How accurate is NOAA, really?

[science abuse]

So I've been watching their forecasting "tool" for a bit, and its eems like the kind of "round up", biasing the more dangerous side of their margin of error.

Those of you who have been at this a while; how accurate does NOAA tend to be in their forcats?

I've got a sailing trip that begins tomorrow, and they're calling for light variables. What are the chances that they'll be wrong in a way that helps me?

[jehardiman]

Depends on where you are starting from. Is this marine (offshore) or onshore. For onshore forcasts, look at a front map or the wind prediction. No fronts then generaly light winds and tomorrow will be just like today, but remember onshore winds are more effected by surface terrain than offshore. Try this NOAA site.

http://www.weather.gov/outlook_tab.php
or this one
http://www.weather.gov/forecasts/gra...lement=WindSpd

[science abuse]

Good resources, thanks for the links.
This is what I've been using: http://www.glerl.noaa.gov/res/glcfs/

[CatBuilder]

Mostly, I find the "round up" to be true as well, since their forecasts tend to be for maximum expected winds.

I find them to be quite accurate though, once you have spent enough time looking at various NOAA pages, then actually getting out on the water.

It's all about seeing the general patterns, rather than a snapshot of, say, 3PM, even though they do set up their forecasts with times such as 3PM. The NOAA information is just a guideline, IMO. You use it to figure out what is most likely to happen. Anything and everything can change the local conditions though - for instance - a set of mountains or hills funneling wind down to the sea when you are just offshore can take a moderate breeze and make it into a wind tunnel area where you have to reef or at least ease a sheet.

It's best to use NOAA as a general idea (small craft warning is usually accurate, as are 5-10MPH wind days). Then, get used to the area you are sailing in and get a feel for the weather. Read the clouds. Know if the wind kicks up every evening as an onshore breeze. Watch the water and see gusts of wind coming.

It's far more accurate to observe your local conditions yourself than to rely on a wide swath of a NOAA zone for your immediate weather.

[science abuse]

Originally Posted by CatBuilder

It's far more accurate to observe your local conditions yourself than to rely on a wide swath of a NOAA zone for your immediate weather.

Couldn't agree more, unfortunately I'm at their mercy this time; I don't live anywhere near where I'm going.

[science abuse]

After this weekend, it appears the best solution is not bother checking the weather before your trip. Just ask the Harbormaster when you get there. He'll tell you someting different than the forecasting tools, and he'll be right.

[hoytedow]

If you are not checking the weather, please name me in your will before you go.

[science abuse]

Originally Posted by hoytedow

If you are not checking the weather, please name me in your will before you go.

I'll be sure to go into huge debt on a nice boat before I do.

[jehardiman]

Originally Posted by science abuse

After this weekend, it appears the best solution is not bother checking the weather before your trip. Just ask the Harbormaster when you get there. He'll tell you someting different than the forecasting tools, and he'll be right.

Climate is what you expect, weather is what you get...And if you don't like the weather; wait 5 minutes.

No forecast is ever correct, just like calling ahead doesn't work that well either.

[Poida]

What you need is weather forecasting like we have in Western Australia.
Typical Forecast:

Fine with a chance of a shower.

Winds 10 - 20 knots with possible gusts to 50 knots
East to South East swing West to South West to West during the day.

Temperatures Mid Twentys to Thirtys

They are seldom wrong!

[Quatsino Boater]

I don't know if this helps, but I have a barometer on board my boat. i found this chart somewhere , I still can't rember where though. here goes:

Barametric change in pressure

1mb/hr----- strong wind force 6 to 7 -----22-33 knots
2mb/hr----- gale force 8 to 9-----34-47 knots
3mb/hr----- storm force 10to 11-----48-63 knots
4mb/hr-----hurricane force 12 ------> 64 knots
5mb/hr----- weather bomb

So typically here the sea state is around 1 to 2 meters on any given day. I check the barometer every 45 to 60 min to see a trend. Usually around 1 pm local the wind will pick up fast and the sea state will go to capping 2 to 3 meters. I have a planing boat at the moment with a 20 + mile run back to my marina so I can get into our inlet and get out of a large fetch so choppy 1 meter will be the worst of it.

I like the fact that I am getting local barametric readings around my boat and not some fixed location that can be far away and drastically different conditions.

i hope this might help

[michael pierzga]

Met office or Noaa forecasts for oceanic sailing are very accurate. Inshore in areas with many geographic influences ineveitably cause discrepancies in computer models. For inshore work local forecasts are best.

[powerabout]

where do they get the data for offshore?

Re barometer here close to the equator...they never work because the needles have all seized up

[jehardiman]

Originally Posted by powerabout

where do they get the data for offshore?

Re barometer here close to the equator...they never work because the needles have all seized up

There is a whole range of data buoys, and then there are the ship reports, NAVMET flights, the EOS satellites with SAR, etc.

Go here for the tip of the iceberg...

http://www.ndbc.noaa.gov/

[powerabout]

nice link , thanks
a bit thin in Indian ocean and around Asia
I have been using the NOAA Gribs and wondered where the data comes from as they show many small pressure patterns and hence winds
Maybe its commercial ship reporting data out here?