Darn, missed out on flying Sat morning (again!). What did I do wrong?!
1. FAFK 5:30am: wind 0-2kts, temp 9deg, humidity 91%
2. FAFK 6:30am: wind 0-2kts, temp 7deg, humidity 93%
3. Reported dew point for Cape Town 7deg
4. Cape Town city bowl covered in thick fog, ships continously sounding fog horns
My conclusion: trend at FAFK, temp dropping to dew point, eventually reaching dew point, humidity increasing, fog everywhere else there's gotta be fog at FAFK too. Decision: stay put at home and keep looking at the sky, try for the evening. WRONG!!! Turns out FAFK was open, guys were happily flying
What did I do wrong?!
The definition of dew point is: "The dew point or dewpoint of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for the water vapor component to condense into water." This is all cool, remembered from the met training. What I missed was the following: "The dew point is associated with the relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. If the relative humidity is 100%, the dew point will be equal to the current temperature."
So there we go - humidity was not 100% therefore the 7 deg warm parcel of air above FAFK had no reason to condense into fog and I should have came up with a better excuse for my laziness ...
Right now rain has just stopped in Cape Town ...
Met refresh - Dew point
- Biggles
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Slightly off subject but something that has been nagging at me...
I have noticed that FAFK sits in a funny micro-climate. Paarl is howling, Parow is howling, FAFK ground is dead still, but at circut height its a washing machine. My theory is that you get a plug of cold dense still air that sits in the valley and the wind higher up slowly erodes this air until by 11 the wind is at ground level. This different parcel of air also means that it will have different characteristics than the rest of Cape Towns air.
Micro-climates seems to have more impact on us microlighters than regional weather... I had to endure the guy at weather station telling me to moth-ball my microlight till next year and then going on a beautiful cross country the next day, because I went early and kept away from the hills.
Aswell FAFK weather station regularly lies about wind speed, I have noticed
Slightly off subject but something that has been nagging at me...
I have noticed that FAFK sits in a funny micro-climate. Paarl is howling, Parow is howling, FAFK ground is dead still, but at circut height its a washing machine. My theory is that you get a plug of cold dense still air that sits in the valley and the wind higher up slowly erodes this air until by 11 the wind is at ground level. This different parcel of air also means that it will have different characteristics than the rest of Cape Towns air.
Micro-climates seems to have more impact on us microlighters than regional weather... I had to endure the guy at weather station telling me to moth-ball my microlight till next year and then going on a beautiful cross country the next day, because I went early and kept away from the hills.
Aswell FAFK weather station regularly lies about wind speed, I have noticed
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