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Old 09-07-2014, 08:27   #1
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Gribs constantly wrong now I'm in the Med.

Hello all,

Loving the Med thus far! However I've noticed the forecasts (I mostly use gribs) are WAY out most of the time.

I've just had two weeks of trying to dock in 20-25 knot winds any time between 12-4 isn when the gribs are telling me it'll be 5-10.

While my experience of docking in higher speed winds has improved no end I'd sure like to know what the deal is with weather forecasts being so out around these (new to me) parts.

Is it just a lack of my knowledge of this area (I'm just about to head over to Ibiza from Southern Spain) or are there things I'm missing?

Any help with better forecasting methods over gribs would be most welcomed also.

I've looking at a few over the last 2 weeks and all of them got it pretty much wrong every day.

All the best,
Simon
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Old 09-07-2014, 08:35   #2
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Re: Gribs constantly wrong now I'm in the Med.

gribs and the computer wind models can help you pick meltemi (Greek/Turkish area's) and other systemic wind patterns. However, they can't really help with local winds, orographic winds (channelling between islands, high mountains causing 'bullets' of wind) or local thunderstorms. These are best picked by observation.

Regarding meltemi winds, I usually add 10 knots to forecast maximums, and that turns out usually right!

Having a longer keeled boat, I've really appreciated all the extra practice I've gained in high winds!! However, I've also learnt a whole new variety of ways to get the boat in safely in high winds.

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Old 09-07-2014, 08:48   #3
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Re: Gribs constantly wrong now I'm in the Med.

Thanks Steve,

Yes this is what I've found also, a good 10 knots on top.
Just makes it hard to plan passages I'm finding. You really don't know what you're going to get until you're out there which is a worry to me.
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Old 09-07-2014, 09:19   #4
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Re: Gribs constantly wrong now I'm in the Med.

Hi, Simon, and welcome to the Med!

The weather there is so much influenced by the land masses around it that forecasting is simply next to impossible. While sailing there we checked the forecast twice a day, and we still got hit with shitty weather. Guess why we enjoy the Atlantic so much???

The good thing is that in most areas you can stay at anchor a few more days if the wind picks up; most of the really nasty ones (Mistral, Tramontane, Bora) blow from land to sea...

Oliver
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Old 09-07-2014, 09:20   #5
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Re: Gribs constantly wrong now I'm in the Med.

Go to: Mediterranean Marine Weather Services / Franks-Weather | The Weather Window

We found the local vhf forecasts to be pretty accurate in Greece and Turkey. Franks site is a great resource for European weather.

Enjoy.
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Old 09-07-2014, 14:13   #6
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Re: Gribs constantly wrong now I'm in the Med.

Navtex is a great resource, relied on it a lot in the Med


dave
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Old 09-07-2014, 14:23   #7
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Re: Gribs constantly wrong now I'm in the Med.

If your gribs tell you that the Mistral is blowing into the Golfe de Leon, have a rest. Go visit Sagrada Familia, enjoy a walk along Los Ramblas. Welcome to the Med, where often there is too much wind or none at all.
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Old 09-07-2014, 14:31   #8
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Re: Gribs constantly wrong now I'm in the Med.

If you can get a forecast that has a local meteorologist giving personal input, like Aladin here in Croatia, you do get improved accuracy. I try and keep studying the big weather systems, and understanding what is happening and why - like trying to understand the weather around Genoa. Fascinating stuff. Franks weather has some great links and info.
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Old 09-07-2014, 14:54   #9
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Re: Gribs constantly wrong now I'm in the Med.

Quote:
Originally Posted by steve.garlick View Post
gribs and the computer wind models can help you pick meltemi (Greek/Turkish area's) and other systemic wind patterns. However, they can't really help with local winds, orographic winds (channelling between islands, high mountains causing 'bullets' of wind) or local thunderstorms. These are best picked by observation.
That a true statement for the Sea of Cortez, MX also where the grib files can be close to useless near land and spot on out in the middle of the SOC.
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Old 09-07-2014, 16:47   #10
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Re: Gribs constantly wrong now I'm in the Med.

IMO, gribs are good for indications of synoptic flow at sea, and more or less irrelevant for the land-sea interface, where we anchor. S'okay. Out here in Australian the wind forecast strengths are based on 10 minute averages, and they tell you, "Gusts may be up to 40% stronger than the averages given here." Perhaps that would work as a conceptual guidline in the Med as well????

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Old 10-07-2014, 00:02   #11
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Re: Gribs constantly wrong now I'm in the Med.

I use windfinder and it's been pretty accurate. My first year when I was in the same area you are, I tried gribs and they where usually the opposite of the true weather.
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Old 10-07-2014, 03:31   #12
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Re: Gribs constantly wrong now I'm in the Med.

Thanks for all the replies. As normal some amazing advice I'll work through.
I'm just happy it wasn't just me having issues with the Gribs.
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Old 10-07-2014, 09:42   #13
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Re: Gribs constantly wrong now I'm in the Med.

You are tied to a dock so obviously near shore. Most models (like GFS) do a poor job near shore. Some models are now being developed specifically to improve near shore forecasts. For example, COAMPS.

I suggest you download GRIB data from COMAPS for a few days and see how it does for your area. It is more accurate here in near coastal Panama than GFS.

Also remember that GRIB data is raw model output without the benefit of professional review. You should also download Weather FAX forecasts for your area and see how they compare.
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Old 10-07-2014, 09:55   #14
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Re: Gribs constantly wrong now I'm in the Med.

Quote:
Originally Posted by simonpickard View Post
Thanks for all the replies. As normal some amazing advice I'll work through.
I'm just happy it wasn't just me having issues with the Gribs.
Note that GRIBs are not actually a forecast, but just a format for storing forecast data. Saying GRIBs give bad forecasts is a bit like saying JPEG files take bad pictures. It all depends on the model you download data from and some models are better at some things than others. Its not uncommon for models to disagree too. Comparing them can be useful in making your own decisions about weather (this is what the pros do). For example, I usually download from both COAMPS and GFS and compare. If they agree then that gives me a high degree of confidence in the forecast. If they disagree then I need to do some more digging.

All the services like Predict Wind, Wind Guru, etc...get their base data from these same forecast models. It costs huge dollars to develop and run forecast models, no way the small companies providing these services could afford it, they just know how to choose/massage/present model data better than the average cruiser.
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Old 10-07-2014, 11:40   #15
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Re: Gribs constantly wrong now I'm in the Med.

Models that do not allow for land masses will not give you good gribs for the Med. Remember each mass creates its own air movements. When the coastline is intricate or complex, or when there are very many islands around, local conditions may get complicated to the point where no forecast will be good.

But local knowledge may help. You normally will develop some of it after a couple of sailing weeks spent in the same region.

b.
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