2016 Weather to the Azores

[Dulcesuenos]

So far looks like a motorboat ride to Bermuda

Sent from my PLT1077G using Cruisers Sailing Forum mobile app

[barnakiel]

Here a middle of the road story of how weather forecast probabilities are set and read:

https://www.minitab.com/en-us/Publis...ble-Are-They-/

It is a bit 'scientific' but not behind an average joe set of cognitive skills ;-)

For the rest of us: e.g. wind force:

(very VERY broad rule, not a scientific one, only an approximation)

Expect:
tomorrow - wind within say .80 to 1.20 of the forecast,
each next day - lower limit .8 x .8 of the forecast, upper limit 1.2 x 1.2 of the forecast.

! Less accuracy if we are sailing in the mid latitudes!

Expect:
tomorrow - system positions within circle radius X
each next day - system positions within circle radius derived from area of circle X multiplied by a factor.

etc

The above is very simplified but gives three essential hints:

- watch the weather DAILY,
- ALLOW FOR 'unexpected' weather conditions,
- EXPECT wx in say 4 day to differ from today's 96hrs forecast.

The difference off becoming smaller each day as the forecast rolls over and your 96 hrs forecast is 'now' 72 hours ahead and so on.

Also: mind the fact that there are very few weather sensors over the oceans and so plenty of what you see in visual and digital wx feeds are computer and human, educated, guesses derived mostly from satellite images and measurements.

Later some chartlets as usual.

b.

[barnakiel]

Very bad connection here and so my 3rd ? try today.

April 26 update:

- The analysis sheet looks fine with heaps of a High system of not all that high pressure. Still, nice to see it.

- The 96hrs frcst sheet looks very nice with one 1027 and two minor systems on the good side of the force an one very lost, very lonesome one on the dark side - it looks very lost and very hesitant and you do not want it to be there when you are crossing. I hope you are not.

Cheers,
b.

[barnakiel]

28 April 96hrs frcst

An early bird. We will see how long it fares. They give names to Lows maybe us sailors should be giving them to Highs?

I name this one "Cheater". We will see how much of a seer I am ;-)

Cheers,
b.

[monte]

Thanks Nick. Great to read your synopsis. I've been noticing the fairly long range gribs to be quite accurate around the Caribbean and Atlantic. Much more so than the Med.

[poiu]

Originally Posted by monte

Thanks Nick. Great to read your synopsis. I've been noticing the fairly long range gribs to be quite accurate around the Caribbean and Atlantic. Much more so than the Med.

Accuracy depends hugely on where you are, the season and the type of weather being predicted.

In northern Europe, in winter and to an extent in summer too, in a predominantly low pressure environment with lots of lows and fronts around the 96 hr forecast is a complete fantasy fairy tale, but it will usually be right 100% in that the weather is going to be not so nice for one reason or another. In summer particularly in a predominantly high pressure area it will usually be bang on.

In the Caribbean I find the weather predictions are often good too. In winter the 96 hr forecast is pretty good. So good I look at it for a few seconds only every few days. In the hurricane season it's different.

I remember the funny scenes in Steve Martin's L.A. Story about the weather. Makes the point well. Couldn't find a link on YouTube though.

[boatman61]

They may be a tad better Monte.. however I'm more concerned by the trend to Easterlies running so high North.. could we be approaching a wind reversal period.. where Easterlies become the predominant wind in the N Atlantic.??
5 weeks to my St Martin departure...

[barnakiel]

Originally Posted by monte

(...) I've been noticing the fairly long range gribs to be quite accurate around the Caribbean and Atlantic. Much more so than the Med.

Caribbean wx 'comes' from the ocean side - huge and flat areas of uniform surface with minor only instabilities induced by cloud patches and moderately only varied water temperatures. Hence not only greater stability of the weather but also better predictability of mathematical models that end up with what we get in the grib files.

On the contrary, Med weather comes from a mixed surface(-s) of land and sea, with ranges of tall mountains, deserts, forests, etc. all of which accepting, reflecting and radiating sun energy at vastly different rates. This is what drives the apparent instability - so many more factors there. And mathematical models are not at all very good at delivering high probability predictions from multivariate analysis. (More variation and/or lower R squared, for the mathematically inclined).

