Typhoon Question

[sicilian]

Hi guys,

I recently got asked in an interview:

"Why when you look down on a typhoon is there no cloud in the middle?"

Thankfully I did pretty well in the other Q's asked because I had very little idea on that one!!!

Is there any chance someone can give a step by step answer on this one?????

Thanks in advance

[FCS Explorer]

:} it's a trick question! the correct answer is: "i would NEVER fly into a typhoon!"

futhermore cold DRY air is descending thru/in the eye.

[sicilian]

Cheers FCS,

Apologies that this may be a very obvious question but where does this cold dry air originate from?

I understand the prereqisites for a typhoon but just always get a little confused with the actual physical formation process:ugh:

[FCS Explorer]

do the wiki. it knows everything.

[chornedsnorkack]

cold DRY air is descending thru/in the eye.

I do not think so. I think that the air in the eye is HOT and dry.

The answer would start with this:

What goes up must come down.

In an ordinary cyclone, warm moist air rises - drops the rain, reaches the heights as cold dry air - and it has to go down. When it goes down, it ends up as dry air which is warmer than the original warm moist air - because it has gained the heat from the condensation.

In the ordinary cyclone, there is calm wind - because of symmetry - but heavy rain in the dead middle. Around the middle of the cyclone, the air spirals up, causing a windstorm and rain. At the centre, the air goes straight up, causing calm wind and heavy rain.

The air which reaches the upper levels above the cyclone flows out at upper levels, and then descends outside the cyclone, causing warm and dry weather.

This description also applies to weak tropical cyclones.

However, in strong tropical cyclones, so much air builds up at the upper levels above the typhoon that while most of it still flows out and descends in neighbouring areas, some forces its way straight down the middle of the cyclone, suppressing the rain and clouds there. So the air goes up all around the eyewall and comes down both outside the typhoon and inside the eye!

[Dani]

The trick question isn't one:

You can easily overfly a typhoon. Depending on its size. I can show you pictures of them. We saw them very regurarly over the South China Sea.

Dani

[SMOC]

Make sure you can fly over them, the ISA deviation can get very high more the ISA +20

[Blip]

You can easily overfly a typhoon.

You might be the unluckiest pilot in the world but there is also a saying that says you make your own luck...

What if you are forced to descend due to:
Cabin pressurisation issues.
Engine issues.

You might then be facing the situation where you are on one engine (if you are flying a twin), and descending into severe icing, severe turbulence, hail,... ouch!


The other day there was a line of CB, and TCU, that had only a vertical development of about 32,000 ft - 34,000 ft while we were level at 37,000 ft. We chose to divert 40 nm off track and added maybe a minute or two to the total flight time rather than fly over the top.

As remote the possibility that we suffer a malfunction such that we would be forced to descend into the weather that was only possibly 20-30 nm deep, the risk vs reward just didn't justify the shorter route IMHO.

A typical typhoon is how many miles across?:uhoh:

[Dani]

There is no typical typhoon. There are small, medium, big and veeery biiig ones. If you have only a few thousand feets between you and the tops, you check your radar and decide wisely.

The question was about the eye of a cyclone and some smart guys tried to trick him. So I put it into perspective.

Keep it up safely,
Dani

[VRSCSE2]

Sometimes there are clouds in the eye....

http://www.solarviews.com/cap/earth/typhneye.htm


This spectacular, low-oblique photograph shows the bowl-shaped eye (center of photograph) of Typhoon Yuri in the western Pacific Ocean just west of the Northern Mariana Islands. The eye wall descends almost to the sea surface, a distance of nearly 45,000 feet (13,800 meters). In this case the eye is filled with clouds, but in many cases the sea surface can be seen through the eye. Yuri grew to super typhoon status, packing maximum sustained winds estimated at 165 miles (270 kilometers) per hour, with gusts reaching an estimated 200 miles (320 kilometers) per hour. The storm moved west toward the Philippine Islands before turning northeast into the north Pacific Ocean, thus avoiding any major landmass.

[Wonder Boy]

If you do a google image search you will probably find a diagram that will doubtlessly better convey the following explanation:

It is generally cloud free in the 'eye' of a typhoon as a result of the convective structure of the storm. The tubular wall of cloud lining the eye of the storm is where windspeed is at its greatest and also the position where air rises most rapidly; this could be understood as resulting from the fact that the [I]pressure gradient [I] is greatest there (i.e. the isobars are really close together there).

The air surrounding the eye rises and builds substantial cells. However, eventually the air reaches the tropopause and can't continue to rise because of the levelling off of the [I]temperature gradient[I]. When the air reaches the tropopause it is therefore forced to move laterally - most of it moves outwards toward the extremity of the storm. [U]However[U] some of it moves laterally toward the centre. So all this air that converges at the centre of the storm up at the tropopause has to go somewhere: It has 'no choice' but to DESCEND.

As I'm sure you're aware clouds most commonly form when air rises, cools and temperature and dewpoints meet causing condensation of water content to form water droplets.

When air DESCENDS the opposite generally occurs: the air warms, water droplets become vapour and hence the air is 'clear' or 'cloud free'. Hence the gently descending air at the central 'eye' of a typhoon is cloud free.

[chornedsnorkack]

It is generally cloud free in the 'eye' of a typhoon as a result of the convective structure of the storm. The tubular wall of cloud lining the eye of the storm is where windspeed is at its greatest and also the position where air rises most rapidly; this could be understood as resulting from the fact that the [i]pressure gradient [i] is greatest there (i.e. the isobars are really close together there).


But this does not follow! When there is no eye and the air rises most rapidly at the centre (most cyclones), the windspeed still goes to zero at centre (because of symmetry) and the pressure gradient also vanishes there (same reason).

[Wonder Boy]

This is a link to the Woods Hole Oceanographic Institution; It shows a good diagram of a vertical crossection of a hurricane/typhoon:


http://www.whoi.edu/page.do?pid=13515&tid=441&cid=15324&ct=61&article=7673

[Arrowhead]

Check out QRH 4.06

For a 319 at 58T driftdown distance and time from FL370 to FL276 is 360nm in one hour. In other words, probably enough time to escape the typhoon before you hit the top.

A321 at 72T is 380nm 70 mins to FL220 from FL 350. Clearly you would not want to be in this situation.

In other words, flying 7000+ft over the top in a light aircraft is probably not a problem. Flying 2000ft over the tops in a heavy aircraft is taking a chance.

Sadly, trying to get your flight ops dept to understand this may not always be possible.

[sicilian]

Thanks for all the responses guys. Making more sense now.

Cheers