thunderstorm system - acid smell - hen or egg?
 

flying through extended weather system over indian ocean.

new generation radar with 2 beams in automatic mode plus calibrated position shows green with diameter 100nm with embedded spots yellow about 10% distance 80nm.
manual mode minus 1 degree shows only 5% green clutters.

deciding to fly straight ahead.

going back to auto mode yellow range increases to 80% when approaching plus about 5% red embedded and quickly changing position while manual mode with minus one shows black only.
only light turbulance but beside st elmo's fire strong acid smell which reminds clearly of volcanic ash smell experienced during catania operations with etna activity.

calmed down worried cabin crew with "this is normal over storm system" but asked myself:
is it possible that these systems can form when volcanic ash from far away - merapi - meets certain weather conditions?

looking for practical advice regarding penetration of volcanic ash clouds such as:
1. st elmo's fire means dry dust is around which harms aircraft systems when lasting;
2. constant st elmo's fire of more than xy minutes can fail your engines...

The eggy smell is sulphur dioxide, quite common in volcanoes.

Have a read of this: TEMIS -- Sulphur dioxide from volcanic emissions

Mike.

The smell, could it have been ozone ?

I'm not sure if you're wondering or just describing the difference between WXR displayed when changing from MAN to AUTO and vice versa.

the AUTO mode usually provides an optimized WXR picture by taking the different components of the radar beams and combining them in a single picture.

The overflight protection feature, which is available only in AUTO Mode, is usually the reason for the different picture you get when selecting MAN.

Many (not implying that you are one of them, just been thinking about this topic for a while now) are not keen to understand how new Multiscan WXR radars and their automatic features work, when a similar situation to the one described above is encountered, the quick judgement that the Auto mode is not accurate or is not reliable is what usually leads to using only the Man mode until the weather is cleared, doing so wastes a lot of expensive and safety enhancing features available only in the automatic mode.

please share your thoughts and tell me if I am overlooking anything with regards to benefiting from the Auto mode ...

(I apologize for the slight drift :) )

shift in sop
 

initially were told to do exactly this (if in doubt about severity, use manual mode) but of course am still not a pro in auto mode, especially do not believe a big system should change color from green to yellow within 5 minutes when approaching. have read manuals on internet but main question beside "avoid red" stays:
avoid or accept yellow when not a cell but "all yellow" within a huge area?

initial question about meaning of continuous st elmo's fire still open...

That's exactly what I would have thought.

St Elmo's doesn't have to be caused only by dry dust particles, in fact, I tend to associate it more with snow and/or ice particles causing the static.

Hydrogen Sulphide is the gas that is commonly associated with rotten eggs.

I think of weak concentrations of ozone as being the 'photocopier smell' but i'm not sure if that's accurate?