Wx towards the Azores is an in betwix mix of the more stable ocean weather and a continuous onflow of ex-continental systems rolling from N America towards N Europe on top of (hopefully present) Azores high. When the High sets in, most of continental instability get deflected way up North - we get less wind to sail on but we also benefit from fewer Lows and fronts to wipe out the fleet. This is exactly the risk with setting off early: the High may either not be there or too weak and so one is sailing in what can be seen basically as US/Canadian continental weather rolling on towards the E. It must be noted that Lows can develop higher wind speeds over flat areas where there is less surface friction. They can be also fed by higher humidity, etc. This is an adventure for big boats only with competent and strong crews.

When you use gribs to supplement your wx diet - do try to load up more than one model each time and compare the results - you will not only find differences but also learn over time to select one of the models over the others for any specific wx situation. BTW There is quite a lot new happening in this field and we can expect major improvements over next 5 to 10 years.

Have a fine sunny day out there,
b.

[barnakiel]

Originally Posted by boatman61

(...)

5 weeks to my St Martin departure...

Lucky duck!

b.

[monte]

Phil I think it has a lot to do with waiting for the Azores High to settle in place which should be around about your departure time, fingers crossed. Once it settles we will have the Portuguese trades and more predictable weather in the vicinity. Obviously you know this already

[barnakiel]

Originally Posted by monte

Phil I think it has a lot to do with waiting for the Azores High to settle in place which should be around about your departure time, fingers crossed. Once it settles we will have the Portuguese trades and more predictable weather in the vicinity. Obviously you know this already

And what when it does not?

I used a question mark at the end of the statement which those who know me immediately recognize. I am actually asking a question which implies I do not have the answer.

As I have received more than one msg telling me I am dense (as if I ever claimed to be everything to everybody) I think this is a fine koan for all those who wait for the weather to become what they see as the minimum optimum to take off.

How should the 'the Caribbean to the Azores' be sailed in absence of the Azores High?

Cheers,
b.

[barnakiel]

Cheater visible now in long gribs. Forecast to place itself to the W of the islands.

This is a good sign, I think, as at times such early systems may pop up mid-April or afterwards only.

The situation over the continent looks promising too.

On the E side from Gibraltar towards the Canaries the wx in typical pattern with a gale from the Gibraltar likely.

b.

[Dulcesuenos]

What's your thoughts concerning FL to Bermuda next week say Tuesday?

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[barnakiel]

End of month, the month of April.

Our lost Low friend is still there, mostly dissipating but it takes time. There is a High to the NE of the Azores, way too far, but it has good pressure in it. Forecast to drift even further our E/NE soon.

96hrs frcst shows a new High 1025 to possibly roll in from the W then a front and THEN another High 1022 dissipating on the edge of the continent. Dissipating OK but I think it is good to see the continent picking up some pressure. This would be our spring / summer pattern. We do want to see some High rolling over from the continent.

The last image is a long term GFS grib based graphical slider at 5 May 1200UTC. Not to be used for navigation. Still, nice to look at.

Yesterday learning about RTTY (which I have never used this far, have you?) I came across an interesting piece of software that I believe is worth mentioning to other sailors who may be interested in making their own wx guesses. It is called Digital Atmosphere and I post a link below. I am not related to the company. I will try to find time and test it (demo package is a freebie):

Digital Atmosphere - Weather Graphics

Should the link be removed for commercial reasons, I will ask the moderators to leave the a/m name of the package for other wx freaks to do their own google search.

Cheers,
b.

[boatman61]

Originally Posted by monte

Phil I think it has a lot to do with waiting for the Azores High to settle in place which should be around about your departure time, fingers crossed. Once it settles we will have the Portuguese trades and more predictable weather in the vicinity. Obviously you know this already

Seems pretty late to me this year.. had better weather on my Feb 2014 trip to the Azores..
I've gotten used to the Easterlies being around 22-23N maximum this time of year.. still.. makes life less boring..