![\"\"](\"https:\/\/flyfiesch.com\/wp-content\/uploads\/2017\/06\/2017-6-26-case-study-synoptic.jpg\")
<\/a>UK Met Office synoptic chart<\/p><\/div>\n
On this synoptic chart, I like the weak high pressure and reasonable spacing between the isobars, but not the cold front lurking to the north.\u00a0 I’m concerned that if that pushes in earlier than expected, high cirrus could shut down solar heating, or valley winds could suddenly pep up.<\/p>\n
<\/a>Google translate version of SRF forecast<\/p><\/div>\n
I’m pleased with this SRF forecast (the term “spring cloud formation” means cumulus development).\u00a0 It’s showing a great lapse rate, and the expectation of the first local showers from mid-afternoon with storms in the evening doesn’t bother me at all; this is typical of good days in the flying season.\u00a0 The prediction of cloud appearing in the southwest towards evening inclines me towards a one-way trip to the east rather than a triangle heading towards the Rh\u00f4ne valley in the afternoon.<\/span><\/p>\n SRF general diagram<\/p><\/div>\n The SRF chart confirms the verbal forecast………….<\/p>\n SRF forecast for Eggishorn<\/p><\/div>\n ………….and their details for Eggishorn (Durschnittl means the average values, and B\u00f6enspitzen the gusts) suggest more wind early in the day than I’d like to see, but not that it will be too breezy for safe flying.<\/p>\n Meteoblue forecast for Eggishorn<\/p><\/div>\n Meteoblue (as usual) shows lighter winds than the SRF prediction, but I hope the storms won’t kick off as early as suggested here.<\/p>\n Meteocentrale N\/S pressure difference chart<\/p><\/div>\n The pressure difference chart causes me some concern. The peak value is below my rule-of-thumb limit of 4 hPa, but a very steep change from north to south overpressure, as shown here, can be associated with the sudden onset of f\u00f6hn<\/a> or other unexpected winds.<\/p>\n Flugbasis winds at 3000m at 2pm<\/p><\/div>\n The Flugbasis forecast for winds at 3000m at 2pm looks good to the east of Fiesch, but that yellow streak on the far left (the Rh\u00f4ne valley) <\/span>reinforces my initial feeling that a flight over the passes towards Chur would be a much more enjoyable prospect than a triangle involving a headwind battle to the west.<\/span><\/p>\n Flubasis winds at 2000m at 2pm<\/p><\/div>\n However, the corresponding chart for 2000m chart suggests some south wind pushing through from the Nufenenpass and Gotthardpass, which could produce dangerous conditions at those points.<\/p>\n Flugbasis wind arrows at 7am<\/p><\/div>\n At 7am, this chart of the actual winds rings an alarm bell – the blue arrow pointing at the “e” of “Schweiz” is the wind at the Grimsel Hospiz.\u00a0 I click on it for more details:<\/p>\n Wind values for the Grimsel Hospiz<\/p><\/div>\n I’m not very happy with this wind strength, but I note that it is forecast to drop to an acceptable level by mid-morning, the earliest that I’d be able to arrive here.\u00a0 As I’m considering a flight to the east, I also check out the values for G\u00fctsch, above Andermatt:<\/p>\n Wind values for G\u00fctsch<\/p><\/div>\n These values are also a concern, but there is a substantial funnelling effect at the location of the anemometer here, often resulting in much higher readings than the true wind speed away from terrain, so I consider that being able to stay upwind in this area without difficulty should be a reasonable prospect.<\/p>\n Emagramme for Payerne at midnight<\/p><\/div>\n The emagramme suggests that there could be a stable layer around 3000m, leading to a slow start to the flight, but is otherwise favourable.<\/p>\n Summary<\/span><\/p>\n This looks like a good flying day to me, but it’s certainly not risk-free.\u00a0 The steep change in the north\/south pressure difference could produce f\u00f6hn<\/a> or other troublesome winds, which may not be obvious from high altitude.\u00a0 Southerly winds could be funnelled through in the vicinities of the Nufenen\/Grimselpass, and of the Gotthardpass (i.e. around Andermatt).\u00a0 I’m less concerned about the risk of overdevelopment, as this is easier to identify whilst airborne than are valley winds.\u00a0 The forecast of cloud in the southwest and a brisk west wind at 3000m in the Rh\u00f4ne<\/span> valley motivates me towards a one-way trip over the passes to the east, rather than a triangle.<\/p>\n Outcome<\/span><\/p>\n Here are the details of my flight:<\/p>\n Flight over the passes on 26\/6\/17 (click here<\/a> for Doarama visualisation, here<\/a> for XContest details)<\/p><\/div>\n I arrived at the Heimat takeoff to find a cloudless sky, but regular thermic cycles already established, and took off shortly before 10am.\u00a0 The climbs were weak and bitty, petering out at an inversion around 2700m (as one would expect from the emagramme), so it wasn’t until three quarters of an hour later that I felt I had enough height to cross to Bellwald.\u00a0 Only a single small cloud was visible ahead, over the 3500m Galmihorn, half way up the Goms, showing an obvious effect of wind from the south (see the header image on this page).\u00a0 There was a southwesterly breeze of around 10 km\/hr along the Goms, and the thermals remained fragmented, with an apparent inversion around 3000m (still consistent with the emagramme).\u00a0 When I reached the Sidelhorn, it appeared that (as expected) the Grimseler<\/a> was absent, as there were only light ripples on the Totesee (the lake in the col of the Grimselpass).\u00a0 The lazy rotation of the wind turbines near the Nufenenpass (in an anticlockwise direction from my point of view), showed no evidence of a breakthrough of excessive southerly airflow.\u00a0 It was an easy decision to continue to the east rather than to turn around and push back against a headwind which would be likely to strengthen the farther I progressed.<\/p>\n I succeeded in breaking through the inversion to reach cloudbase at 3500m, and found that my drift at this altitude was never more than 20 km\/hr from the south, within my comfort zone.\u00a0 The air was buoyant and it was easy to progress over the Furkapass and then to continue along the Urserntal.\u00a0 Approaching Andermatt, I could see that the speed of rotation of the wind turbines at G\u00fctsch indicated a brisk southerly breeze there, although I was experiencing only a gentle tailwind of around 10 km\/hr from the southwest.\u00a0 I stayed well upwind and was able to reach the sunny slopes before the Oberalppass without any drama, where there was very little drift, and I connected with a smooth 5 m\/s thermal to take me back up to 3500m and into the Surselva with plenty of ground clearance.<\/p>\n The next 20 km were straightforward, with small scattered cumulus marking good climbs and a 10-20 km\/hr drift from the south-southwest, but I could see no further clouds beyond Brigels on either side of the valley.\u00a0 Turning around into the wind was not an atttractive prospect, so I decided to press on in the hope of usable lift ahead, but found only wind drifted scraps, and ended up landing by the station at Castrisch<\/a> in a light westerly (although the normal valley breeze there would be from the east), having clocked up just over 100 km in under five hours.<\/p>\n Conditions had been much as expected, apart from a dearth of clouds when I had anticipated concern about overdevelopment!<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Here’s a real life example, setting out my thought processes as I worked through my suggested links to assess the prospects for 26th June 2017, followed by an account of how things actually turned out.\u00a0 Unfortunately, some of the web … Continue reading <\/a><\/a><\/a><\/a><\/a><\/a><\/a><\/a><\/a><\/a><\/a>