me get a handle on weather

I'm sitting at anchor up the Coomera River now down the road from you. I can't see anything to plan at this stage. Just wait and see how big it develops and if it develops a recognizable path.
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Old 01-12-2018, 20:38   #6
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Re: Help me get a handle on weather

Forgetting the low pressure system way up north, I'm looking at the barometer dropping here.

It's now dropped 8hpa in 7 hours.

Reading the books they say that's a sign to head off and keep going or seek shelter. Also the maps don't show the lines close together so I'm confused, 8hpa we should have crossed 2 lines by now.
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Old 01-12-2018, 22:16   #7
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Re: Help me get a handle on weather

10mb in 12 hrs
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Old 01-12-2018, 23:03   #8
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Re: Help me get a handle on weather

Ok, I thought you were concerned with the tropical low turning into a cyclone.
If you turn on the pressure isobars on windy.com you can visualize the change in pressure that you see. It lets you go back 12 hours or so and forward days.
The high near New Cal was affecting Brisbane area. It has moved east and the low in the Tasman is now more dominate in the area.
The marine met service has been calling for high wind warning from early this afternoon through Monday. 30kts+ from the north. So far it hasnt hit where I am.
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Old 02-12-2018, 09:58   #9
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Re: Help me get a handle on weather

Also where are you trying to get to? Are you hypothetically heading North/South/East etc? Pressing the Windy play button (bottom left corner) gives you a 10 day forecast and you can click on your intended route to get specific info/predictions for that point.
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Old 02-12-2018, 11:31   #10
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Re: Help me get a handle on weather

Dave, look at the 4 day from the bureau of meterology: it is predicted to be gone in two days. Today T. C. Owen is supposed to get to Cat. 2, then it is predicted to move towards land and dissipate. From the Qld. warnings, which will be updated around 10 a.m.

If you're wanting to go for a sail, N, 10-20 for today, go to Peel Is., and return tomorrow after the southerly comes in. (From the Moreton Bay forecast.)

If you're wanting to go to New Caledonia, well regard this one as a warning shot across your bows, and maybe go to NZ instead! and wait till it's gone.

If you still keep your boat in Manly, cyclones don't get there except as extra-tropical storms. If you've got a mooring up the river, then you might want to go hide out where flooding cannot be a problem, where you both have wind protection, and the water can spread out safely.

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Old 02-12-2018, 18:14   #11
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Re: Help me get a handle on weather

Thanks all, I'm not describing what I'm after very well.

I was thinking of when I'm in the gulf or the Kimberly or anywhere in the world outside of internet range, I would be keeping an eye on the barometer when one day it drops 10mb in 12hours like it did yesterday.

The books say i should I be looking for a place to hide or start running, none of the books say wait and see, they all say you are about to get smashed.

I guess what I was hoping for is, what would you do if you only had the barometer readings, nothing else and saw the barometer drop like that. How often does that happen when there is no threat.

I am not concerned about the cyclone, it's unfortunate it was on the map and has caught everyone's eye, just imagine it's not there
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Old 02-12-2018, 18:16   #12
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Re: Help me get a handle on weather

Quote:
Originally Posted by Dave_S View Post
A hypothetical problem, the images a real time now but I'm sitting at home practising.

We have dropped 6hpa in a short time and if I were betting I say it will drop more.

Looking at the other images it doesn't look like an issue.

What would you do.... what should I do.
Have a nice sail South from Queensland!.

We did.
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Old 02-12-2018, 19:06   #13
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Re: Help me get a handle on weather

Dave
I'm all over just imaging the cyclone isn't there. Works for me.

Your book about and weather and the barometer negelected to mention an unfortunate fact. As you get out of the higher and mid latitudes the delta between what is a low and what is a high becomes very small. This makes forecasting just using pressure difficult and less practical. You will get very significant weather change in the lower latitudes, ie nearer the equator, with way less pressure change than you just saw in Brisbane. Once you zero out the diurnal change tbere isn't much less. Of course if its a cycclone then the pressure drop will be seen - but so will wind. Crossing the South Pacific we didn't track pressure till we started our passage to New Zealand.
We started this trip at 48*N and there barometric pressure is meaningful.
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Old 03-12-2018, 22:11   #14
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Re: Help me get a handle on weather

Quote:
Originally Posted by Dave_S View Post
Thanks all, I'm not describing what I'm after very well.

I was thinking of when I'm in the gulf or the Kimberly or anywhere in the world outside of internet range, I would be keeping an eye on the barometer when one day it drops 10mb in 12hours like it did yesterday.

The books say i should I be looking for a place to hide or start running, none of the books say wait and see, they all say you are about to get smashed.

I guess what I was hoping for is, what would you do if you only had the barometer readings, nothing else and saw the barometer drop like that. How often does that happen when there is no threat.

I am not concerned about the cyclone, it's unfortunate it was on the map and has caught everyone's eye, just imagine it's not there
Hi, Dave,

It's always a good idea to have in mind a place to go with the best protection available for the area...

So, speaking for myself only, YES, 10 hP in 10 hrs. would get my attention. Where to go, and what to do.... Well, we have SSB, so we can receive the Bureau of Meteorology forecasts in text form as well as by listening to the broadcasts, so if it were a cyclone approaching, we would know that; we would know its position and predicted path, and we would head for safety. You can get gribs over SSB, too, and they also are of some use. If you have SatPhone, you also have access to the data from the internet, at a cost, of course, but you would likely hear of it before we would, because we are dependent on their broadcast schedules.

To me, heading for safety is never wasted. Even if you don't get bombed, wherever you get to you find something to be interested in, especially the clouds! The less info you have, the more you rely on the baro and the sky. There's an old saying, "Mackerel sky and mare's tails means tall ships wear short sails". It means that when you see clouds that look like brumby's tails when they're running top speed, it is a warning of a trough, front, or storm coming. The rate of drop, and the actual pressures tell you what you're expecting.

You could use a good mangrove creek, if it is wide enough for your boat, mangroves give good wind protection; but be wary of anywhere that could catch breaking waves, up a few zig zags is safer, and remember to allow for storm surge.

Ann
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