2017 Weather to the Azores

[barnakiel]

Following a similar thread from 2016 I thought it may be a useful idea to start monitoring the weather on the patch from the Caribbean towards the Azores.

I will try to repost NOAA / NWS material here on a regular basis, so that crews looking for quick access will have a timeline reference for this season. And crews sailing in the future may get a chance to get related reference material without long searches on the Internet.

I may also make some comments or repost views of my more experienced colleagues at wx agencies - the UK and the US wx offices tend to post their views prior to every hurricane season that may be of interest here.

Edit: link to the 2016 collection is here:
http://www.cruisersforum.com/forums/...-164774-6.html

Stay tuned,
barnakiel

[barnakiel]

As this season I started the thread early, I think there is enough time to link and post some info related to the subject.

My default statement is that April can be early and my default advice is, especially for smaller boats and/or non-professional crews, to cross not before mid-May and, preferably on a more direct route than the one referred to as via-Bermuda.

I am pasting and linking below to information related to my default views.

There are many valid reasons why a skipper may elect otherwise.

The images are from my copy of the Imray 100 chart which I recommend for any boat sailing across in either direction - there is a lot of most useful info on its reverse and the chart itself is an excellent planning and tracking aid that can live on the table during the crossings.

I believe the info in the chartlets, collected and edited by Don Street, is sourced mostly from NP136, which again is something few weather aware skippers will disregard in their route planning.

https://www.admiralty.co.uk/publicat...-for-the-world

And below the images from Imray 100 and links to things well worth a look prior to your departure.

April can be early:
https://icons.wxug.com/data/dhc_arch...s/at200301.gif

Tropical features distribution (or 'why June is not too late'):
Tropical Cyclone Climatology

Very best regards,
barnakiel

[barnakiel]

Browsing the web for relevant weather content, I came across this image.

The whole story is explained here:

We can only forecast the weather a few days into the future | Dr. Randal S. Olson

I think it is a fine graph and and the story is well worth reading.

It is as if to say that beyond 10 days' our forecasts are in some cases less reliable than some alternative methods. An extra spin is that some of these alternative methods are like alternative medicine. ;-)

I hope you will enjoy the image and maybe it will wrap your head around the whole forecasting thing too?

Cheers,
b.

[barnakiel]

This one is a present (April the 7th) 96hrs prediction at NWS NOAA.

It does not look like at this point the weather is doing any favour to those underway.

I will start re-posting NOAA wx maps and other related info here at around mid-April.

Cheers,
barnakiel

[barnakiel]

Today is April, 13.

48hrs forecast shows a complex but not dangerous scenario. Likely a very slow ride, or a motoring spell, for those already underway.

HOWEVER, I re-post this radiofax to show the possible dangers of relying on only one piece of information (as opposed to monitoring the situation daily while using many methods of graphical representation, even if these have the same source data!).

Because if you look at how the grib data represents the development you can see that there is about to happen a brief but fierce extra-tropical feature. Look at how low it will track before recurving. If it does happen, it may be one of those that wiped out boats and crews in previous seasons. See the forecast mentions some possibility of winds of up to 60 knots for a time and waves up to 7 meters.

If any of yours are sailing the stretch right now, consider sending them a heads-up. Better prepared than sorry.

Meanwhile on the E side of the Atlantic the weather is mellow and the coast from Gibraltar towards Cabo Verde is mostly windless.

Sources:

Radiofax: NOAA.
Grib: NOAA.
Graphics: zyGrib.

Cheers,
b.

[barnakiel]

April 14.

This animation is based on last night's gribs.

You can see how far South a low pressure cell can stray in absence of a blocking High. Areas to below 30N are forecast to be affected.

You can also observe how the system 'lingers' at 30N indecisively. This is a full 48hrs gale for some boats, maybe more. This is also headwinds for those going the top route at 40N.

In the second part of the animation you can see how a system that is forecast in the 96hrs horizon may join the earlier one and the two revolving later around a common center. Quite a view.

I hope this animates. If it does not, go get windyty or some other viewer and watch it there.

Cheers,
b.

[barnakiel]

Possibly CF does not support animated gif files.

I am attaching a video version of the above. Hope this plays clean. Possibly you must click on it.

PS Tested in IE - works fine.

Cheers,
b.

[barnakiel]

April 18.

A gale right bang on the direct route from West Indies to the Azores, to be followed by another similar one around Saturday.

Plenty of headwinds on the Bermuda - Azores route - esp. for those close to the Azores.

Cheers,
b.

