Predicting the Wind

Windsurfers and Kitesurfers get a little bit obsessed with the wind. Of particular interest to me is being able to predict conditions a few days out so I can make arrangements with work or family to get out on the water.

Windfinder good weekend

There is nothing worse than having a Windfinder prediction that looks as good as this...

Windfinder poor weekend

...turn into something as poor as this. Fortunately this sort of thing mostly happens in winter, but it still makes everyone a little bit crazy.

Managing Expectations

Certainly we can't change the wind conditions where we live, but we can study the historical record and change our strategy throughout the year to make most of the expected and prevailing conditions. For this article I downloaded and prepared graphs of climate statistics for Bundaberg Airport from the Australian Bureau of Meteorology website.

To start with we can take a look at the historical average monthly wind speeds for Bundaberg Airport. The red line is the recent average. The good news is that average wind speeds seem to have increased marginally.

9am Monthly Averages

Winds in the morning tend to be lighter than those in the afternoon.

9am Average

3pm Monthly Averages

Given that most of us work during the day, afternoon sessions are the most convenient, so this article focuses on afternoon wind statistics.

3pm Average

Wind Roses

Each wind rose uses the following scale to represent different wind strengths. They go up in increments of 10 km/h. The bit we are interested is everything above 30 km/h which is above 15 knots - ideal planing conditions.

Wind Rose Legend

Wind rose legend

A typical session

A typical session

Given that on a typical day, the wind picks up after 10am and drops off after 5pm, each 15+ knot session lasts about eight hours tops. This gives us a formula for converting the percentage of wind in the wind rose to the expected number of sessions per month.

S = N ÷ (P × 3)

Where P is the wind rose percentage above 30 km/h, N is the number of days in the month and S is the expected number of sessions per month.

9am Annual Wind Rose

Morning winds tend to be dominated by southerly and south-easterly wind directions.

9am Annual Wind Rose

3pm Annual Wind Rose

Afternoon winds tend to be dominated by easterlys, but you really have to examine each month (below) to get a feel for what is actually going on throughout the year.

3pm Annual Wind Rose


South-easterly Dominated Wind Patterns

From January to May, the dominant wind direction shifts from easterly to south-easterly. This is our best time of year, but you should only expect about 34 days of easterly to south-easterly sessions during this period.

Elliot Heads

Elliott Heads

The Elliott Heads is our favourite launch site for south-easterly (RED) sessions. You can blast the flat water in the channel, waves out front or off Coonarr. When the wind turns easterly (BLUE), and the tide is high, you can do short runs to Dr May's Island or off Coonarr. At low tide you can still sail off the beach out the front. When the wind turns north-easterly (GREEN) it is a bit more difficult. The channel in front of Dr May's Island has a wind shadow, but once you get out from behind it the wind is quite good, but only at high tide because there are sandbars at the end. The channel off Coonarr has deepened, so it may be OK at lower tides, although getting there and back is a bit of a hike in a north-easterly.

Bargara Boat Ramp

Bargara Boat Ramp was once a favoured launch for south-easterly wave sessions, but after some misadventures and damaged boards it has fallen out of favor.

January

January is dominated by south-easterly and easterlys, with 8% above 15 knots.

3pm January

Expect about 7 days of south-easterly to easterly sessions in January.

February

February is dominated by south-easterly and easterlys, with 7% above 15 knots.

3pm February

Expect about 6 days of south-easterly to easterly sessions in February.

March

March is probably our best month. March is dominated by south-easterlys and easterlys, with 10% above 15 knots.

3pm March

Expect about 9 days of south-easterly to easterly sessions in March, with a few truly epic sessions!

April

April is dominated by south-easterlys, with 9% above 15 knots.

3pm April

Expect about 8 days of easterly to southterly sessions in April.

May

In May the number of sessions really starts to drop off, with only 4% in the easterly and south-easterly direction above 15 knots.

3pm May

Expect about 4 days of easterly to south-easterly sessions in May.


