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Trust, but verify your weather

Louise Hose

Well Known Member
I needed to fly from Oshkosh to Anoka County (St. Paul), MN, yesterday to join Paul for a family event today. I knew I was racing west to (hopefully) beat out weather coming from the northwest so I kept my eye on the XM Weather the entire flight. First light green, then dark green, and finally yellow covered my destination. Bummer. About 50 nm out, I diverted my line a bit to the south towards Red Wing (RGK). Oddly, the Anoka METARS didn't mention rain yet, but the area was covered with yellow on the screen.

As I flew, I entered the light green area. No rain and good visibility. Okay, I've seen this before. As I approached KRGK, I listened to the AWOS at Lake Elmo (21D). No rain reported despite dark green. Since Lake Elmo would be much closer for Paul to pick me up, I decided to change course for Lake Elmo. The path to Red Wing remained clear as a potential retreat.

IMG_1119.JPG


A couple miles from 21D and still no rain. Could I possibility make a safe trip to Anoka County (KANE)? I tune in that ATIS and things sounded very do-able. Light wind, light rain, decent visibility. As I reached Lake Elmo, a very light rain started (in what was reported as a yellow area). I called the Anoka Tower and the lonely controller confirmed that the rain was light, winds trivial, and visibility decent. I told him that I would try to come in if the weather remained good.

On the way in, I actually flew through a small patch of area recorded as orange, but I would only call it a steady "soaking" rain. No bumps. No lightening. No issues. The landing was a non-issue.

I found the experience highly interesting and useful. My path always had excellent retreat lines behind me (because I had basically flown from airport to airport). I have once previously flown into an area that turned yellow on me and I didn't like it at all. But, I've learned that light green, dark green, and yellow don't represent consistent conditions. In the humid south Texas, green seems to rarely mean actual rain. Seems the same was true yesterday for Minnesota. Yesterday was a great example of how going out in a strategic manner to find out what the weather data are really telling you, and ensuring excellent escape routes, can get you places that a review of a computer screeen would never have supported.
 
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The returns are actually there at some altitude. I think what accounts for most of the variation is how much moisture there is in the lower levels. There can be a lot of evaporation on the way down. I regularly see yellow around here with nothing hitting the ground (that is back in the days when we used to get rain).

Oh, and always nice to see that famous "Trust but verify" quote!
 
The opposite can also be true.

Until datalink weather gets much MUCH better this is why it won't replace on board wx radar. Great strategic tool, tactically not so much.
 
XM weather is impressive technology but VFR flight and dealing with weather is quite doable without it.

Actually, I find it very worthwhile for VFR flights across the western & mountainous USA. When the weather is marginal, and eyeballs don't see past the next mountain range.............it's a great tool! On a recent trip to Montana, it was worth every cent.

L.Adamson --- RV6A
 
Thanks for the PIREP I think having that knocking around in my head will come in useful someday.
 
A peek is worth a thousand sweeps

I flew from Sumter SC to my home base of Dahlonega last Saturday and encountered the same thing. If I had gone strictly be the XM I would have turned and ran. At 10500 was a pretty good wall of clouds and dark green and yellow on the 496. I descended down to 6500 and had good forward vis and was mostly just dodging rain shafts. On down to 4500 under everything with 8 to 10 miles vis and smooth as glass. All this time yellow and dark green XM.

I always had an out either back east or to the south if what was depicted on the 496 was really what was happening. In this case, all up high and evaporating before coming down low.

XM is a great strategic tool in your bag but I rarely make a decision based just on what it's showing. Used along with all the other tools in your bag it's a great help, but like I said above, a peek out the window is worth a thousand sweeps.
 
The returns are actually there at some altitude. I think what accounts for most of the variation is how much moisture there is in the lower levels. There can be a lot of evaporation on the way down.

Actually in south Texas, I've often seen green when there is no cloud in the area. I'm not sure why but I am sure there is no rain at any level. Seems it happens when the atmosphere has very high moisture in it. Only see it in the hot summer months.
 
I actually employ 4 sources to check wx. On the ground I use a combination of SkyChartsPro to check metars and TAF along my intended route. I then use the Intellicast app to verify what SkyCharts has told me. Intellicast is great because you can "play" the last hour of movement associated with the cells. Lastly, if it is a "Go" situation I use my eyeballs and xm wx.

I concur with what Louise has commented on except I haven't had the unpleasant experience of being in the "yellow" area and not liking it. Hopefully, I will never have that experience. :)
 
A few years back, out here in West Texas, XM really saved the day when two seperate fast building systems moved towards each other, one from my left and one from the right. With a fast RV a 180 degree turn around back 50 miles before going back around the right hand cell made my day.

