Austrian Arena

How to Assault the Ahorn Spitz, 2968m.
Over the many years guiding pilots around the valley I have to say that still one of my favourite & awe-inspiring flights is making it up the Ahorn Spitz. This flight is both impressive and very accessible for lower airtime pilots.

When is it possible?
On a good thermic day between early May - early September the valley wind is noticable from late morning onwards. Depending on the time of year it will normally peak at between 17-1900hrs.

As a rule I try to avoid landing in the vallley at this time. The strongest time time of year is June & July. Generally speaking the better the day the stronger the valley. Some factors can affect it’s strength, stronger meteo winds help support it.

Usually it is around 1-1200m thick & very bouyant as it has had to travel many kms over baking fields to reach us.It is not uncommon for it to peak at the almost our trim speed in some accelertaed areas. Thunderstorms forming else where can produce a very strong valley wind & should be treated with respect. There are a few exit points for this flight around the valley, however, the following article was from our house mountain the Penken.

The Assault…

This flight first requires a relatively thermic day which has pulled enough air in from the flatlands. The first step is launching on the Penken(picture 1). The valley wind blows directly up this launch site. British pilots will feel right at home on strong days as it’s possible to play with the glider sitting overhead in the 20+kmh wind.

Once away from the hill it’s a straight glide along the ridge to the east(picture 2).It’s possible to pick up a little altitude on the way along. Looking towards the south you’ll locate the Ahorn Spitz, it’s 3 westerly spurs plus the main soarable face(picture 3).

If the valley wind is strong enough to soar it’s also strong enough to create some pretty impressive sink/rotor on the lee sides of the lower spurs of the Penken mountain. These should be avoided if you want to remain safe & high enough to connect easily with the ridge lift on the main face.

If high when you connect with the Ahorn ridge you can head straight towards the house thermal at the cable car pylons to the left of the Wiesenhof guesthouse(picture 4), however, sometimes you’re happy when you come in at the height of the house. If low here turn left and stay on the steepest part of the slope. Soar like you would a hill in the UK. Ideal for low airtimers you want to perfect their technique while being able to wait for cycles as they come through.

If the wind & thermals are good pilots should quickly find themselves topping out above the Wiesenhof, (picture 5). Now is a good time to move to the 2nd ridge just below the Filzen start place. Expect to lose very little on the glide as the steep cliffs to the right of the picture produce good lift. I very often use these to give myself plenty of clearance for searching for a thermal on the west facing spur.

At around 1700m and slightly to the left is a huge scar, very visible in Picture 6. When condtions are a little tricky and stable this scar regularly produces strong enough lift to get through the inversion, (if one is present).

It’s important to stay windward to the valley flow at all times, generally in the afternoon low in the shadows is a bad idea as you could easily find yourself being rotored in the lee. This is all pretty simple until you reach around 22-2300m as pilots will then find themselves in the meteo wind. According to the wind there are different routes to stay safe in the high alpine.

On this day there was a moderate north-westerly. Which enabled easy soaring up the main face(picture 8), this doesn’t work with another direction and can become dangerous with an easterly. This is were the local knowledge is King.

Depending on the meteo wind direction there are some obvious bowls and into wind triggers to the north of the peak. In a northerly pushing round the corner to take advantage of the dynamic lift there is never a bad idea, (picture 9). This is a great part of the flight as you can almost touch the cross on the summit. If you’ve chosen the right side of the peak with the wind blowing up it then getting above the summit is just a matter of making soaring beats or circles.

Picture 10 shows us level with the Ahorn Spitz, I flew away from the mountain to give it a sense of scale against the surroundings. Also taking photos in active air close to big rocks is not always advisable.

Picture 11 shows us over the Ahorn Spitz at an altitude of 3200m, base this day was around 3400m and thermals ranged from 1-5m/s. Once high and away from the terrain it’s time to sit back, relax and take in the views. On a clear day the Pinzgau valley to the north east is clearly visible as are the Dolomites to the south.

Picture 12 shows the Stilluptal and it’s 3000+m peaks that meet up at the end with the main ridge of the Alps and the border with Italy.

Although soaring up in the valley wind is pretty simple the last 700m or so of the assault can be technical. It does required previous knowledge of higher level winds and a little alpine awareness. Please ensure that you understand the conditions and remain safe at all times if you attempt this flight alone. Pilots who join one of our courses will of course be pre armed with the necessary info and will stand a much better chance of completing the flight safely.

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See the movie here

An Introduction…
I’ve been living in the Alps since 1995 and one question that is often asked by our clients flying here is ‘what is the foehn’. In my early years of flying I read the excellent ‘Touching Cloudbase’ but they only glanced on this phenomenon. Over the past years I’ve experienced the Foehn from the air and more safely from the ground. So I thought I’d pen a short article about it, hoping that pilots outside the Alps will learn a little about how to keep themselves safer in the mountains.

