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9 Knot Nige's Weather tips for cross country from Warwick

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Nigel Andrews (23.06.2014 12:56:00):

Hi All,

Just thought I would pass on some trade secrets so as to give you all a fighting chance when I come out and flog the distance record – I hate to see grown men cry – the girls I would expect it. ..read on!

 

RASP and other prediction programs.

Generally they get it right BUT too much faith in computer models can cost you valuable comp points. These rely on other complex computer models and put it in the mix. In the old days we did temp traces and relied on the weather man. Temp traces are good BUT still fall short when systems move in during the day as they only give you the air above at the time you did it – still better than nothing.

So over the 25 years of flying XC on the Boonah and downs sides here are my observations based on surface charts, upper level charts which include the jet stream and beuro farming predictions as well as the SKEW log NOAA data:

Winter highs, high pressure area centred at or just below Qld.  In winter this will cause cold air from the upper atmosphere to descend effectively trapping the warmer air underneath by creating an inversion ( a layer where the air is higher than the ascending air therefore stopping it from going any further) These inversions require a great deal of heat to punch through. Generally the day will be still, frosty mornings with heating mid-day producing weak localised thermals to the inversion height.

Tip – plan for about 2 hours of possible X/C, thermals to 5,000ft maybe higher over mountains. Tip – work weak thermals out of Warwick and aim for trigger points, large brown paddocks, sides of hills in the sun. I always plan to do an airfield to airfield trip, i.e Clifton, Pittsworth, DDSC etc. 2 Hours is normally the usefully time so don’t plan a big one unless it’s going OOOOORRRF.

SE weather – no trough . High down south, airflow going anti clockwise bringing in cool moist air from the coast. Along the coast showers are the norm, they may extend inland if the wind is strong enough. This weather in winter is normally not too good ( without trough) Its usually quite cool on the ground, the thermals will trigger but usually are broken. For some reason the airfield is in a sink hole when they blow. The odd shower may come through.

Tip – If you are determined to go then work whatever you can and get out of there! Again I normally aim for Clifton and then try and go west as the further west you go the better the thermals as the wind strength decreases and the ground gets warmer. Same rule applies, short day = shorter task unless you are just going for straight distance points and outland in which case have a crew ready and if its white ant Scott then just run for the hills unless he’s in the discus.

SE with trough. Sometimes and its happened here recently a lot a weak upper level trough will form up. Upper level troughs are areas of low pressure in the upper atmosphere so the air below will generally be sucked upwards. SE weather with a trough will see lots of streeting with black flat bases. High up you will get strong lift ( in the suction layer) down low you will be in a world of pain, often working lots of gusty cores in the layer of turbulence created from hills, trees etc. because of the wind and colder air so rule is to stay high, work the streets to your best advantage and watch out for the downwind legs that you don’t blow it. Trough days will generally last right up to nearly dark so bigger tasks are possible.

North East to North west In winter they can be better than a SE day as the warmer air from the north comes down, the NW is dryer, NE will have CU. Depending on the ground temp and wind strength you can get more than a few hours flying. North east/NW are more common later in the winter season.

West/SW  Brrrr, cold windy days, Antartic air dragged up from the south. OK without a trough and that’s the norm winter W/SW is usually cold artic winds. You can still get thermals in sheltered areas facing the sun ( Bony mountain east is one example) which will pop off a thermal but it will be dragged a long way downwind. With all streeting  memorise the wind direction and drift and if you loose contact on a STRONG wind day go upwind to find the next, trying to reconnect with it going downwind could drift you beyond safe glides to home or paddocks. There will be wave!

TIP – Contacting wave will get you real high, I have been at 12,000ft in wave over the airfield! Work the hill thermals and get into it, the ranges to the SW and boney all seem to generate the downs wave so go for height, go upwind, go for height etc. You could work an out and return multiple legged track and get some points so don’t give up on westerly days! Also, wave is fun. If you have never worked wave go with someone who has and learn to surf! ( surf doesn’t mean outland downwind on the Gold Coast)

W/SW with trough. Can happen but it’s rare as W/SW weather is usually clearing weather with a low in the bight, again if it does happen work the streets! You might get to the Cunningham wave and catch a lift to 12,000ft ( if Amberley is DE active)BUT going home could be interesting! I have had 50 knot winds in the Cunningham wave ( and been to 18,000ft in the old days ) , all wave systems create rotor of some degree, aim to fly out of this stuff ASAP unless is associated with broken lift which can be very strong.

W/SW – high probability of inversion which can enhance wave but stop thermals from going high – just another double whammy.

So for the experts you already know this so I am not telling anyone to suck eggs, I wrote this for those who lack a bit of confidence in the winter weather which can be great and going ORRRRFFFF

So in my opinion best days are definitely trough days, but all days can score points as you just need to think about the weather and think about the mechanics of how lift works and put it together with your day plan

Cheers

Nige

 

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