Berkeley Sensor Accuracy??

[johnl]

Well after missing the great wind on Monday due to work (need to work on this work thing ) I managed to make it out to Berkeley yesterday (Tuesday). This was my first sesson at Berkeley this season (but not my first session for the year).

Sensor was showing an average of 20. When I got there riders were coming off the water on 5.2 - 5.4 sails and many were slogging in saying it had dropped off (around 4pm) I ended up rigging a 5.7/95l combo which is my bay area light wind rig (most others were on 6.2's). I managed to sail for almost an hour before it dropped off more but it was marginal for most of the session.

When I got home I looked at the sensor and saw that from 3:30 pm till 5pm (the time period I was there) the average was right at 20. 20 for me is normally 5.2 with plenty of wind.

So I guess I have two questions.

1. Have most of you found the Berkeley sensor accurate this year? Or reading high like last year.

2. Looking at the graph it shows the average of 20, gusts of 21 or 22 with lulls of 15. On the water it was more like the lulls. But with lulls that low (which were more common than the gusts) how does the sensor manage to show an average of 20?

[kevinkan]

The Berkeley sensor definitely reads high. I would say it is off by 3-4 mph or so. Five years ago, a reading of 22 meant powered 4.7 and small board for me... now it seems like 5.2 and 90-100l. 16 used to mean 5.7 and 100l and fun... now it means slogging... i don't think i got that much heavier! A reading of 28 used to be getting my nuts blown off... now it's just a windy day where I contemplate whether to rig small or go w/ 4.7 (like Monday). I know it's hard to tell what is actually the true windspeed on the water when the sensors are on top of buildings and whatnot, but the Berkeley sensor seems to be way more "off" than others.

There was some discussion two years ago about recalibrating or adjusting the output from the sensor... I would vote for this. Anybody else?

[madspaniard]

Agree with Kev, but if I recall well the iwindsurf staff said that they could not do much about it. I think they need to look into it since a lot of people sail this spot and the two clubs in the marina are bringing more people to the water.

Do you also feel that the sensor reads lower with North winds? It seems like it usually happens with the westerlies.

[sailandbail]

Isn't the sensor on top of HS Birdshits right by the launch? It seems like the building makes a nasty eddy there that might mess with the reading (depending on direction). There is another online meter at ocscsailing.com to double check the reading.

[merde]

Are you guys talking about the OCSC sailing club sensor?
or is the one from Iwindsurf different?

Strange, because then OCSC sensor reads high this season too.
Somehow i think because the sensor is way up a building it catches the wind better. like a god damn kite...

Monday was great indeed, i launched from Point Emery, with a 4.7 and 65l

[victor]

i don't even go to berkeley unless it's reading over 22 and rising.

i launch at his lordships and the wind in the parking lot seems a lot stronger than it is on the water. there must be some conditions that make the wind stronger where the sensor is situated.

the tell tale is if the birds can stand on the roof of the restaraunt then it's not windy enough.

it also likes to die of very quickly without any warning.

[johnl]

I also launch as HS Lorships. I know because of the jetty and the building for some reason it cases some strange wind eddies right at the lauch. But after a short walk/swim you get to launch right in the wind. Now if the sensor is in fact on top of this building, that could be the cause.

I tend to sail on SW and W wind at Berkeley so I can't speak about northerlies.

I thought the IWindurf sensor (the one I was talking about) is at the UC building. But I don't have verification of this.

But it is nice to know that at least it is still consistantly high. I was there last year when it read 19 and it were no caps on the water. I don't even think my 7.5 would have worked. Figure that one out....

[johnl]

Oh yeah, as far as the OC sailing club's meter, you have to be a member to access that

[veterduet]

I asked Mike Godsey about the sensor. Here is his "long winded" but as usual thoughtful reply:

About the Berkeley sensor. In the summer when there is a deep cool (ie heavy) marine layer the wind is very stratified with the wind at the surface slowed by friction and the wind even 20-30 feet above being stronger since there is less friction especially at Berkeley where there is only water upwind. But in this pattern where there is lots of turbulence and and the wind is moving up and down a lot the effect of friction is weaker so the wind at the surface and at the sensor is much the same. Bottom line, expect the sensor to over read in the summer.

[magwire]

The windtalker phone number for Berkeley that SFBA (510)843-3446 used to maintain was way more accurate.
Not sure where the sensor was located but it was much better than iwindsurf's.
SFBA's board decided last year to eliminate the windtalker without asking the members because they claimed,"No one used it."