Wind Forecast Confusion

WNDZRFR · Posted: Mon Apr 20, 2015 2:07 pm Post subject: Wind Forecast Confusion

Looking at today's forecast for say Berkeley the write up states "Berkeley reaching upper teens." But then in the hourly chart it is written "18-22" from 3-5pm. The difference in 19 to 22kts is a major difference (in my case 2 sail sizes and 1 board size). Since both forecasts are made by the same person why is there this discrepancy? This happens quite often and I don't know which numbers to go by. Please help those lost in forecast land:)

Professional Meteorologist Forecast
San Francisco forecast valid for Mon, Apr 20 2015

East and North Bay: Berkeley reaching upper teens.

Berkeley 6A-7A-8A 9A-10A-11A 12P-1P-2P 3P-4P-5P 6P-7P-8P
Speed (kts) 6 - 10 8 - 12 13 - 17 18 - 22 14 - 18
Direction WSW WSW WSW WSW WSW

windfind · Joined: 18 Mar 1997 Posts: 1902

Hi Alien51,

I was not forecasting yesterday but I probably have made the mistake you describe as often as any of the other forecasters.

After an hour or two of working up a forecast we write up the text wind ranges. Then we have to enter all the directions, high and low wind data in the tables. That means about 195 separate data entries.

To save some time the model data is auto entered so the forecaster is not starting from scratch. While entering most of the data by hand it is easy to lose track and leave some of the model data in the tables. And sometimes the model data is way off compared to the human forecast.

Comparing the 195 table data entries to the text forecast is time consuming and error prone

So if you ever see a major discrepancy between the text wind range and the table data go with the text forecast since it is much easier for us to proofread.

Mike Godsey
iwindsurf.com

WNDZRFR · Posted: Mon Apr 20, 2015 3:06 pm Post subject:

Thanks for the clarification Mike.

I've always wondered how you guys keep ALL the forecasts straight for the entire US twice a day!

I'll go with the write ups.

windsrf · Joined: 01 May 1998 Posts: 464

Interesting!

& Good to know.

LeeD · Joined: 12 Jun 2008 Posts: 1175

I suspect Berkeley is one of the hardest sites to predict wind.
A few degrees towards the SW, the wind can go over to Pt. Isabelle.
A few degrees westerly, and most everyone is fighting to stay upwind, even with readings of 18-24 mph, and using 6.5 sized sails.
And big outgoing tides, usually forgetaboutit.... just huge lulls in the wind, usually dropping, then coming up unexpectantly.
And NW ocean winds, clear days, a window of 2-3:30 might be the total for the day, especially if ocean NW winds are stronger than 28 at Bodega Buoy.
That's why Sunday was such a blessing. Solid 19-25 mph breezes, little change in direction, and chop not nearly as crazy as Friday or Sat., which had equal winds early, and died off very early.