Virga

[John Baker]

So yesterday I take off from French Valley headed back to Montgomery Field, VFR. I had decided to take the inland rout and fly over Ramona and approach MYF from the east.

On the way out to F-70 from MYF I had noticed a lot of virga under dark clouds out over the mountains to the east.

My thinking was I would not like to be anywhere near that virga because it could represent some strong downdrafts.

Not a good thing, thought I.

Anyway, we had just crossed over Temecula when I noticed that directly ahead it was dark, and very hazy about a mile or less in front of us. Then the lady that was with me said it looks like rain ahead of us.

I looked to the west, it was cloudy out over the ocean, but I headed that direction with the plan to call SoCal and get clearance through Bravo directly to MYF following interstate 15.

So that is what I did, we were back at MYF with no further problems.

So my questions are, does virga always represent strong downdrafts? Was I being prudent avoiding it?

John

 

[poadeleted20]

No, and yes.

 

[gkainz]

I waved as I drove by French Valley about noon, on my way from Hemet to Sandy Eggo ...

 

[John Baker]

Yea, I saw you, so I honked my horn as I was approaching to join the downwind for 18.

John

 

[gkainz]

I heard it! Sounded like a stall horn!

 

[John Baker]

OK, thread fail. Let me try again. Anyone ever had a bad experience flying into or below virga?

John

 

[Clark1961]

OK, thread fail. Let me try again. Anyone ever had a bad experience flying into or below virga?

John

Last trip out to DWX I looked up and saw a rainbow. Said to myself "this might not be good." Also noticed the rainshaft was nearly non-existant so pushed on through. Didn't get wet but did get the ride down at about 200 fpm while at cruise power and 90 knots indicated (should have been ~110 knots indicated but the autopilot was trying real hard to hold altitude). I was about 3,000 agl and had power in reserve if things had gotten nasty.

Will there always be a downdraft with virga? Well, evaporating water takes heat from the air. Cool air is dense and tends to sink. Will the downdraft be strong enough to kill you? Maybe, maybe not. Look at what's there and decide how much air is likely to be moving down.

 

[Teller1900]

As Ron said, it's not always bad. If nothing else it can be good for a free plane wash. I have flown, several times, under, through, around, and over all manner of rain/virga. Sometimes it's a little choppy, sometimes not. Sometimes you get a little kick in the butt, and other times it just gets a little louder. I don't know why the difference (Scott D?), but it has never been too much of an issue, IME.

There's a very good change, in fact, that I flew through the same stuff you were seeing. I was in MYF at 11am and again at 3pm yesterday. Parked over at Crowne Air.

 

[schmookeeg]

OK, thread fail. Let me try again. Anyone ever had a bad experience flying into or below virga?

John

I was once vectored and held high at an altitude that put me through virga which had some mod++ turb, and it was in and out of IMC at ~28F OAT. This was on approach to Billings from the West at like 13k.

If I had gotten so much as a snowflake's worth of ice accumulation, I was loading the "E" word for a descent out of the clouds ASAP -- as it was, I missed it all, and just endured a nasty ride in and through all the tentacles.

I have never experienced pleasant virga, and the degrees of turbulence I've experienced vary between "huh, that wasn't so bad" to "w-w-w-why d-d-d-d-didnt I d-d-d-d-drive today?" -- I always slow to Va before I tangle with them.

They look like jellyfish for a reason.

 

[BillTIZ]

Will there always be a downdraft with virga? Well, evaporating water takes heat from the air. Cool air is dense and tends to sink. Will the downdraft be strong enough to kill you? Maybe, maybe not. Look at what's there and decide how much air is likely to be moving down.

Exactly! Perfect description of what is happening. How severe the downdraft from the sinking air is hard to predict. If that Virga looks really dark and extends half way to the ground, I would stay far away. Can you see above the cloud it is coming from? If it is a tall CB, it is more likely to be bad and the Virga turn into a real downburst thunderstorm rain shaft.

If it's not looking that bad, can you see dust being kicked up on the desert below it? If so the cold air has already reached the surface and spreading out, think of an upside mushroom cloud with the terrain bounce adding to the turbulence.