By the time I got around the right hand cell the area where they came together was Red. I only saw steady rain in the light green area on the back side. Had I been on an IFR flight plan without XM weather I doubt that ATC coverage out here in West Texas would have given me the kid of heads up that XM does.

XM along with knowing what is behind you and a good set of eyeballs during times of hot humid thunder storm building afternoons is great piece of mind. This year I can only dream of humid thunder storm building afternoons. Rain for the year so far is less than one inch (for the year not month!!!).
 
XM is at the top of my Must Have list

For anyone not familiar with XM weather, one of the neat features is being able to activate the screen cursor and get METARS anywhere on the map display by placing the cursor on a weather triangle symbol. The advantage is that you don't have to be within voice transmission range to get ASOS information. Makes it easy to plan diversions from any distance out. Also, since you already know the direction of weather movement, you can use this tool to determine if it's rain or virga moving toward your route or destination. Kind of like getting an updated TAF.
Terry, CFI
RV9A N323TP
 
I have flown into green and yellow areas many times. In addition to Louise's observations what I have learned is if weather is "building" or getting worse you need to really be careful as the weather indicated on XM seems to lag. If the weather is steady or "waning" it is safer to fly though. "Stay away from red, or you might end up dead." ;)

One thing that really helps my CC flights is Winds Aloft. I can usually pick up a tail wind or change a head wind into a cross wind and improve my ground speed.
 
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ADS-B Freebies

For anyone not familiar with XM weather, one of the neat features is being able to activate the screen cursor and get METARS anywhere on the map display by placing the cursor on a weather triangle symbol. The advantage is that you don't have to be within voice transmission range to get ASOS information. Makes it easy to plan diversions from any distance out. Also, since you already know the direction of weather movement, you can use this tool to determine if it's rain or virga moving toward your route or destination. Kind of like getting an updated TAF.
Terry, CFI
RV9A N323TP

One of the things that came out of the ADS-B forum presentation at OSH is that when it all comes to pass, the weather info coming from XM will be free via the FAA and the ADS-B system. The government decided to throw that benefit in the pot to get people to sign on before the mandatory date of sometime in 2020.

All the ground based broad band stuff should be up and running by 2013 so it will be a matter of buying and installing the ADS-B transceiver, avionics display and IFR certified gps to have access to the weather service along with providing all the out information into the system from your flight. This system will ultimately replace ground based radar.

At present about half the country is covered by the system. Four or five companies are working with the FAA on providing a less expensive gps than the certified panel mounted units available today. While current hand held units are WAAS capable and work, they are not IFR certified and do not meet the ADS-B specs for gps. I confirmed that bit of info with a Garmin rep.

I do believe the IPAD display will work with experimental systems now being developed with FAA participation and future certification.

This is one of the companies doing ADS-B development work.

http://www.freeflightsystems.com/prod_adsb.htm

All this of course is dependent on the FAA having a budget that includes money to complete the ADS-B plan. At present congress is grid locked over FAA funding and thousands of FAA people are unemployed. ADS-B may be on the chopping block. It may well depend on how broke our country really is. The reality is, ADS-B may be the funding tool congress is looking for, it will be a simple matter to impose user fees via this system.
 
XM WX

Don't forget to use the "animate" feature to really get the big picture. Trends are valuable to paint the picture. Gene
 
Using the XM weather requires some basic knowledge and a lot of experience with it. I view the information from a ground up perspective...that is, the metars give you useful information about what is happening on the ground at that point, so it is quite useful. Especially if you are flying in an area that has a lot of reporting stations. The Nexrad info is very helpful but delayed and much more general in nature. I pay close attention to the metar report of cloud bases which you really can't get from the XM cloud information.

One thing that can be helpful is the degree of spread, that is, if the green is wide spread around the yellow which is wide spread around any red then you are "less likely" to see any significant precipitation. Give a wide berth around the red stuff (especially if it covers a lot of area). Look at the metars below the green and yellow areas to see what is happening on the ground and pay close attention to how closely spaced the green, yellow and red areas are. If they are tightly spaced, it is probably more significant weather. Don't forget to check the winds aloft in the those areas but remember that they are predictive, not real time.

Keep a good "out" plan but don't be afraid to test the waters. You will learn alot about what the display is telling you. FLY SAFE.
 
I am not usually a fan of safety "courses" presented on the AOPA website but there is one there now on the home page that walks you through the basics and many of the details of datalink weather and how to use it.

It answers many of the questions I often see asked on bulletin boards.
 
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