[MarkJ]

Yes, I was thinking about those wafting round that one. Nasty.

NHC gives it 30% chance if becoming a TC.

[barnakiel]

April 21 / 22 (past midnight UTC)

Today just a quick dump of present NOAA chartlets.

I think what is interesting is not that there is a second system nearly where the earlier gale/storm were but possibly even more the intensity and forecast track of the system in the 96hrs forecast. A punch into the soft underbelly part of the routes.

Not a place to be now in a small boat.

Cheers,
b.

[Palarran]

Thank's for doing this Barnacle. I wish I could read synoptic charts half as well as you but when I look at them the detail doesn't seem easy to understand, or how to use it to predict the future.

I bought the subscription to Predict Wind. When I run the model right now, using polars for a Lagoon 500, it shows a pretty quick and safe crossing. Of course we would download and run the data daily, but based on the four weather models it uses, we would probably leave now.

It would be interesting to me to track an imaginary boat leaving at a certain time and see how the weather develops as the crossing progresses.

[Palarran]

I took snips of the model maps for 6 days. That is probably too far out to get an accurate prediction of the weather but this is what Predict Wind is showing. Also, with my program, it has the boat motoring at 6 knots if the wind is below 10 knots. I don't know if that would be accurate depending on if we were reaching or running. It doesn't have the ability to differentiate the two.

[barnakiel]

I would propose that (?) there is no way any software can give you anything like even marginally reliable routing beyond X days' horizon(?). Not even in a boat as big and fast as a Lagoon 500, I believe. We can attempt to establish what the above X is.

However, the exercise you want is easy to do with any wx routing package, you can do the following, e.g.:

DAY ONE: set the points and pick up the polar, DERATE according to how the boat is sailed/loaded/equipped, DERATE according to the sea-state, download the grib, run the model, check if you agree, if you do: MARK DAY ONE END POINT.

DAY TWO: use the marked above waypoint as your boat position, repeat the whole exercise (download fresh gribs, etc).

Do the above, say daily, and you get to see a what it would be like in real life. It takes about two or three weeks of daily (or any other period) attention.

The above routine will work as if you have sailed an actual passage. But it must be done on a regular daily or other periodical basis - for you can download the gribs daily and run the exercise at a future point - only if you are very keen on manipulating the routing software. And not all software allows you to manipulate this much either.

On reading the weatherfax chartlets: It is indeed a very very easy thing. The air around the Low and High cells moves in its distinct manner - direction and speed related to center, etc. The other visible features are fronts and on a front there is a specific set of wx features too - typical cloud formations, wind shifts, sea state conditions. So this is like a general plan telling you the train is coming and what kind of train it is. The grib data interpreted by any software will tell you then how fast the train is moving and also at what angle it will hit you.

It takes not more than a week of intensive study to be quite literate with interpreting a weather fax image. And it is best done while you are there - so that you can see the features shown in the wxfax as they pass around you - the change in air clarity, the change in cloud formations, the wind shifts, the lightening and the wind turn on the ridge and the acceleration and the wind shift on the front. Etc.

Wxfax images are a great tool to predict the best days to watch out for a green flash when you are in the Caribbean - for you want to know when the pre-front clearing comes. A grib file will not tell you this. But looking at the horizon every morning will. The beauty of using various sources and seeing what they actually attempt, and can/cannot, describe.

Can you possibly let me know what passage time your software generated for your boat? I am surprised you got full passage covered as my longest gribs show 10 days data and beyond 4 days I no longer use this data for any planning. But even with the max 10 days' grib data, vastly unreliable as it is, I do not think my packages (MaxSea and qtVlm) could predict a Lagoon 500 getting from the West Indies to the Azores.

Choice of departure time and timing is dependent on how strong the boat and crew are: North Atlantic speed records are often attempted at times when no cruising boat should leave the harbour. The rest is choices of the skippers who are ultimately responsible for safety of their crews.

Cheers,
b.

[MarkJ]

Originally Posted by Palarran

Also, with my program, it has the boat motoring at 6 knots if the wind is below 10 knots.

Can you adjust that to under 8 knots motoring at 4 knots? That gives you some fuel range.

[Palarran]

Originally Posted by MarkJ

Can you adjust that to under 8 knots motoring at 4 knots? That gives you some fuel range.

Yes, you can adjust it to whatever you want those two parameters to be. For my specific boat, in calm seas doing 1800 rpm we achieve about 6 knots, so that is what I set it for. I have over a 1000 nm range using this parameter.