Light Virga may be nothing more than a light shower to wash the plane. But will it increase before you get through it? What was the local convective forecast? So many variables.

 

[John Baker]

.

There's a very good change, in fact, that I flew through the same stuff you were seeing. I was in MYF at 11am and again at 3pm yesterday. Parked over at Crowne Air.

I left KMYF around 1:30 then I left French Valley at about 3:30. My guess is that was the same stuff alright. I landed at MYF at 4:00. I remember commenting to Mary that the flight only took half an hour.

I'm way too new a pilot to be messing around with spooky looking stuff in the sky. Even though you obviously survived the horror of it all, probably because you know what your doing, I will continue to avoid it, probably because I only have a rough idea about knowing what I am doing.

The virga stories are starting to get interesting though.

John

 

[John Baker]

Another thought. I have a Garmin Aera 510. I've been waffling about getting signed up for the basic weather package, around $35.00 a month. I'm waffling for two reasons, economic, and the fact that I'm living in San Diego. It is rare when weather is a big issue for my VFR flying. I usually call FSS if I'm going to spend anything more than an hour up.

So....if I had weather hooked up to my 510, would it have been of any help in my decision making regarding the virga?

John

 

[BillTIZ]

So....if I had weather hooked up to my 510, would it have been of any help in my decision making regarding the virga?

John

NEXRAD wx displays are not current, there is an article in this months AOPA (I think it was AOPA) about the latency of the display, how long it takes to build the picture and get it out into the system.

By the time the Virga is picked up, processed and displayed, it could be all over. That's why you are not supposed to use NEXRAD data for real time weather deviations.

 

[John Baker]

NEXRAD wx displays are not current, there is an article in this months AOPA (I think it was AOPA) about the latency of the display, how long it takes to build the picture and get it out into the system.

By the time the Virga is picked up, processed and displayed, it could be all over. That's why you are not supposed to use NEXRAD data for real time weather deviations.

This kind of makes NEXRAD sound pretty much worthless for in flight weather information, more like something you could get on your home computer before you left.

What is the point of it then?

Understand, I have never used it before or even seen it being used, I have no clue about it, which is why I brought the subject up in the first place.

John

 

[Teller1900]

I left KMYF around 1:30 then I left French Valley at about 3:30. My guess is that was the same stuff alright. I landed at MYF at 4:00. I remember commenting to Mary that the flight only took half an hour.

I'm way too new a pilot to be messing around with spooky looking stuff in the sky. Even though you obviously survived the horror of it all, probably because you know what your doing, I will continue to avoid it, probably because I only have a rough idea about knowing what I am doing.

The virga stories are starting to get interesting though.

John

Oh it has nothing to do with knowing what I'm doing. I credit it all to 850SHP (x2) and a five point harness. Onboard radar helps a lot, too.

 

[dmccormack]

This kind of makes NEXRAD sound pretty much worthless for in flight weather information, more like something you could get on your home computer before you left.

What is the point of it then?

Understand, I have never used it before or even seen it being used, I have no clue about it, which is why I brought the subject up in the first place.

John

Simple:

• You can avoid embedded cells when flying IMC (probably the most valuable use)
• You can deviate around closely-spaced gradients that nearly always imply turbulence
• You can get the big picture of the evolving system over time en route

Sure, the data displayed is a few minutes old, but the wx system is moving ~30-50 MPH. You can extrapolate based on past trend and figure out where that red will be now, given where it has been over the past 45 minutes. Give it a wide berth and you'll avoid badness.

That said, NEXRAD plus 'spherics is the best in-cockpit combination, as the StormScope, et al will provide actual, real-time data. Put the two together and you should be able to navigate around badness.

 

[Teller1900]

• You can get the big picture of the evolving system over time en route

That said, NEXRAD plus 'spherics is the best in-cockpit combination, as the StormScope, et al will provide actual, real-time data. Put the two together and you should be able to navigate around badness.

That's the big one! Onboard radar is great, but it often doesn't show you what's behind the big cell in front of you. I can't count the number of times I thought I was being cleaver with a wide open hole between systems only to clear the initial band of light rain and have the whole world close in on me behind the line. Being able to get an estimate of what's behind, while acurately observing what's in front would be an amazing tool.