Several times I’ve landed early due to an expected foehn and still see pilots hacking themselves off the hill with little knowledge of what’s in store for them if this wind suddenly breaks thru. A lot of it is monkey see-monkey do, they’ve just seen someone land so it must be safe to fly. Little do they know that 30mins can mean a sedate glide turns into a full SIV programme with the pilot becoming just a spectator with little or no control over what’s going to happen. Luck takes over.

The Run up to the Foehn…
The Foehn is caused basically when a strong, humid air mass flows perpendicular to a mountain range, in our case the Alps.
Usually the classic pattern of weather over the Northern Alps goes like this, after a cold front passes thru the airmass becomes unstable. A high pressure with dry air moves in, cloudbase rises, thermals are good and the wind is light and usually from the N,NW in the beginning, slowly backing. As the High moves east across the Alps and the wind slowly switches W. Conditions around this time are still good gets more stable as the warmer air comes from the Southwest, slowing the thermals down. With the next Low over the W, NW of Europe a southerly stream will reach the Alps after it has crossed the Mediterranean and gained a lot of humidity. Once the wind switches to it generally gets stronger with the approaching low. A dry, warm turbulent wind blows on the North side of the Alps, Foehn storms can easily exceed 130kmh. Definitely unflyable!

Sometimes this wind is just a laminar south wind and is soarable if not too strong, usually the air is unstable and thermals help slow the wind down. Also with an unstable airmass the wind is allowed to go over the Alpine Divide or Main ridge unhindered.

However if the air is too stable after the high pressure, there could be inversions in the higher level, then this wind is squeezed and accelerated over the main ridge of the Alps, around 3-4000m high. As it tumbles it creates a massive rotor which can extend for 20-30km. Even more dangerous is if lower inversions break and this rotor is allowed to run through the valleys. This wind then rotors again as the terrain changes direction. This wind will persist until the front arrives restoring a more equal pressure on the north and south side of the alps, cloudbase will drop & the wind in the valleys will change to a strong damp gust front and after the front pass thru a High will usually build again.

The same happens on the south side when the north wind is strong from a low to the North. The Northern Alps are damp with a low base and in the south the North wind howls over the Alps and makes for very turbulent flying.

Why is the Foehn warm?
The reason why the Foehn is dry is easy to explain it’s due to most of the moisture being deposited on the Luv, windward side of the ‘Alpine Divide’ as rain. The reason why it’s warmer at the same altitude in the Lee than the Luv is a little more complex. It’s to do with the difference in Saturated and Dry Adiabatic Rates. Physics tells us that dry air will lower by 1deg/100m climbed. Saturated air ie. cloud will only lower by 0.65deg/100m.

Upon reaching the Alps the air is forced to rise, the humid air saturating fairly early. At the height of the mountain tops the air mass will have lost most of its humidity through precipitation. The sinking on the other side of the mountains and associated warming takes place with the dry-adiabatic lapse rate. At 1000m on the south side the tempertaure is 21degrees but at the same altitude on the north side it’s around 27degrees. The air has warmed up during descent at a rate higher than the cooling during ascent and reaches the plains as a very dry, very warm and very strong wind - the Foehn.

The Foehn is not good news in the winter either as this warm dry airflow eats snow like you wouldn’t believe. Partly due to the tempertaure but mainly due to the airs ability to absorb moisture. Like a dry sponge. The native Americans used to called this wind the ‘Chinook’, or snow eater.

So what does it means for Paraglider pilots?
The worrying thing about the Foehn it that it’s not the wind strength itself, long ago I used to think that if it goes over 30kmh that’s fine my glider goes 50kmh so with speed bar and ears and I’ll go forward no problem. Experience has shown me otherwise. The air in the Foehn is not a laminar air flow as is normal in the Alps but a gusty, twisting rotor that can produce some serious sink, lift and extreme turbulence. It’s a little like flying in out-of-phase wave. Only the mountains which are starting this wave are over 3000m high. It feels like you are always flying in the Lee, which of course you are. It’s almost impossible to accelerate the wing in these conditions, infact without extensive use of the brakes the glider probably won’t stay open long. Saving grace of the Foehn is that it’s mostly short lived and relatively easy for the forecasters to predict. Plus we have several ways of telling if the Foehn is ‘in the post’, mountain stations and near by lakes.

Final Word.
The Foehn can break thru very quickly, a pressure difference of just 4-5Hpa between the North and the south sides of the Alps is enough if the other conditions are in place to produce the squeeze and rotor. Sometimes the wind can even be felt in the valley before it’s felt on launch or between two inversions lower down, these are not ideal situations. Even a slight shift in the wind direction in the high level or the arrival of a nearby front can produce massive rotor in the valleys. So if there is Foehn in the forecast please be careful and if in doubt don’t fly as it’s just not worth it.

Here is some great time lapse of the foehn as it gets ‘Stau’d’ on the main Alpine divide

Here is a short video explaining the foehn

Here is a short computer simulation of the foehn, all be it this is what happens by North Foehn but interesting anyhow.