rough weather advice - Page 8

Ribomaniatic · 27 August 2009, 09:25

Plas Menai -
As a dinghy instructor I understand what experience the helmswoman would have had - plenty of low speed manoeverability and troll speed rib driving, some up to about 10 knots in short bursts but thats really all. PB2, especially if the qualification is done in calm waters is not a rough weather qualification - thats an advanced powerboat qualification skill. I know powerboat instructors as well who I have had to coach in rough weather ribbing.

I don't blame her and commend her for acknowledging her limitations and volunteering as an AI for the exercise and trying to turn back when it got rough. Her turning in rough seas in those waves in an apparently unfamiliar boat are outside her skills and abilities.

Her helming style is fine for low speed dinghy coaching and neither of the senior more experienced instructors corrected her. I strongly feel that the SIiC was to blame for the planning and his failure to spot the limitations of his instructors however I understand how this scenario could go wrong so easily. Him not checking casualties and the welfare of students is a grave error; this is taught as an instructor let alone an advanced powerboat instructor.

Our centre is based in the Medina and we don't run powerboat fun runs in the solent, we don't carry enough inflatible life jackets (150kn) we only have 50kn buoyancy aids.

We are obviously better than Plas Menai

neilda · 27 August 2009, 11:16

Quote:

Originally Posted by codprawn

Wind strength doesn't always = wave height. Some of the worst seas I have seen have been with a Force 2 - after a big blow and a strange tide condition.

Is there a way to predict sea conditions to prevent people heading out in awful seas?

I tend to look at the Met Office site, but wonder what others do.

Poly · 27 August 2009, 11:24

Quote:

Originally Posted by neilda

Is there a way to predict sea conditions to prevent people heading out in awful seas?

I tend to look at the Met Office site, but wonder what others do.

It is part of the shipping and inshore waters forecast. It takes the form WIND, SEA STATE, PRECIPITATION, VISIBILITY.

In my ikle boat Sea State needs to be Slight or Calm for me to want to go out. For bigger ribs Moderate is probably OK, Rough is unpleasant and anything worse is for the insane! However even the inshore waters forecast covers a huge area up to 12 NM out to sea - and can't take account of local "shelter" like islands, headlands etc. The longer the fetch (distance travelled by the wind across open sea) the bigger the waves are going to be. The weather in the preceeding days also affects the swell.

cuttlefish · 27 August 2009, 11:35

you have a lot of experience, if you want to go to the marina and always be able to go out (perhaps yo have mader an appointment with frtiends to do so, etc.), you need to buy something like Codprawn spoke of, or at the very least a semi-displacement or displacement boat. Of course, you will also have to change your thinking; speed reduction for one, and no wave hopping, for another.

"Is there a way to predict sea conditions to prevent people heading out in awful seas?"

alystra · 27 August 2009, 11:50

Quote:

Originally Posted by Polwart

It is part of the shipping and inshore waters forecast. It takes the form WIND, SEA STATE, PRECIPITATION, VISIBILITY.

In my ikle boat Sea State needs to be Slight or Calm for me to want to go out. For bigger ribs Moderate is probably OK, Rough is unpleasant and anything worse is for the insane! However even the inshore waters forecast covers a huge area up to 12 NM out to sea - and can't take account of local "shelter" like islands, headlands etc. The longer the fetch (distance travelled by the wind across open sea) the bigger the waves are going to be. The weather in the preceeding days also affects the swell.

As well as the inshore waters forecast there's the coastal forecast too, which is for (I think) 2 miles offshore and to a certain extent takes account of the islands and lochs (around here anyway). I interpolate between the two.

The Coastal is split into 6 hour periods. It does tend to give wind strengths of, say 2-7, but that's likely to be true depending on which side of the island you're on, or if you're in or outside of a loch. The more accurate time scale is very useful.

m chappelow · 27 August 2009, 12:15

thing is the uk has such a vairied coast line and in places can go from sheer cliffs to steep pebble beaches/ sheltered bays through to long flat sandyopen beaches with offshore reefs and all perhaps within a 10 /15 miles area and when say an inshore forecast area covers perhaps an 150 mile coast line area a lot is therefore down to local conditions and knowlege ,and experience ,,,though then in some cases as an old retired fisherman /lifeboat cox said to me once ,,the more you think you know about an area the more you realise that you dont in some weather conditions,
,

Poly · 27 August 2009, 12:29

Quote:

Originally Posted by alystra

As well as the inshore waters forecast there's the coastal forecast too, which is for (I think) 2 miles offshore and to a certain extent takes account of the islands and lochs (around here anyway). I interpolate between the two.

The Coastal is split into 6 hour periods. It does tend to give wind strengths of, say 2-7, but that's likely to be true depending on which side of the island you're on, or if you're in or outside of a loch. The more accurate time scale is very useful.

Thanks Alystra - I hadn't realised that there was actually a difference between the "coverage areas".

alystra · 27 August 2009, 12:33

Quote:

Originally Posted by polwart

thanks alystra - i hadn't realised that there was actually a difference between the "coverage areas".

jambo · 27 August 2009, 13:04

Quote:

Originally Posted by alystra

Ah Tony you old sea dog you!!

