My Mobile Mesonet

[Joey Ketcham]

Been working on my mobile mesonet today, so far here's what I've gotten so far.

[Broken External Image]:http://216.110.165.36/car1.jpg
[Broken External Image]:http://216.110.165.36/car2.jpg
[Broken External Image]:http://216.110.165.36/car3.jpg

 

[Greg Campbell]

What's with the large base rectangle? Are you planning to mount one of those TAP 2 state-of-the-art portable weather observatories?

Seriously, what instruments are you going to install?

-Greg

 

[Joey Ketcham]

It's just gonna be a big dome on it, nothing inside of it.. just for looks mainly... just kidding. N o it's gonna hold my rain guage, gonna use it to mount my scanner antenna's on plus my anemomenter,a dome covered camera that I can control from inside the car that'll be hooked up to my laptop to record video and also a going to mount an external TV antenna onto it. Mainly just to keep it so I don't have to mount so much to my permanantly.

 

[Chris Sokol]

A quick heads-up...everybody that I have known that has used magnets to install there wx-station has had the same problem...gone with the wind. You definately need some type of strap system...Wal-Mart has a set of strap-on roof racks for $20. I had a station based on these for 3 years and never had a problem. Also, the foreward mast will need a brace running at an ange from the mast to the rack, and also one from the foreward section to the mast. PVC will flex and break if not braced. I am curious...is the mast where you intend to put the anemometer?

All in all, not a bad basic design.

 

[Joey Ketcham]

Thanks for the advise Chris, I know what you mean about weather stations that went "gone with the wind". About 6-7 years ago I made a weather station that was basically a single PVC pipe that held a anemometer and barometer and when I tested it.. of it went..

It's still in the workings, that was just what I got done yesterday, my weather station is coming in on Tuesday so I'm gonna finish it then.. including adding front brace supports to the mast

And yes, the front mast is where I'm going to be placing my anemometer at and across the base I will have a thick sheet of plexiglass that will hold other stuff.

 

[Greg Stumpf]

Originally posted by jketcham
Been working on my mobile mesonet today, so far here's what I've gotten so far.

The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think "wind tunnel"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.

Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.


Greg Stumpf, Norman, OK

 

[Joey Ketcham]

Greg,

Thanks for the reply and for the advise. I never thought of the airflow and how it'd affect my readings.. but definately makes sense now and I'll get that corrected.

As far as a weather logging system, it's a done deal. I bought a software package with the weather station that will continuously log weather conditions in and around the storm onto my laptop and archieve it with time and date stamp so I will definately be contrubiting that info the NWS and to the rest of the community.


Joey

 

[Bill Hamilton]

Originally posted by Greg Stumpf
Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.

Once he gets his HAM license it will make real-time reports easier to report to the NWS. As far as the mobile meso it will be refined and trustworthy by the next storm season I'm bet. Trial and error will work the kinks out but it is a good start. I am curious to see his final project.
I'm not to crazy about a sunroof in a storm chase vehicle because I have had one shatter before but that is another story. I would use film tint on it though to help keep you from wearing it.

 

[John Diel]

Anemometer placement and Bernoulli Effect

Just in case you are wondering, the principle associated with the anemometer placement and accurate wind reading is the Bernoulli Effect or Bernoulli's Law:

For horizontal fluid flow, an increase in the velocity of flow will result in a decrease in the static pressure. The equation describing this effect is known as Bernoulli's law. The most practical example of this is in the action of an airfoil. The shape of an airplane wing is such that air flowing over the top of the wing must travel faster than the air flowing under the wing, and so there is less pressure on the top than on the bottom, resulting in lift.

Looking at the Project Vortex stuff, they placed their meters 3 meters above the ground level (just over 9 feet). Depending on the vehicle I would think this was about 4 to 5 feet from the top of the vehicle roof. They also said they solved the issue of wind speed measurements while driving, but they didn't say how. I'm betting it was done post chase using the GPS info and vehicle speed rates in some formula.

John

 

[David Sallee]

Looks like a good start Joey.... I'm also interested in seeing the final project .... I'm going to be putting me together one this fall... hopefully.. :wink:

Dave

 

[David Drummond]

Originally posted by Greg Stumpf+--><div class='quotetop'>QUOTE(Greg Stumpf)</div>

<!--QuoteBegin-jketcham

Been working on my mobile mesonet today, so far here's what I've gotten so far.

The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think "wind tunnel"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.

Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.


Greg Stumpf, Norman, OK[/b]

Hey Greg, I know we had discussed some of this via email...I am wondering.....do you guys have ability to see APRS up there? I know some SKYWARN groups use it and if I remember right you can hook APRS up to a wxstation like a mesonet and broadcast that out with it. I seem to remember they guys at MAF telling me they liked seeing all the stationary ones in the area as it was useful in determining various boundary passings etc.

 

[John Diel]

Hmmm.... David brings up and interesting point

I don't see why you couldn't run a packet transmitter during a severe event. I think Columbia Weather Inc. Has one that will interface well enough to do this www.columbiaweather.com but I couldn't tell you for sure. Though their systems are a little pricey for me, they appear to be pretty nice. They even have it thought out for vehicle mounting.

But as far as HAM Packet Transmissions, I don't see why you couldn't. I don't know enough about that area to give a good answer, but I would bet it can be done.

 

[Greg Stumpf]

Re: Anemometer placement and Bernoulli Effect

Originally posted by John Diel
Looking at the Project Vortex stuff, they ... said they solved the issue of wind speed measurements while driving, but they didn't say how. I'm betting it was done post chase using the GPS info and vehicle speed rates in some formula.

GPS was used to subtract the vehicle motion vector from the measured wind in real-time. It is the same concept that R. J. Evans uses in his set-up, while loading up live data to the Web.

However, it was determined that the MMs measured wind best, while "in motion", if the vehicle speed was 40 mph or less, with very little velocity and angular acceleration. We exercised the "smooth, straight, and steady" driving technique when we were taking measurements "in transect" across dry lines or RFD gust fronts, etc.


greg

 

[Greg Stumpf]

Originally posted by David Drummond
...do you guys have ability to see APRS up there? I know some SKYWARN groups use it and if I remember right you can hook APRS up to a wxstation like a mesonet and broadcast that out with it.

Some of the WFOs use APRS to track spotters and grab their wx data. I'm not up-to-date on what the current NSSL technology is for broadcasting vehicle location and mobile mesonet data live to the Field Coordinator (FC) - I'm guessing a combo of satellite and/or 2-meter packet transmission. I know that the FC can see the location and wx of all vehicles overlaid on radar data (WSR-88D, SMART-R, etc).

Perhaps Scharfenberg knows more...?


greg

 

[John Diel]

Good thing I don't gamble!

Hi Greg,

It's a darn good thing I don't bet on the ponies.
I should have known there would be a real-time solution to that issue. I didn't think they would have had it though in that time frame. Makes sense though, if the MM could transmit the data, then the host computer could make the calculation and display it in real-time.

Thanks for the update. I rather doubt that I will ever get that technical in my area of chasing though. I figure I'm updated enough with a GPS and radio!

John