No Dominant Wind Pattern

June and July are probably our worst two months because the average wind direction is all over the place. There are only a few south-easterly sessions to be had and the wind direction can shift even during sessions, making everything difficult.

Kelly's Beach

Kelly's beach was a favourite launch for Jason last year during this period. It offers several convenient car parks and a large sandy beach for mostly hazard free egress - just watch out for the rocks under the sand. It is a pretty flexible site, supporting all dominant wind directions, and the Bureau models always report Bargara being a few knots stronger than Elliott Heads, which could make all the difference in winter. It is also patrolled by life guards, which might also be handy in winter, if you got into trouble getting back in because the wind died.

June

June sees the beginning of a shift to this winter wind pattern. There is no dominant wind direction, with only about 4% above 15 knots.

3pm June

Expect about 4 days of strong winds, but only half will have favourable directions.

July

July is probably the worst month. There is no dominant wind direction, with only 3% above 15 knots.

3pm July

Don't expect much in July. Short sessions and lots of off shore winds.


North-easterly Dominated Wind Patterns

In the later part of the year, the dominant wind direction shifts to the north, and the wind strength picks up again. Launch sites with an unobstructed northern aspect are preferable to avoid wind shadows and turbulence. Expect about 32 days of northerly, easterly and south-easterly sessions from August to December.

Burnett Heads Marina

For a true northerly winds at high tide, the Burnett Heads marina is a perfect spot for kitesurfing, and there is a channel down the centre that windsurfs can use, but if the wind dies, slogging back though the mud is a bit hairy.

Nielsen Park Beach

Nielson Park beach is also another potentially good launch for northerly winds because the approaching wind travels over the water, however the rock groin is a potential hazard.

August

August sees the beginning shift to a from the winter pattern to a more northerly pattern. August winds are still all over the place, with only about 4% above 15 knots.

3pm August

Expect about 4 days of north to south-easterly sessions in August.

September

September is dominated by northerly, easterly and south-easterlys, with 7% above 15 knots.

3pm September

Expect about 6 days of north to south-easterly sessions in September.

October

October is dominated by northerly, easterly and south-easterlys, with 8% above 15 knots.

3pm October

Expect about 7 days of north to south-easterly sessions in October.

November

November is dominated by northerly, easterly and south-easterlys, with 9% above 15 knots.

3pm November

Expect about 8 days of north to south-easterly sessions in November.

December

December is dominated by northerly, easterly and south-easterlys, with 8% above 15 knots.

3pm December

Expect about 7 days of north to south-easterly sessions in December.

Conclusion

It is interesting to see how the dominant wind patterns shift over the year. While I think it is constructive to plan for the direction that the wind is most likely to come from and choose an appropriate launch site, the main thing I have taken away from this analysis is that good sessions are a rare and precious thing. There are only about 65 days of 15+ knot sessions a year. That's an only an average of about one session a week. Sometimes they come in three to four day sets, while at other times just one good afternoon here and there. Clearly you have to be able to get out on the water when ever the wind is blowing, even if its just for an hour in the later afternoon, or risk missing out. No point having all your free time when its calm. It can be a real challenge finding the right work/life/windsurfing balance.

Posted by Henry Thomas, 6 years ago on Thursday, April 14, 2011

2 comments:

Mat Watkins said...

This has been a really hlpful article, however I am confused about kitesurfing in the marina has anybody actually done this and where is the launch site. Thanks again for the informative material henry.

Posted 6 years ago on Thursday, June 9, 2011

Henry Thomas said...

I have not had a session there yet, but Andrew and Al had a few sessions in the marina last winter. From what they told me the key issue is the tide - you have to be there an hour before high tide, and the wind needs to be northerly (NE, N or NW). For kites, the shallow water isn't as big an issue, but for us windsurfers with long fins it is - so we need to launch at the boat ramp, or for a North-westerly where the astrix is. My recollection is that Al launched over in the South east corner somewhere.

Posted 6 years ago on Thursday, June 9, 2011

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