Billy

Ribomaniatic · 27 August 2009, 13:41

Quote:

Originally Posted by neilda

Is there a way to predict sea conditions to prevent people heading out in awful seas?

I tend to look at the Met Office site, but wonder what others do.

Best site for me is MagicSeaweed, a surf forecast for the British Isles which gives swell height, period, wind strength and sea temperature in a topographic map on an hourly moving basis with predictions for 96 hours, works well for me, not so good for solent but channel predictions work.

Met Office as well as localised weather stations and buoys (Boscombe Pier buoy, Bramblenet etc.) should give you a good idea. If in doubt call up the non emergency centre of a local lifeboat station if you are seriously unsure.

SeaSkills · 27 August 2009, 14:00

Quote:

Originally Posted by neilda

I tend to look at the Met Office site, but wonder what others do.

The Met Office posts High Seas warnings and Strong Wind warnings; http://www.metoffice.gov.uk/weather/..._forecast.html

(Generally more applicable to the Shipping Forecast areas, but useful information)

You could also visit one of the forecast sites that gives swell height, such as Magic SeaWeed; http://magicseaweed.com/UK-Ireland-Surf-Forecast/1/

If you're not familiar with the terms used, this is the key for wave height:

Calm <0.1m
Smooth 0.1 - 0.5m
Slight 0.5 - 1.25
Moderate 1.25 - 2.5
Rough 2.5 - 4
Very Rough 4 - 6
High 6 - 9
Very High 9 - 14
Phenomenal over 14m

I've been out once in a "phenomenal" sea (not in a RIB!!) and I didn't like it much. Advice to stop at "moderate" in a RIB is not a bad guide, but even moderate seas are likely to be uncomfortable (it's not just wave height that matters, it's the distance between the waves too) for boats of medium size. Remember also that when the wind and tide are in the same direction the sea surface will tend to be calmer than when the tide turns, so you need to plan for that.

As a very very simple rule-of-thumb for people who have passed Level 2 and are looking for guidance we suggest that if there are white horses on the water they check the tides again; if wind is against tide, consider waiting until the tide turns and the sea eases. If wind and tide are together, don't bother going out - it's only going to get worse.

codprawn · 27 August 2009, 14:27

Quote:

Originally Posted by rupert

you have a lot of experience, if you want to go to the marina and always be able to go out (perhaps yo have mader an appointment with frtiends to do so, etc.), you need to buy something like Codprawn spoke of, or at the very least a semi-displacement or displacement boat. Of course, you will also have to change your thinking; speed reduction for one, and no wave hopping, for another.

"Is there a way to predict sea conditions to prevent people heading out in awful seas?"

dotted around the UK are weather data buoys - there are numerous ways of accesing the info but the easiest is

http://www.xcweather.co.uk/

Just hover the mouse over a buoy - it will tell you current wave height. In the Bristol channel area you can look at the ones further west and get a rough idea of what is coming but it doesn't take account of local conditions.

There was a good episode of Coast on the Bristol Channel area - they mentioned the funelling effect which I have often mentioned but never heard mentioned before.

It is even worse in the Burry Estuary - 3,000 miles of Atlantic rollers being forced into very shallow waters.

About 2 years ago there was a massive swell that came in - hardly any wind but a few boats broke free in our harbour and about 400 yds of the new costal cycle path were completely washed away - looked like the aftermath of an earthquake. Of course the Victorian sea defences were fine.........

alystra · 27 August 2009, 14:27

Quote:

Originally Posted by jambo

Ah Tony you old sea dog you!!

Billy

Steady.

cuttlefish · 27 August 2009, 15:10

A very useful post, thanks.

One point, following your rule of thumb (which I find very wise), and namely:
"Advice to stop at "moderate" in a RIB is not a bad guide"

it makes you wonder which ribs you could use in a savage sea (presuming that ribs are excellent rescue vessels) - e.g. see the link that Codprawn posted in the fire rescue situation. Or is it just a case of any rib, so long as the driver is up to it?

Pablo · 27 August 2009, 16:10

I think he is talking more in terms of comfort. A rescue boat is not out there for fun.

As it has already been pointed out local conditions are very important. On some of the "offshore" (> 12NM) sites I go to we often get a 2m swell. The swell can have upto a 15m wave length. The wavelength is so long that you hardly notice a swell at all. On the windguru website when it gives wave height as 1.5m I know that is not a problem on some sites but I wouldn't go to others.

cuttlefish · 27 August 2009, 16:15

Sorry, I thught that he was talking about safety, capsizing, and survival. That was what I referred to.

neilda · 28 August 2009, 00:08

A couple of very useful links in XC weather and magic seaweed.

Thanks...

cuttlefish · 28 August 2009, 07:30

I can't see the buoys on the Xcwether site. I am using France as the country (for C.I.'s).

cuttlefish · 28 August 2009, 12:41

Codprawn. Just right for a rusticate like me.

Two of my favourite photos of Rhosilli - the spay is reaching the top of Worms head - about 200' high.

codprawn · 28 August 2009, 13:46

Quote:

Originally Posted by rupert

I can't see the buoys on the Xcwether site. I am using France as the country (for C.I.'s).

There is only one near you - it is the Channel islands light vessel - not much good for your local conditions but ideal if you are planning a trip across to the mainland - you can see exactly what it's like in the middle before you go!!!