Local Wind Forecasting
Not many surfers realize the effect the Tweed valley has on local winds.
Many times I have checked the Byron Bay weather station in winter and the early morning wind is NW, then checked the Coolangatta weather station and the wind is SW.
Last friday morning Byron was reading east while Cooly was recording a light south wind, while the east wind was dominating the bigger picture (and messing up the swell), the localised effect of the Tweed Valley storing cooler air overnight causes the winds at Cooly to be more S/SW.
The Tweed Valley is a U shaped valley with the top of the U facing east, also the southern leg of the U is longer than the northern leg.
I live inland up on the edge of this valley and in winter all the cold air settles down into the valley, the smoke from my chimney comes out at a right angle due to this air flow.
I was hoping for possibly some cleaner lines from ex cyclone Thomas monday.
The swell at Byron on friday was noticably weak and powerless.
Sir....do you mean Tomas or Ului when you talk about swell on Monday? Tomas was out of our swell window by mid last week, so I'm struggling to see how we'll still see swell from him tomorrow?
Leftover Ului swell on the other hand!!
And hambone, predicting offshore early morning winds is a science with alot of factors to take into account, including such things as Sir above has alluded too. One has to look at geographical factors, direction and strength of forecast local synoptic winds, and minimum overnight land temps with respect to current sea surface temperatures.
Geographical effects take years of experience to understand so I'm not going to even try and attempt to generalise those. Generally, if local synoptic winds are forecast to be below 15 knts, and minimum overnight land temps are forecast to get down to less than 4 deg (or more) less than the current sea surface temperatures, then one could assume generally with a rather high degree of confidence that some form of an offshore breeze could well be expected at dawn.
We just need this cloud to bugger off tonight, minimum overnight temps to get down to 19 deg and booyah!!!
Was thinking if any swell got here from Thomas it would take about 5 days to get here.
The Tweed Bouy shows no sign of it, so I am wrong about that one.
I wonder what has happened to the Byron bouy, it hasn't worked for weeks.
Hi Hambone, Yehudi and Don have outlined some excellent reasons for indicating an early inshore land breeze. Monday morning did in fact have a very tasty mix of offshore breeze and leftover Ului swell. Hope u got amongst it. It's a balance of probabilities call on many occassions but Don and Yehudi have covered the basic methodolgy I follow.
Dear Steve Shearer,
I don't get it. The BOM says it's gonna be E winds next week, the synoptic pattern looks like it'll be E, or at least onshore in some capacity, and you say we're gonna get light offshores on Monday and Tuesday early morning as the TC Ului swell drops - sounds PERFECT. But who will be right? My heart is with you, but my head is with the BOM... let's hope I get at the crack on Monday and walk outside and the air is chilly and dewy, then I'll know to check my local just north of Byron to see a SW offshore lighting up that beautiful leftover peak fest that TC Ului has provided.... yum. I'll let you know whether my vision comes true.
HBone